Technic and Toolranks support (#73)

Co-authored-by: Treer <treer.git@gmail.com>

.luacheckrc

@@ -2,10 +2,12 @@ unused_args = false
 allow_defined_top = true
 
 globals = {
+	"bucket",
 	"nether"
 }
 
 read_globals = {
+	"climate_api",
 	"core",
 	"default",
 	"DIR_DELIM",
@@ -23,9 +25,14 @@ read_globals = {
 	"PseudoRandom",
 	"stairs",
 	"stairsplus",
+	"string.split",
 	table = { fields = { "copy", "getn" } },
+	"technic",
+	"toolranks",
 	"vector",
 	"VoxelArea",
 	"VoxelManip",
+	"walls",
+	xpanes = { fields = { "register_pane" } },
 }
 

README.md

@@ -1,9 +1,32 @@
-Nether Mod for Minetest, with Portals API.
+# Nether Mod for Minetest, with Portals API.
+
+Allows Nether portals to be constructed, opening a gateway between the surface
+realm and one of lava and netherrack, with rumors of a passageway through the
+netherrack to a great magma ocean.
+
+To view the options provided by this mod, see settingtypes.txt or
+go to "Settings"->"All Settings"->"Mods"->"nether" in the game.
+
+A Nether portal is built as a rectangular vertical frame of obsidian, 4 blocks
+wide and 5 blocks high. Once constructed, a Mese crystal fragment can be
+right-click/used on the frame to activate it.
+
+
+## Modders and game designers
 
 See portal_api.txt for how to create custom portals to your own realms.
 
-See settingtypes.txt or go to "Settings"->"All Settings"->"Mods"->"nether"
-in the game to view the options provided by this mod.
+Nether Portals can allow surface fast-travel.
+
+This mod provides Nether basalts (natural, hewn, and chiseled) as nodes which
+require a player to journey to the magma ocean to obtain, so these can be used
+for gating progression through a game. For example, a portal to another realm
+might need to be constructed from basalt, thus requiring a journey through
+the nether first, or basalt might be a crafting ingredient required to reach
+a particular branch of the tech-tree.
+
+Netherbrick tools are provided (pick, shovel, axe, & sword), see tools.lua
+The Nether pickaxe has a 10x bonus against wear when mining netherrack.
 
 
 ## License of source code:
@@ -27,21 +50,35 @@ SOFTWARE.
 
 ### [Public Domain Dedication (CC0 1.0)](https://creativecommons.org/publicdomain/zero/1.0/)
 
- * `nether_portal_teleport.ogg` is a timing adjusted version of "teleport" by outroelison (https://freesound.org/people/outroelison), used under CC0 1.0
+ * `nether_portal_teleport.ogg` is a timing adjusted version of "teleport" by [outroelison](https://freesound.org/people/outroelison), used under CC0 1.0
+ * `nether_rack_destroy.ogg` is from "Rock destroy" by [Bertsz](https://freesound.org/people/Bertsz/), used under CC0 1.0
 
 ### [Attribution 3.0 Unported (CC BY 3.0)](https://creativecommons.org/licenses/by/3.0/)
- 
+
+ * `nether_lightstaff.ogg` is "Fire Burst" by [SilverIllusionist](https://freesound.org/people/SilverIllusionist/), 2019
  * `nether_portal_ambient.ogg` & `nether_portal_ambient.0.ogg` are extractions from "Deep Cinematic Rumble Stereo" by [Patrick Lieberkind](http://www.lieberkindvisuals.dk), used under CC BY 3.0
- * `nether_portal_extinguish.ogg` is an extraction from "Tight Laser Weapon Hit Scifi" by damjancd (https://freesound.org/people/damjancd), used under CC BY 3.0
- * `nether_portal_ignite.ogg` is a derivative of "Flame Ignition" by hykenfreak (https://freesound.org/people/hykenfreak), used under CC BY 3.0. "Nether Portal ignite" is licensed under CC BY 3.0 by Treer.
+ * `nether_portal_extinguish.ogg` is an extraction from "Tight Laser Weapon Hit Scifi" by [damjancd](https://freesound.org/people/damjancd), used under CC BY 3.0
+ * `nether_portal_ignite.ogg` is a derivative of "Flame Ignition" by [hykenfreak](https://freesound.org/people/hykenfreak), used under CC BY 3.0. "Nether Portal ignite" is licensed under CC BY 3.0 by Treer.
 
 ### [Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)](https://creativecommons.org/licenses/by-sa/4.0/)
+ * `nether_basalt`* (files starting with "nether_basalt"): Treer, 2020
  * `nether_book_`* (files starting with "nether_book"): Treer, 2019-2020
- * `nether_portal_ignition_failure.ogg`: Treer, 2019
+ * `nether_brick_deep.png`: Treer, 2021
+ * `nether_fumarole.ogg`: Treer, 2020
+ * `nether_geode.png`: Treer, 2021
+ * `nether_geode_glass.png`: Treer, 2021
+ * `nether_lava_bubble`* (files starting with "nether_lava_bubble"): Treer, 2020
+ * `nether_lava_crust_animated.png`: Treer, 2019-2020
+ * `nether_lightstaff.png`: Treer, 2021
  * `nether_particle_anim`* (files starting with "nether_particle_anim"): Treer, 2019
+ * `nether_portal_ignition_failure.ogg`: Treer, 2019
+ * `nether_smoke_puff.png`: Treer, 2020
 
 ### [Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)](http://creativecommons.org/licenses/by-sa/3.0/)
- * `nether_rack.png`: Zeg9
- * `nether_glowstone.png`: BlockMen
+ * `nether_glowstone`* (files starting with "nether_glowstone"): BlockMen
+ * `nether_nether_ingot.png` & `nether_nether_lump.png`: color adjusted versions from "[default](https://github.com/minetest/minetest_game/tree/master/mods/default)" mod, originally by Gambit
+ * `nether_portal.png`: [Extex101](https://github.com/Extex101), 2020
+ * `nether_rack`* (files starting with "nether_rack"): Zeg9
+ * `nether_tool_`* (files starting with "nether_tool_"): color adjusted versions from "[default](https://github.com/minetest/minetest_game/tree/master/mods/default)" mod, originals by BlockMen
 
-All other media: Copyright © 2013 PilzAdam, licensed under CC BY-SA 3.0 by PilzAdam.
+All other media: Copyright © 2013 PilzAdam, licensed under CC BY-SA 3.0 by PilzAdam.

crafts.lua

@@ -0,0 +1,72 @@
+--[[
+
+  Copyright (C) 2013 PilzAdam
+  Copyright (C) 2020 lortas
+  Copyright (C) 2020 Treer
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+minetest.register_craft({
+	output = "nether:brick 4",
+	recipe = {
+		{"nether:rack", "nether:rack"},
+		{"nether:rack", "nether:rack"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:fence_nether_brick 6",
+	recipe = {
+		{"nether:brick", "nether:brick", "nether:brick"},
+		{"nether:brick", "nether:brick", "nether:brick"},
+	},
+})
+
+minetest.register_craft({
+	output = "nether:brick_compressed",
+	recipe = {
+		{"nether:brick","nether:brick","nether:brick"},
+		{"nether:brick","nether:brick","nether:brick"},
+		{"nether:brick","nether:brick","nether:brick"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:brick_deep 4",
+	recipe = {
+		{"nether:rack_deep", "nether:rack_deep"},
+		{"nether:rack_deep", "nether:rack_deep"}
+	}
+})
+
+minetest.register_craft({
+    output = "nether:basalt_hewn",
+    type = "shapeless",
+    recipe = {
+      "nether:basalt",
+      "nether:basalt",
+    },
+})
+
+minetest.register_craft({
+  output = "nether:basalt_chiselled 4",
+  recipe = {
+    {"nether:basalt_hewn", "nether:basalt_hewn"},
+    {"nether:basalt_hewn", "nether:basalt_hewn"}
+  }
+})
+
+-- See tools.lua for tools related crafting

depends.txt

@@ -1,7 +1,10 @@
-stairs
 default
-moreblocks?
-mesecons?
-loot?
-dungeon_loot?
+stairs
 doc_basics?
+dungeon_loot?
+fire?
+loot?
+mesecons?
+moreblocks?
+climate_api?
+xpanes?

init.lua

@@ -19,6 +19,13 @@
 
 ]]--
 
+-- Set DEBUG_FLAGS to determine the behavior of nether.debug():
+--   0 = off
+--   1 = print(...)
+--   2 = minetest.chat_send_all(...)
+--   4 = minetest.log("info", ...)
+local DEBUG_FLAGS = 0
+
 local S
 if minetest.get_translator ~= nil then
 	S = minetest.get_translator("nether")
@@ -35,31 +42,111 @@ end
 
 -- Global Nether namespace
 nether                = {}
+nether.mapgen         = {} -- Shared Nether mapgen namespace, for mapgen files to expose functions and constants
 nether.modname        = minetest.get_current_modname()
 nether.path           = minetest.get_modpath(nether.modname)
 nether.get_translator = S
+                     -- nether.useBiomes allows other mods to know whether they can register ores etc. in the Nether.
+                     -- See mapgen.lua for an explanation of why minetest.read_schematic is being checked
+nether.useBiomes      = minetest.get_mapgen_setting("mg_name") ~= "v6" and minetest.read_schematic ~= nil
+nether.fogColor = {	           -- only used if climate_api is installed
+	netherCaverns = "#1D0504", -- Distance-fog colour for classic nether
+	mantle        = "#070916", -- Distance-fog colour for the Mantle region
+	geodes        = "#300530"  -- Distance-fog colour for secondary region
+}
+
 
 -- Settings
-nether.DEPTH                      = -5000 -- The y location of the Nether
-nether.FASTTRAVEL_FACTOR          =     8 -- 10 could be better value for Minetest, since there's no sprint, but ex-Minecraft players will be mathing for 8
-nether.PORTAL_BOOK_LOOT_WEIGHTING =   0.9 -- Likelyhood of finding the Book of Portals (guide) in dungeon chests. Set to 0 to disable.
-nether.NETHER_REALM_ENABLED       =  true -- Setting to false disables the Nether and Nether portal
+nether.DEPTH_CEILING              =  -5000 -- The y location of the Nether's celing
+nether.DEPTH_FLOOR                = -11000 -- The y location of the Nether's floor
+nether.FASTTRAVEL_FACTOR          =      8 -- 10 could be better value for Minetest, since there's no sprint, but ex-Minecraft players will be mathing for 8
+nether.PORTAL_BOOK_LOOT_WEIGHTING =    0.9 -- Likelyhood of finding the Book of Portals (guide) in dungeon chests. Set to 0 to disable.
+nether.NETHER_REALM_ENABLED       =   true -- Setting to false disables the Nether and Nether portal
 
 
 -- Override default settings with values from the .conf file, if any are present.
 nether.FASTTRAVEL_FACTOR          = tonumber(minetest.settings:get("nether_fasttravel_factor") or nether.FASTTRAVEL_FACTOR)
 nether.PORTAL_BOOK_LOOT_WEIGHTING = tonumber(minetest.settings:get("nether_portalBook_loot_weighting") or nether.PORTAL_BOOK_LOOT_WEIGHTING)
-nether.NETHER_REALM_ENABLED       = minetest.settings:get_bool("nether_realm_enabled", nether.NETHER_REALM_ENABLED) or nether.NETHER_REALM_ENABLED
+nether.NETHER_REALM_ENABLED       = minetest.settings:get_bool("nether_realm_enabled", nether.NETHER_REALM_ENABLED)
+nether.DEPTH_CEILING              = tonumber(minetest.settings:get("nether_depth_ymax") or nether.DEPTH_CEILING)
+nether.DEPTH_FLOOR                = tonumber(minetest.settings:get("nether_depth_ymin") or nether.DEPTH_FLOOR)
+
+if nether.DEPTH_FLOOR + 1000 > nether.DEPTH_CEILING then
+	error("The lower limit of the Nether must be set at least 1000 lower than the upper limit, and more than 3000 is recommended. Set settingtypes.txt, or 'All Settings' -> 'Mods' -> 'nether' -> 'Nether depth'", 0)
+end
+nether.DEPTH = nether.DEPTH_CEILING -- Deprecated, use nether.DEPTH_CEILING instead.
+
+-- DEPTH_FLOOR_LAYERS gives the bottom Y of all locations that wish to be
+-- considered part of the Nether.
+-- DEPTH_FLOOR_LAYERS Allows mods to insert extra layers below the
+-- Nether, by knowing where their layer ceiling should start, and letting
+-- the layers be included in effects which only happen in the Nether.
+-- If a mod wishes to add a layer below the Nether it should read
+-- nether.DEPTH_FLOOR_LAYERS to find the bottom Y of the Nether and any
+-- other layers already under the Nether. The mod should leave a small gap
+-- between DEPTH_FLOOR_LAYERS and its ceiling (e.g. use DEPTH_FLOOR_LAYERS - 6
+-- for its ceiling Y, so there is room to shift edge-case biomes), then set
+-- nether.DEPTH_FLOOR_LAYERS to reflect the mod's floor Y value, and call
+-- shift_existing_biomes() with DEPTH_FLOOR_LAYERS as the floor_y argument.
+nether.DEPTH_FLOOR_LAYERS = nether.DEPTH_FLOOR
+
+-- A debug-print function that understands vectors etc. and does not
+-- evaluate when debugging is turned off.
+-- Works like string.format(), treating the message as a format string.
+-- nils, tables, and vectors passed as arguments to nether.debug() are
+-- converted to strings and can be included inside the message with %s
+function nether.debug(message, ...)
+
+	local args = {...}
+	local argCount = select("#", ...)
+
+	for i = 1, argCount do
+		local arg = args[i]
+		if arg == nil then
+			-- convert nils to strings
+			args[i] = '<nil>'
+		elseif type(arg) == "table" then
+			local tableCount = 0
+			for _,_ in pairs(arg) do tableCount = tableCount + 1 end
+			if tableCount == 3 and arg.x ~= nil and arg.y ~= nil and arg.z ~= nil then
+				-- convert vectors to strings
+				args[i] = minetest.pos_to_string(arg)
+			else
+				-- convert tables to strings
+				-- (calling function can use dump() if a multi-line listing is desired)
+				args[i] = string.gsub(dump(arg, ""), "\n", " ")
+			end
+		end
+	end
+
+	local composed_message = "nether: " .. string.format(message, unpack(args))
+
+	if math.floor(DEBUG_FLAGS / 1) % 2 == 1 then print(composed_message) end
+	if math.floor(DEBUG_FLAGS / 2) % 2 == 1 then minetest.chat_send_all(composed_message) end
+	if math.floor(DEBUG_FLAGS / 4) % 2 == 1 then minetest.log("info", composed_message) end
+end
+if DEBUG_FLAGS == 0 then
+	-- do as little evaluation as possible
+	nether.debug = function() end
+end
 
 
 -- Load files
 dofile(nether.path .. "/portal_api.lua")
 dofile(nether.path .. "/nodes.lua")
+dofile(nether.path .. "/tools.lua")
+dofile(nether.path .. "/crafts.lua")
 if nether.NETHER_REALM_ENABLED then
-	dofile(nether.path .. "/mapgen.lua")
+	if nether.useBiomes then
+		dofile(nether.path .. "/mapgen.lua")
+	else
+		dofile(nether.path .. "/mapgen_nobiomes.lua")
+	end
 end
 dofile(nether.path .. "/portal_examples.lua")
-
+if minetest.get_modpath("technic") then
+	dofile(nether.path .. "/nether-compressor-recipe.lua")
+end
 
 -- Portals are ignited by right-clicking with a mese crystal fragment
 nether.register_portal_ignition_item(
@@ -83,15 +170,15 @@ This opens to a truly hellish place, though for small mercies the air there is s
 The expedition parties have found no diamonds or gold, and after an experienced search party failed to return from the trail of a missing expedition party, I must conclude this is a dangerous place.]], 10 * nether.FASTTRAVEL_FACTOR),
 
 		is_within_realm = function(pos) -- return true if pos is inside the Nether
-			return pos.y < nether.DEPTH
+			return pos.y < nether.DEPTH_CEILING and pos.y > nether.DEPTH_FLOOR
 		end,
 
-		find_realm_anchorPos = function(surface_anchorPos)
+		find_realm_anchorPos = function(surface_anchorPos, player_name)
 			-- divide x and z by a factor of 8 to implement Nether fast-travel
 			local destination_pos = vector.divide(surface_anchorPos, nether.FASTTRAVEL_FACTOR)
 			destination_pos.x = math.floor(0.5 + destination_pos.x) -- round to int
 			destination_pos.z = math.floor(0.5 + destination_pos.z) -- round to int
-			destination_pos.y = nether.DEPTH - 1000 -- temp value so find_nearest_working_portal() returns nether portals
+			destination_pos.y = nether.DEPTH_CEILING - 1 -- temp value so find_nearest_working_portal() returns nether portals
 
 			-- a y_factor of 0 makes the search ignore the altitude of the portals (as long as they are in the Nether)
 			local existing_portal_location, existing_portal_orientation =
@@ -100,13 +187,13 @@ The expedition parties have found no diamonds or gold, and after an experienced
 			if existing_portal_location ~= nil then
 				return existing_portal_location, existing_portal_orientation
 			else
-				local start_y = nether.DEPTH - math.random(500, 1500) -- Search starting altitude
-				destination_pos.y = nether.find_nether_ground_y(destination_pos.x, destination_pos.z, start_y)
+				local start_y = nether.DEPTH_CEILING - math.random(500, 1500) -- Search starting altitude
+				destination_pos.y = nether.find_nether_ground_y(destination_pos.x, destination_pos.z, start_y, player_name)
 				return destination_pos
 			end
 		end,
 
-		find_surface_anchorPos = function(realm_anchorPos)
+		find_surface_anchorPos = function(realm_anchorPos, player_name)
 			-- A portal definition doesn't normally need to provide a find_surface_anchorPos() function,
 			-- since find_surface_target_y() will be used by default, but Nether portals also scale position
 			-- to create fast-travel.
@@ -116,7 +203,7 @@ The expedition parties have found no diamonds or gold, and after an experienced
 			local destination_pos = vector.multiply(realm_anchorPos, nether.FASTTRAVEL_FACTOR)
 			destination_pos.x = math.min(30900, math.max(-30900, destination_pos.x)) -- clip to world boundary
 			destination_pos.z = math.min(30900, math.max(-30900, destination_pos.z)) -- clip to world boundary
-			destination_pos.y = 0 -- temp value so find_nearest_working_portal() doesn't return nether portals
+			destination_pos.y = nether.DEPTH_CEILING + 1 -- temp value so find_nearest_working_portal() doesn't return nether portals
 
 			-- a y_factor of 0 makes the search ignore the altitude of the portals (as long as they are outside the Nether)
 			local existing_portal_location, existing_portal_orientation =
@@ -125,7 +212,7 @@ The expedition parties have found no diamonds or gold, and after an experienced
 			if existing_portal_location ~= nil then
 				return existing_portal_location, existing_portal_orientation
 			else
-				destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, "nether_portal")
+				destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, "nether_portal", player_name)
 				return destination_pos
 			end
 		end,
@@ -161,4 +248,103 @@ The expedition parties have found no diamonds or gold, and after an experienced
 		end
 
 	})
-end
+
+
+	-- Set appropriate nether distance-fog if climate_api is available
+	--
+	-- Delegating to a mod like climate_api means nether won't unexpectedly stomp on the sky of
+	-- any other mod.
+	-- Skylayer is another mod which can perform this role, and skylayer support could be added
+	-- here as well. However skylayer doesn't provide a position-based method of specifying sky
+	-- colours out-of-the-box, so the nether mod will have to monitor when players enter and
+	-- leave the nether.
+	if minetest.get_modpath("climate_api") and minetest.global_exists("climate_api") and climate_api.register_weather ~= nil then
+
+		climate_api.register_influence(
+			"nether_biome",
+			function(pos)
+				local result = "surface"
+
+				if pos.y <= nether.DEPTH_CEILING and pos.y >= nether.DEPTH_FLOOR then
+					result = "nether"
+
+					-- since mapgen_nobiomes.lua has no regions it doesn't implement get_region(),
+					-- so only use get_region() if it exists
+					if nether.mapgen.get_region ~= nil then
+						-- the biomes-based mapgen supports 2 extra regions
+						local regions = nether.mapgen.RegionEnum
+						local region  = nether.mapgen.get_region(pos)
+						if region == regions.CENTER or region == regions.CENTERSHELL then
+							result = "mantle"
+						elseif region == regions.NEGATIVE or region == regions.NEGATIVESHELL then
+							result = "geode"
+						end
+					end
+				end
+
+				return result
+			end
+		)
+
+		-- using sky type "plain" unfortunately means we don't get smooth fading transitions when
+		-- the color of the sky changes, but it seems to be the only way to obtain a sky colour
+		-- which doesn't brighten during the daytime.
+		local undergroundSky = {
+			sky_data = {
+				base_color = nil,
+				type = "plain",
+				textures = nil,
+				clouds = false,
+			},
+			sun_data = {
+				visible = false,
+				sunrise_visible = false
+			},
+			moon_data = {
+				visible = false
+			},
+			star_data = {
+				visible = false
+			}
+		}
+
+		local netherSky, mantleSky, geodeSky = table.copy(undergroundSky), table.copy(undergroundSky), table.copy(undergroundSky)
+		netherSky.sky_data.base_color = nether.fogColor.netherCaverns
+		mantleSky.sky_data.base_color = nether.fogColor.mantle
+		geodeSky.sky_data.base_color  = nether.fogColor.geodes
+
+		climate_api.register_weather(
+			"nether:caverns",
+			{ nether_biome = "nether" },
+			{ ["climate_api:skybox"] = netherSky }
+		)
+
+		climate_api.register_weather(
+			"nether:mantle",
+			{ nether_biome = "mantle" },
+			{ ["climate_api:skybox"] = mantleSky }
+		)
+
+		climate_api.register_weather(
+			"nether:geode",
+			{ nether_biome = "geode" },
+			{ ["climate_api:skybox"] = geodeSky }
+		)
+	end
+
+end -- end of "if nether.NETHER_REALM_ENABLED..."
+
+
+-- Play bubbling lava sounds if player killed by lava
+minetest.register_on_dieplayer(
+	function(player, reason)
+		if reason.node ~= nil and minetest.get_node_group(reason.node, "lava") > 0 or reason.node == "nether:lava_crust" then
+			minetest.sound_play(
+				"nether_lava_bubble",
+				-- this sample was encoded at 3x speed to reduce .ogg file size
+				-- at the expense of higher frequencies, so pitch it down ~3x
+				{to_player = player:get_player_name(), pitch = 0.3, gain = 0.8}
+			)
+		end
+	end
+)

locale/nether.fr.tr

@@ -0,0 +1,141 @@
+# textdomain: nether
+
+# Translation FR by Louis Royer and JoeEnderman
+
+
+### init.lua ###
+
+Construction requires 14 blocks of obsidian, which we found deep underground where water had solidified molten rock. The finished frame is four blocks wide, five blocks high, and stands vertically, like a doorway.@n@nThis opens to a truly hellish place, though for small mercies the air there is still breathable. There is an intriguing dimensional mismatch happening between this realm and ours, as after opening the second portal into it we observed that 10 strides taken in the Nether appear to be an equivalent of @1 in the natural world.@n@nThe expedition parties have found no diamonds or gold, and after an experienced search party failed to return from the trail of a missing expedition party, I must conclude this is a dangerous place.=Cette construction nécessite 14 blocs d’obsidienne, qui peut être trouvée profondément sous terre, là où l’eau a solidifié de la roche fondue. Une fois terminé, le cadre fait quatre blocs de large, cinq blocs de haut, et se tient verticalement comme une porte.@n@nElle ouvre sur un lieu vraiment infernal, mais on peut s’estimer heureux que l’air y soit quand même respirable. Il y a un décalage dimensionnel intrigant entre ce monde et le nôtre, car après avoir ouvert un deuxième portail, nous avons observé que 10 pas effectués dans le Nether semblent être l’équivalent de @1 dans notre monde.@n@nLes membres de l’expédition n’ontr trouvé ni diamants ni or, et après qu’un groupe de recheche expérimenté n’ait pas réussi à retrouver la piste d’un membre de l’expédition disparu, je n’ai d’autre choix que de conclure que cet endroit est trop dangereux pour nous.
+
+
+### init.lua ###
+### nodes.lua ###
+
+Nether Portal=Portail du Nether
+
+### mapgen_mantle.lua ###
+
+, @1m above lava-sea level=, @1m au-dessus du niveau de la mer de lave
+, @1m below lava-sea level=, @1m en-dessous du niveau de la mer de lave
+, approaching y boundary of Nether=, approchant de la limite y du Nether
+@1@2@3@4=
+Center/Mantle, but outside the caverns=Centre/Manteau, mais à l'extérieur des cavernes
+Center/Mantle, inside cavern=Centre/Manteau, à l'intérieur d'une caverne
+Describes which region of the nether the player is in=Indique dans quelle région du Nether se trouve le joueur
+Negative nether=Nether négatif
+Positive nether=Nether positif
+Shell between negative nether and center region=Coquille entre le Nether négatif et la région centrale
+Shell between positive nether and center region=Coquille entre le Nether positif et la région centrale
+The Overworld=L'Overworld
+Unknown player position=Position du joueur inconnue
+[Perlin @1] =
+
+### nodes.lua ###
+
+A Deep Netherrack Wall=Un mur profond en Netherrack
+A Netherrack Wall=Un mur en Netherrack
+A finely finished block of solid Nether Basalt.=Un bloc fini de basalte du Nether solide.
+A rough cut solid block of Nether Basalt.=Un bloc solide de basalte du Nether taillé à la hache.
+A thin crust of cooled lava with liquid lava beneath=Une croûte fine de lave refroidie avec de la lave liquide en dessous
+A vent in the earth emitting steam and gas=Une fissure dans la terre émettant de la vapeur et du gaz
+Can be repurposed to provide puffs of smoke in a chimney=Peut être réutilisé pour produire des bouffées de fumée dans une cheminée
+Chiselled Basalt=Basalte sculpté
+
+Columns of dark basalt found only in magma oceans deep within the Nether.=Colonnes de basalte noir que l'on trouve uniquement dans les océans de magma profonds du Nether.
+
+Compressed Netherbrick=Briques du Nether compressées
+Cracked Nether Brick=Briques du Nether craquelées
+Deep Glowstone=Pierre lumineuse profonde
+Deep Nether Brick=Briques du Nether profondes
+Deep Nether Slab=Dalle du Nether profonde
+Deep Nether Stair=Escalier du Nether profond
+Deep Netherrack=Netherrack profond
+Deep Netherrack Slab=Dalle de Netherrack profonde
+Deep Netherrack Stair=Escalier de Netherrack profond
+Fumarolic Chimney=Cheminée fumarolique
+Fumarolic Chimney Corner=Coin de cheminée fumarolique
+Fumarolic Chimney Slab=Dalle de cheminée fumarolique
+Glowstone=Pierre lumineuse
+Hewn Basalt=Basalte taillé
+Inner Deep Nether Stair=Escalier intérieur du Nether profond
+Inner Nether Stair=Escalier intérieur du Nether
+Lava Crust=Croûte de lave
+
+Lava crust is strong enough to walk on, but still hot enough to inflict burns.=La croûte de lave est assez solide pour marcher dessus, mais encore assez chaude pour causer des brûlures
+
+Nether Basalt=Basalte du Nether
+Nether Beryl=Béryl du Nether
+Nether Berylite=Bérylite du Nether
+Nether Brick=Brique du Nether
+Nether Brick Fence=Barrière en briques du Nether
+Nether Brick Fence Rail=Rail de barrière en briques du Nether
+Nether Crystal Pane=Panneau de cristal du Nether
+Nether Slab=Dalle du Nether
+Nether Stair=Escalier du Nether
+
+Nether geode crystal, found lining the interior walls of Nether geodes=Cristal de géode du Nether, trouvé le long des parois intérieures des géodes du Nether
+
+Nether geode crystal. A crystalline structure with faint glow found inside large Nether geodes=Cristal de géode du Nether. Une structure cristalline avec une faible lueur trouvée à l'intérieur des grandes géodes du Nether.
+
+Netherrack=Roche du Nether
+Netherrack from deep in the mantle=Roche du Nether provenant des profondeurs du manteau
+Netherrack Slab=Dalle du Nether
+Netherrack Stair=Escalier du Nether
+Nethersand=Sable du Nether
+Outer Deep Nether Stair=Escalier extérieur profond du Nether
+Outer Nether Stair=Escalier extérieur du Nether
+Portal=Portail
+
+### portal_api.lua ###
+
+@n@nThe key to opening such a doorway is to strike the frame with a @1, at which point the very air inside begins to crackle and glow.=@n@nLa méthode pour ouvrir une telle porte est de frapper son cadre avec un @1, jusqu’à ce que tout l’air à l’intérieur commence à crépiter et briller.
+
+A definitive guide to Rifts and Portals=Un guide détaillé des failles et des portails
+
+A guidebook for how to build portals to other realms. It can sometimes be found in dungeon chests, however a copy of this book is not needed as its contents are included in this Encyclopedia.=Un guide sur comment construire des portails vers d’autres mondes. Il peut parfois être trouvé dans des coffres de dongeons, cependant la copie de ce livre n’est pas nécessaire puisque son contenu est inclus dans l’encyclopédie.
+
+Book of Portals=Livre des portails
+Building Portals=Construire des portails
+
+In all my travels, and time spent in the Great Libraries, I have encountered no shortage of legends surrounding preternatural doorways said to open into other worlds, yet only @1 can I confirm as being more than merely stories.=Après tous mes voyages, et le temps passé dans les Grandes Bibliothèques, je ne manque pas de légendes sur les portes surnaturelles qui, dit-on s’ouvrent vers d’autres mondes, mais seul @1 peut confirmer que ce sont plus que de simples histoires.
+
+In all my travels, and time spent in the Great Libraries, I have encountered no shortage of legends surrounding preternatural doorways said to open into other worlds, yet only one can I confirm as being more than merely a story.=Après tous mes voyages, et le temps passé dans les Grandes Bibliothèques, je ne manque pas de légendes sur les portes surnaturelles qui, dit-on s’ouvrent vers d’autres mondes, mais seul une personne peut confirmer que ce sont plus que de simples histoires.
+
+Mysterious forces prevented you from opening that portal. Please try another location=Des forces mystérieuses vous empêchent d'ouvrir ce portail. Veuillez essayer un autre emplacement.
+
+Portal wormhole=Vortex du portail
+
+Portals to other realms can be opened by building a frame in the right shape with the right blocks, then using an item to activate it. A local copy of the guidebook to portals is published below.@n---@n@n=Les portails vers d’autres mondes peuvent être ouvert en construisant un cadre de la bonne forme avec les bons blocs, puis en utilisant un objet pour l’activer. Une copie du guide des portails est ci-dessous.@n---@n@n
+
+Refer: "Help" > "Basics" > "Building Portals"=Voir : Aide > Bases > Construire des portails
+Untitled portal=Portail sans nom
+We know almost nothing about this portal=Nous ne savons presque rien sur les portails
+
+### portal_examples.lua ###
+
+Floatlands Portal=Portail du monde flottant
+
+Requiring 16 blocks of tin and constructed in a circular fashion, a finished frame is seven blocks wide, seven blocks high, and stands vertically like a doorway.@n@nThese travel a distance along the ground, and even when constructed deep underground will link back up to the surface. They appear to favor a strange direction, with the exit portal linking back only for as long as the portal stays open — attempting to reopen a portal from the exit doorway leads to a new destination along this favored direction. It has stymied our ability to study the behavior of these portals because without constructing dual portals and keeping both open it's hard to step through more than one and still be able to return home.@n@nDue to such difficulties, we never learned what determines the direction and distance where the matching twin portal will appear, and I have lost my friend and protégé. In cavalier youth and with little more than a rucksack, Coudreau has decided to follow the chain as far as it goes, and has not been seen since. Coudreau believes it works in epicycles, but I am not convinced. Still, I cling to the hope that one day the portal will open and Coudreau will step out from whichever place leads to this one, perhaps with an epic tale to tell.=Nécessite 16 blocs d’étain placés de manière circulaire, le cadre final fait sept blocs de large, sept blocs de haut, et se tient verticalement comme une porte.@n@nIls permettent de voyager une distance sous le sol et se relieent à la surface même s’ils sont construits profondément sous terre. Ils ont l’air de préférer une direction étrange, avec le portail de sortie ne se reliant au portail d’entrée que tant qu’ils restent tous deux ouverts – tenter de réouvrir le portail de sortie mènera à une nouvelle destination dans cette direction privilégiée.Cela a entravé notre capacité à étudier le comportement de ces portails, car sans la construction de doubles portails et en gardant les deux ouverts, il est difficile d'en traverser plus d'un et de pouvoir rentrer chez soi.@n@nEn raison de ces difficultés, nous n'avons jamais appris ce qui détermine la direction et la distance à laquelle le portail jumeau correspondant apparaîtra, et j’ai perdu mon ami et mon protégé. Dans sa jeunesse cavalière et avec à peine plus qu'un sac à dos, Coudreau a décidé de suivre la chaîne jusqu'au bout, et n'a pas été vu depuis. Coudreau croit qu'elle fonctionne sur les épicycles, mais je n'en suis pas convaincu. Je m'accroche néanmoins à l'espoir qu'un jour le portail s'ouvrira et que Coudreau sortira de l'endroit qui mène à celui-ci, peut-être avec un récit épique à raconter.
+
+Requiring 21 blocks of ice, and constructed in the shape of a 3 × 3 platform with walls, or like a bowl. A finished platform is 2 blocks high, and 5 blocks wide at the widest in both directions.@n@nThis portal is different to the others, rather than acting akin to a doorway it appears to the eye more like a small pool of water which can be stepped into. Upon setting foot in the portal we found ourselves at a tremendous altitude.@1=Nécessite 21 blocs de glace placés pour former une plateforme de 3 × 3 avec des murs, ou comme un bol. La plateforme finale fait 2 blocs de haut, et 5 blocs de large à sa largeur maximale dans les deux directions.@n@nCe portail est différent des autres, au lieu de ressembler à une porte, il ressemble plus à un petit bassin d’eau dans lequel on peut entrer. En mettant les pieds dans le portail, nous nous sommes retrouvés à une altitude énorme.@1
+
+Surface Portal=Portail de surface
+
+There is a floating land of hills and forests up there, over the edges of which is a perilous drop all the way back down to sea level. We have not found how far these pristine lands extend. I have half a mind to retire there one day.=Il y a là un monde flottant remplis de collines et de forêts, sur les bords duquel se trouve une chute périlleuse jusqu'au niveau de la mer. Nous n'avons pas encore trouvé jusqu'où s'étendent ces terres vierges. J'ai à moitié envie de m'y retirer un jour.
+
+
+### tools.lua ###
+
+Nether Axe=Hache du Nether
+Nether Ingot=Lingot du Nether
+Nether Lump=Morceau du Nether
+Nether Pickaxe@nWell suited for mining netherrack=Pioche du Nether@nBien adaptée pour miner la roche du Nether
+Nether Shovel=Pelle du Nether
+Nether Sword=Épée du Nether
+
+Nether staff of Eternal Light@nCreates glowstone from netherrack=Bâton du Nether de lumière éternelle@nCrée des blocs de pierre lumineuse à partir de roche du Nether
+
+Nether staff of Light@nTemporarily transforms the netherrack into glowstone=Bâton du Nether de lumière@nTransforme temporairement la roche du Nether en blocs de pierre lumineuse
+
+Uniquely suited for mining netherrack, with minimal wear when doing so. Blunts quickly on other materials.=Convient parfaitement pour miner la roche du Nether avec une usure minimale. S'émousse rapidement sur les autres matériaux.
+

locale/template.txt

@@ -0,0 +1,140 @@
+# textdomain: nether
+
+
+
+### init.lua ###
+
+Construction requires 14 blocks of obsidian, which we found deep underground where water had solidified molten rock. The finished frame is four blocks wide, five blocks high, and stands vertically, like a doorway.@n@nThis opens to a truly hellish place, though for small mercies the air there is still breathable. There is an intriguing dimensional mismatch happening between this realm and ours, as after opening the second portal into it we observed that 10 strides taken in the Nether appear to be an equivalent of @1 in the natural world.@n@nThe expedition parties have found no diamonds or gold, and after an experienced search party failed to return from the trail of a missing expedition party, I must conclude this is a dangerous place.=
+
+
+### init.lua ###
+### nodes.lua ###
+
+Nether Portal=
+
+### mapgen_mantle.lua ###
+
+, @1m above lava-sea level=
+, @1m below lava-sea level=
+, approaching y boundary of Nether=
+@1@2@3@4=
+Center/Mantle, but outside the caverns=
+Center/Mantle, inside cavern=
+Describes which region of the nether the player is in=
+Negative nether=
+Positive nether=
+Shell between negative nether and center region=
+Shell between positive nether and center region=
+The Overworld=
+Unknown player position=
+[Perlin @1] =
+
+### nodes.lua ###
+
+A Deep Netherrack Wall=
+A Netherrack Wall=
+A finely finished block of solid Nether Basalt.=
+A rough cut solid block of Nether Basalt.=
+A thin crust of cooled lava with liquid lava beneath=
+A vent in the earth emitting steam and gas=
+Can be repurposed to provide puffs of smoke in a chimney=
+Chiselled Basalt=
+
+Columns of dark basalt found only in magma oceans deep within the Nether.=
+
+Compressed Netherbrick=
+Cracked Nether Brick=
+Deep Glowstone=
+Deep Nether Brick=
+Deep Nether Slab=
+Deep Nether Stair=
+Deep Netherrack=
+Deep Netherrack Slab=
+Deep Netherrack Stair=
+Fumarolic Chimney=
+Fumarolic Chimney Corner=
+Fumarolic Chimney Slab=
+Glowstone=
+Hewn Basalt=
+Inner Deep Nether Stair=
+Inner Nether Stair=
+Lava Crust=
+
+Lava crust is strong enough to walk on, but still hot enough to inflict burns.=
+
+Nether Basalt=
+Nether Beryl=
+Nether Berylite=
+Nether Brick=
+Nether Brick Fence=
+Nether Brick Fence Rail=
+Nether Crystal Pane=
+Nether Slab=
+Nether Stair=
+
+Nether geode crystal, found lining the interior walls of Nether geodes=
+
+Nether geode crystal. A crystalline structure with faint glow found inside large Nether geodes=
+
+Netherrack=
+Netherrack from deep in the mantle=
+Netherrack Slab=
+Netherrack Stair=
+Nethersand=
+Outer Deep Nether Stair=
+Outer Nether Stair=
+Portal=
+
+### portal_api.lua ###
+
+@n@nThe key to opening such a doorway is to strike the frame with a @1, at which point the very air inside begins to crackle and glow.=
+
+A definitive guide to Rifts and Portals=
+
+A guidebook for how to build portals to other realms. It can sometimes be found in dungeon chests, however a copy of this book is not needed as its contents are included in this Encyclopedia.=
+
+Book of Portals=
+Building Portals=
+
+In all my travels, and time spent in the Great Libraries, I have encountered no shortage of legends surrounding preternatural doorways said to open into other worlds, yet only @1 can I confirm as being more than merely stories.=
+
+In all my travels, and time spent in the Great Libraries, I have encountered no shortage of legends surrounding preternatural doorways said to open into other worlds, yet only one can I confirm as being more than merely a story.=
+
+Mysterious forces prevented you from opening that portal. Please try another location=
+
+Portal wormhole=
+
+Portals to other realms can be opened by building a frame in the right shape with the right blocks, then using an item to activate it. A local copy of the guidebook to portals is published below.@n---@n@n=
+
+Refer: "Help" > "Basics" > "Building Portals"=
+Untitled portal=
+We know almost nothing about this portal=
+
+### portal_examples.lua ###
+
+Floatlands Portal=
+
+Requiring 16 blocks of tin and constructed in a circular fashion, a finished frame is seven blocks wide, seven blocks high, and stands vertically like a doorway.@n@nThese travel a distance along the ground, and even when constructed deep underground will link back up to the surface. They appear to favor a strange direction, with the exit portal linking back only for as long as the portal stays open — attempting to reopen a portal from the exit doorway leads to a new destination along this favored direction. It has stymied our ability to study the behavior of these portals because without constructing dual portals and keeping both open it's hard to step through more than one and still be able to return home.@n@nDue to such difficulties, we never learned what determines the direction and distance where the matching twin portal will appear, and I have lost my friend and protégé. In cavalier youth and with little more than a rucksack, Coudreau has decided to follow the chain as far as it goes, and has not been seen since. Coudreau believes it works in epicycles, but I am not convinced. Still, I cling to the hope that one day the portal will open and Coudreau will step out from whichever place leads to this one, perhaps with an epic tale to tell.=
+
+Requiring 21 blocks of ice, and constructed in the shape of a 3 × 3 platform with walls, or like a bowl. A finished platform is 2 blocks high, and 5 blocks wide at the widest in both directions.@n@nThis portal is different to the others, rather than acting akin to a doorway it appears to the eye more like a small pool of water which can be stepped into. Upon setting foot in the portal we found ourselves at a tremendous altitude.@1=
+
+Surface Portal=
+
+There is a floating land of hills and forests up there, over the edges of which is a perilous drop all the way back down to sea level. We have not found how far these pristine lands extend. I have half a mind to retire there one day.=
+
+
+### tools.lua ###
+
+Nether Axe=
+Nether Ingot=
+Nether Lump=
+Nether Pickaxe@nWell suited for mining netherrack=
+Nether Shovel=
+Nether Sword=
+
+Nether staff of Eternal Light@nCreates glowstone from netherrack=
+
+Nether staff of Light@nTemporarily transforms the netherrack into glowstone=
+
+Uniquely suited for mining netherrack, with minimal wear when doing so. Blunts quickly on other materials.=
+

mapgen.lua

@@ -2,6 +2,12 @@
 
   Nether mod for minetest
 
+  "mapgen.lua" is the modern biomes-based Nether mapgen, which
+    requires Minetest v5.1 or greater
+  "mapgen_nobiomes.lua" is the legacy version of the mapgen, only used
+    in older versions of Minetest or in v6 worlds.
+
+
   Copyright (C) 2013 PilzAdam
 
   Permission to use, copy, modify, and/or distribute this software for
@@ -22,14 +28,231 @@
 
 -- Parameters
 
-local NETHER_DEPTH = nether.DEPTH
+local NETHER_CEILING = nether.DEPTH_CEILING
+local NETHER_FLOOR   = nether.DEPTH_FLOOR
 local TCAVE = 0.6
 local BLEND = 128
 
+-- parameters for central region
+local REGION_BUFFER_THICKNESS   = 0.2
+local CENTER_REGION_LIMIT       = TCAVE - REGION_BUFFER_THICKNESS -- Netherrack gives way to Deep-Netherrack here
+local CENTER_CAVERN_LIMIT       = CENTER_REGION_LIMIT - 0.1       -- Deep-Netherrack gives way to air here
+local SURFACE_CRUST_LIMIT       = CENTER_CAVERN_LIMIT * 0.25      -- Crusted-lava at the surface of the lava ocean gives way to liquid lava here
+local CRUST_LIMIT               = CENTER_CAVERN_LIMIT * 0.85      -- Crusted-lava under the surface of the lava ocean gives way to liquid lava here
+local BASALT_COLUMN_UPPER_LIMIT = CENTER_CAVERN_LIMIT * 0.9       -- Basalt columns may appear between these upper and lower limits
+local BASALT_COLUMN_LOWER_LIMIT = CENTER_CAVERN_LIMIT * 0.25      -- This value is close to SURFACE_CRUST_LIMIT so basalt columns give way to "flowing" lava rivers
+
+
+-- Shared Nether mapgen namespace
+-- For mapgen files to share functions and constants
+local mapgen = nether.mapgen
+
+mapgen.TCAVE                     = TCAVE                     -- const needed in mapgen_mantle.lua
+mapgen.BLEND                     = BLEND                     -- const needed in mapgen_mantle.lua
+mapgen.CENTER_REGION_LIMIT       = CENTER_REGION_LIMIT       -- const needed in mapgen_mantle.lua
+mapgen.CENTER_CAVERN_LIMIT       = CENTER_CAVERN_LIMIT       -- const needed in mapgen_mantle.lua
+mapgen.BASALT_COLUMN_UPPER_LIMIT = BASALT_COLUMN_UPPER_LIMIT -- const needed in mapgen_mantle.lua
+mapgen.BASALT_COLUMN_LOWER_LIMIT = BASALT_COLUMN_LOWER_LIMIT -- const needed in mapgen_mantle.lua
+
+mapgen.ore_ceiling = NETHER_CEILING - BLEND -- leave a solid 128 node cap of netherrack before introducing ores
+mapgen.ore_floor   = NETHER_FLOOR   + BLEND
+
+local debugf = nether.debug
+
+if minetest.read_schematic == nil then
+	-- Using biomes to create the Nether requires the ability for biomes to set "node_cave_liquid = air".
+	-- This feature was introduced by paramat in b1b40fef1 on 2019-05-19, but we can't test for
+	-- it directly. However b2065756c was merged a few months later (in 2019-08-14) and it is easy
+	-- to directly test for - it adds minetest.read_schematic() - so we use this as a proxy-test
+	-- for whether the Minetest engine is recent enough to have implemented node_cave_liquid=air
+	error("This " .. nether.modname .. " mapgen requires Minetest v5.1 or greater, use mapgen_nobiomes.lua instead.", 0)
+end
+
+-- Load specialty helper functions
+dofile(nether.path .. "/mapgen_dungeons.lua")
+dofile(nether.path .. "/mapgen_mantle.lua")
+dofile(nether.path .. "/mapgen_geodes.lua")
+
+
+-- Misc math functions
+
+-- avoid needing table lookups each time a common math function is invoked
+local math_max, math_min, math_abs, math_floor = math.max, math.min, math.abs, math.floor
+
+
+-- Inject nether_caverns biome
+
+-- Move any existing biomes out of the y-range specified by 'floor_y' and 'ceiling_y'
+mapgen.shift_existing_biomes = function(floor_y, ceiling_y)
+	-- https://forum.minetest.net/viewtopic.php?p=257522#p257522
+	-- Q: Is there a way to override an already-registered biome so I can get it out of the
+	--    way of my own underground biomes without disturbing the other biomes registered by
+	--    default?
+	-- A: No, all you can do is use a mod to clear all biomes then re-register the complete
+	--    set but with your changes. It has been described as hacky but this is actually the
+	--    official way to alter biomes, most mods and subgames would want to completely change
+	--    all biomes anyway.
+	--    To avoid the engine side of mapgen becoming overcomplex the approach is to require mods
+	--    to do slightly more complex stuff in Lua.
+
+	-- take a copy of all biomes, decorations, and ores. Regregistering a biome changes its ID, so
+	-- any decorations or ores using the 'biomes' field must afterwards be cleared and re-registered.
+	-- https://github.com/minetest/minetest/issues/9288
+	local registered_biomes_copy      = {}
+	local registered_decorations_copy = {}
+	local registered_ores_copy        = {}
+
+	for old_biome_key, old_biome_def in pairs(minetest.registered_biomes) do
+	   registered_biomes_copy[old_biome_key] = old_biome_def
+	end
+	for old_decoration_key, old_decoration_def in pairs(minetest.registered_decorations) do
+	   registered_decorations_copy[old_decoration_key] = old_decoration_def
+	end
+	for old_ore_key, old_ore_def in pairs(minetest.registered_ores) do
+		registered_ores_copy[old_ore_key] = old_ore_def
+	end
+
+	-- clear biomes, decorations, and ores
+	minetest.clear_registered_decorations()
+	minetest.clear_registered_ores()
+	minetest.clear_registered_biomes()
+
+	-- Restore biomes, adjusted to not overlap the Nether
+	for biome_key, new_biome_def in pairs(registered_biomes_copy) do
+		-- follow similar min_pos/max_pos processing logic as read_biome_def() in l_mapgen.cpp
+		local biome_y_max, biome_y_min = 31000, -31000
+		if type(new_biome_def.min_pos) == 'table' and type(new_biome_def.min_pos.y) == 'number' then biome_y_min = new_biome_def.min_pos.y end
+		if type(new_biome_def.max_pos) == 'table' and type(new_biome_def.max_pos.y) == 'number' then biome_y_max = new_biome_def.max_pos.y end
+		if type(new_biome_def.y_min) == 'number' then biome_y_min = new_biome_def.y_min end
+		if type(new_biome_def.y_max) == 'number' then biome_y_max = new_biome_def.y_max end
+
+		if biome_y_max > floor_y and biome_y_min < ceiling_y then
+			-- This biome occupies some or all of the depth of the Nether, shift/crop it.
+			local new_y_min, new_y_max
+			local spaceOccupiedAbove = biome_y_max - ceiling_y
+			local spaceOccupiedBelow = floor_y - biome_y_min
+			if spaceOccupiedAbove >= spaceOccupiedBelow or biome_y_min <= -30000 then
+				-- place the biome above the Nether
+				-- We also shift biomes which extend to the bottom of the map above the Nether, since they
+				-- likely only extend that deep as a catch-all, and probably have a role nearer the surface.
+				new_y_min = ceiling_y + 1
+				new_y_max = math_max(biome_y_max, ceiling_y + 2)
+			else
+				-- shift the biome to below the Nether
+				new_y_max = floor_y - 1
+				new_y_min = math_min(biome_y_min, floor_y - 2)
+			end
+
+			debugf("Moving biome \"%s\" from %s..%s to %s..%s", new_biome_def.name, new_biome_def.y_min, new_biome_def.y_max, new_y_min, new_y_max)
+
+			if type(new_biome_def.min_pos) == 'table' and type(new_biome_def.min_pos.y) == 'number' then new_biome_def.min_pos.y = new_y_min end
+			if type(new_biome_def.max_pos) == 'table' and type(new_biome_def.max_pos.y) == 'number' then new_biome_def.max_pos.y = new_y_max end
+			new_biome_def.y_min = new_y_min -- Ensure the new heights are saved, even if original biome never specified one
+			new_biome_def.y_max = new_y_max
+		end
+		minetest.register_biome(new_biome_def)
+	end
+
+	-- Restore biome decorations
+	for decoration_key, new_decoration_def in pairs(registered_decorations_copy) do
+	   minetest.register_decoration(new_decoration_def)
+	end
+	-- Restore biome ores
+	for ore_key, new_ore_def in pairs(registered_ores_copy) do
+		minetest.register_ore(new_ore_def)
+	 end
+ end
+
+-- Shift any overlapping biomes out of the way before we create the Nether biomes
+mapgen.shift_existing_biomes(NETHER_FLOOR, NETHER_CEILING)
+
+-- nether:native_mapgen is used to prevent ores and decorations being generated according
+-- to landforms created by the native mapgen.
+-- Ores and decorations can be registered against "nether:rack" instead, and the lua
+-- on_generate() callback will carve the Nether with nether:rack before invoking
+-- generate_decorations and generate_ores.
+-- It is disguised as stone to hide any bug where it leaks out of the nether, such as
+-- https://github.com/minetest/minetest/issues/13440 or if on_generated() somehow was aborted.
+local stone_copy_def = table.copy(minetest.registered_nodes["default:stone"] or {})
+stone_copy_def.drop = stone_copy_def.drop or "default:stone" -- probably already defined as cobblestone
+minetest.register_node("nether:native_mapgen", stone_copy_def)
+
+minetest.register_biome({
+	name = "nether_caverns",
+	node_stone  = "nether:native_mapgen", -- nether:native_mapgen is used here to prevent the native mapgen from placing ores and decorations.
+	node_filler = "nether:native_mapgen", -- The lua on_generate will transform nether:native_mapgen into nether:rack then decorate and add ores.
+	node_dungeon = "nether:brick",
+	node_dungeon_alt = "nether:brick_cracked",
+	node_dungeon_stair = "stairs:stair_nether_brick",
+	-- Setting node_cave_liquid to "air" avoids the need to filter lava and water out of the mapchunk and
+	-- surrounding shell (overdraw nodes beyond the mapchunk).
+	-- This feature was introduced by paramat in b1b40fef1 on 2019-05-19, and this mapgen.lua file should only
+	-- be run if the Minetest version includes it. The earliest tag made after 2019-05-19 is 5.1.0 on 2019-10-13,
+	-- however we shouldn't test version numbers. minetest.read_schematic() was added by b2065756c and merged in
+	-- 2019-08-14 and is easy to test for, we don't use it but it should make a good proxy-test for whether the
+	-- Minetest version is recent enough to have implemented node_cave_liquid=air
+	node_cave_liquid = "air",
+	y_max = NETHER_CEILING,
+	y_min = NETHER_FLOOR,
+	vertical_blend = 0,
+	heat_point = 50,
+	humidity_point = 50,
+})
+
+
+-- Ores and decorations
+
+dofile(nether.path .. "/mapgen_decorations.lua")
+
+minetest.register_ore({
+	ore_type       = "scatter",
+	ore            = "nether:glowstone",
+	wherein        = "nether:rack",
+	clust_scarcity = 11 * 11 * 11,
+	clust_num_ores = 3,
+	clust_size     = 2,
+	y_max = mapgen.ore_ceiling,
+	y_min = mapgen.ore_floor
+})
+
+minetest.register_ore({
+	ore_type       = "scatter",
+	ore            = "nether:lava_crust", -- crusted lava replaces scattered glowstone in the mantle
+	wherein        = "nether:rack_deep",
+	clust_scarcity = 16 * 16 * 16,
+	clust_num_ores = 4,
+	clust_size     = 2,
+	y_max = mapgen.ore_ceiling,
+	y_min = mapgen.ore_floor
+})
+
+minetest.register_ore({
+	ore_type       = "scatter",
+	ore            = "default:lava_source",
+	wherein        = {"nether:rack", "nether:rack_deep"},
+	clust_scarcity = 36 * 36 * 36,
+	clust_num_ores = 4,
+	clust_size     = 2,
+	y_max = mapgen.ore_ceiling,
+	y_min = mapgen.ore_floor
+})
+
+minetest.register_ore({
+	ore_type        = "blob",
+	ore             = "nether:sand",
+	wherein         = "nether:rack",
+	clust_scarcity  = 14 * 14 * 14,
+	clust_size      = 8,
+	y_max = mapgen.ore_ceiling,
+	y_min = mapgen.ore_floor
+})
+
+
+-- Mapgen
 
 -- 3D noise
 
-local np_cave = {
+mapgen.np_cave = {
 	offset = 0,
 	scale = 1,
 	spread = {x = 384, y = 128, z = 384}, -- squashed 3:1
@@ -40,180 +263,253 @@ local np_cave = {
 	--flags = ""
 }
 
+local cavePointPerlin = nil
 
--- Stuff
+mapgen.get_cave_point_perlin = function()
+	cavePointPerlin = cavePointPerlin or minetest.get_perlin(mapgen.np_cave)
+	return cavePointPerlin
+end
 
-local yblmax = NETHER_DEPTH - BLEND * 2
+mapgen.get_cave_perlin_at = function(pos)
+	cavePointPerlin = cavePointPerlin or minetest.get_perlin(mapgen.np_cave)
+	return cavePointPerlin:get_3d(pos)
+end
 
 
-
-
--- Mapgen
-
--- Initialize noise object, localise noise and data buffers
+-- Buffers and objects we shouldn't recreate every on_generate
 
 local nobj_cave = nil
-local nbuf_cave = nil
-local dbuf = nil
+local nbuf_cave = {}
+local dbuf = {}
 
 
 -- Content ids
 
-local c_air = minetest.get_content_id("air")
+local c_air              = minetest.get_content_id("air")
+local c_netherrack       = minetest.get_content_id("nether:rack")
+local c_netherrack_deep  = minetest.get_content_id("nether:rack_deep")
+local c_crystaldark      = minetest.get_content_id("nether:geode")
+local c_lavasea_source   = minetest.get_content_id("nether:lava_source") -- same as lava but with staggered animation to look better as an ocean
+local c_lava_crust       = minetest.get_content_id("nether:lava_crust")
+local c_native_mapgen    = minetest.get_content_id("nether:native_mapgen")
 
---local c_stone_with_coal = minetest.get_content_id("default:stone_with_coal")
---local c_stone_with_iron = minetest.get_content_id("default:stone_with_iron")
-local c_stone_with_mese = minetest.get_content_id("default:stone_with_mese")
-local c_stone_with_diamond = minetest.get_content_id("default:stone_with_diamond")
-local c_stone_with_gold = minetest.get_content_id("default:stone_with_gold")
---local c_stone_with_copper = minetest.get_content_id("default:stone_with_copper")
-local c_mese = minetest.get_content_id("default:mese")
 
-local c_gravel = minetest.get_content_id("default:gravel")
-local c_dirt = minetest.get_content_id("default:dirt")
-local c_sand = minetest.get_content_id("default:sand")
 
-local c_cobble = minetest.get_content_id("default:cobble")
-local c_mossycobble = minetest.get_content_id("default:mossycobble")
-local c_stair_cobble = minetest.get_content_id("stairs:stair_cobble")
+local yblmin = NETHER_FLOOR   + BLEND * 2
+local yblmax = NETHER_CEILING - BLEND * 2
+-- At both the top and bottom of the Nether, as set by NETHER_CEILING and NETHER_FLOOR,
+-- there is a 128 deep cap of solid netherrack, followed by a 128-deep blending zone
+-- where Nether caverns may start to appear.
+-- The solid zones and blending zones are achieved by adjusting the np_cave noise to be
+-- outside the range where caverns form, this function returns that adjustment.
+--
+-- Returns two values: the noise limit adjustment for nether caverns, and the
+-- noise limit adjustment for the central region / mantle caverns
+mapgen.get_mapgenblend_adjustments = function(y)
 
-local c_lava_source = minetest.get_content_id("default:lava_source")
-local c_lava_flowing = minetest.get_content_id("default:lava_flowing")
-local c_water_source = minetest.get_content_id("default:water_source")
-local c_water_flowing = minetest.get_content_id("default:water_flowing")
+	-- floorAndCeilingBlend will normally be 0, but shifts toward 1 in the
+	-- blending zone, and goes higher than 1 in the solid zone between the
+	-- blending zone and the end of the nether.
+	local floorAndCeilingBlend = 0
+	if y > yblmax then floorAndCeilingBlend = ((y - yblmax) / BLEND) ^ 2 end
+	if y < yblmin then floorAndCeilingBlend = ((yblmin - y) / BLEND) ^ 2 end
+
+	-- the nether caverns exist when np_cave noise is greater than TCAVE, so
+	-- to fade out the nether caverns, adjust TCAVE upward.
+	local tcave_adj               = floorAndCeilingBlend
+
+	-- the central regions exists when np_cave noise is below CENTER_REGION_LIMIT,
+	-- so to fade out the mantle caverns adjust CENTER_REGION_LIMIT downward.
+	local centerRegionLimit_adj = -(CENTER_REGION_LIMIT * floorAndCeilingBlend)
+
+	return tcave_adj, centerRegionLimit_adj
+end
 
-local c_glowstone = minetest.get_content_id("nether:glowstone")
-local c_nethersand = minetest.get_content_id("nether:sand")
-local c_netherbrick = minetest.get_content_id("nether:brick")
-local c_netherrack = minetest.get_content_id("nether:rack")
 
 
 -- On-generated function
 
-minetest.register_on_generated(function(minp, maxp, seed)
-	if minp.y > NETHER_DEPTH then
+local tunnelCandidate_count = 0
+local tunnel_count = 0
+local total_chunk_count = 0
+local function on_generated(minp, maxp, seed)
+
+	if minp.y > NETHER_CEILING or maxp.y < NETHER_FLOOR then
 		return
 	end
 
-	local x1 = maxp.x
-	local y1 = maxp.y
-	local z1 = maxp.z
-	local x0 = minp.x
-	local y0 = minp.y
-	local z0 = minp.z
-
-	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
-	local area = VoxelArea:new{MinEdge = emin, MaxEdge = emax}
+	local vm, emerge_min, emerge_max = minetest.get_mapgen_object("voxelmanip")
+	local area = VoxelArea:new{MinEdge=emerge_min, MaxEdge=emerge_max}
 	local data = vm:get_data(dbuf)
 
-	local x11 = emax.x -- Limits of mapchunk plus mapblock shell
-	local y11 = emax.y
-	local z11 = emax.z
-	local x00 = emin.x
-	local y00 = emin.y
-	local z00 = emin.z
+	local x0, y0, z0 = minp.x, math_max(minp.y, NETHER_FLOOR),   minp.z
+	local x1, y1, z1 = maxp.x, math_min(maxp.y, NETHER_CEILING), maxp.z
 
-	local ystride = x1 - x0 + 1
-	local zstride = ystride * ystride
-	local chulens = {x = ystride, y = ystride, z = ystride}
-	local minposxyz = {x = x0, y = y0, z = z0}
+	local yCaveStride = x1 - x0 + 1
+	local zCaveStride = yCaveStride * yCaveStride
+	local chulens = {x = yCaveStride, y = yCaveStride, z = yCaveStride}
 
-	nobj_cave = nobj_cave or minetest.get_perlin_map(np_cave, chulens)
-	local nvals_cave = nobj_cave:get3dMap_flat(minposxyz, nbuf_cave)
+	nobj_cave = nobj_cave or minetest.get_perlin_map(mapgen.np_cave, chulens)
+	local nvals_cave = nobj_cave:get_3d_map_flat(minp, nbuf_cave)
 
-	for y = y00, y11 do -- Y loop first to minimise tcave calculations
-		local tcave
-		local in_chunk_y = false
-		if y >= y0 and y <= y1 then
-			if y > yblmax then
-				tcave = TCAVE + ((y - yblmax) / BLEND) ^ 2
-			else
-				tcave = TCAVE
-			end
-			in_chunk_y = true
-		end
+	local dungeonRooms = mapgen.build_dungeon_room_list(data, area) -- function from mapgen_dungeons.lua
+	local abs_cave_noise, abs_cave_noise_adjusted
 
-		for z = z00, z11 do
-			local vi = area:index(x00, y, z) -- Initial voxelmanip index
-			local ni
-			local in_chunk_yz = in_chunk_y and z >= z0 and z <= z1
+	local contains_nether = false
+	local contains_mantle = false
+	local contains_ocean  = false
 
-			for x = x00, x11 do
-				if in_chunk_yz and x == x0 then
-					-- Initial noisemap index
-					ni = (z - z0) * zstride + (y - y0) * ystride + 1
-				end
-				local in_chunk_yzx = in_chunk_yz and x >= x0 and x <= x1 -- In mapchunk
 
-				local id = data[vi] -- Existing node
-				-- Cave air, cave liquids and dungeons are overgenerated,
-				-- convert these throughout mapchunk plus shell
-				if id == c_air or -- Air and liquids to air
-						id == c_lava_source or
-						id == c_lava_flowing or
-						id == c_water_source or
-						id == c_water_flowing then
+	for y = y0, y1 do -- Y loop first to minimise tcave & lava-sea calculations
+
+		local sea_level, cavern_limit_distance = mapgen.find_nearest_lava_sealevel(y) -- function from mapgen_mantle.lua
+		local above_lavasea = y > sea_level
+		local below_lavasea = y < sea_level
+
+		local tcave_adj, centerRegionLimit_adj = mapgen.get_mapgenblend_adjustments(y)
+		local tcave   = TCAVE + tcave_adj
+		local tmantle = CENTER_REGION_LIMIT + centerRegionLimit_adj -- cavern_noise_adj already contains central_region_limit_adj, so tmantle is only for comparisons when cavern_noise_adj hasn't been added to the noise value
+
+		 -- cavern_noise_adj gets added to noise value instead of added to the limit np_noise
+		 -- is compared against, so subtract centerRegionLimit_adj instead of adding
+		local cavern_noise_adj =
+			CENTER_REGION_LIMIT * (cavern_limit_distance * cavern_limit_distance * cavern_limit_distance) -
+			centerRegionLimit_adj
+
+		for z = z0, z1 do
+			local vi = area:index(x0, y, z) -- Initial voxelmanip index
+			local ni = (z - z0) * zCaveStride + (y - y0) * yCaveStride + 1
+			local noise2di = 1 + (z - z0) * yCaveStride
+
+			for x = x0, x1 do
+
+				local cave_noise = nvals_cave[ni]
+
+				if cave_noise > tcave then
+					-- Prime region
+					-- This was the only region in initial versions of the Nether mod.
+					-- It is the only region which portals from the surface will open into,
+					-- getting to any other regions in the Nether will require Shanks' Pony.
 					data[vi] = c_air
-				-- Dungeons are preserved so we don't need
-				-- to check for cavern in the shell
-				elseif id == c_cobble or -- Dungeons (preserved) to netherbrick
-						id == c_mossycobble or
-						id == c_stair_cobble then
-					data[vi] = c_netherbrick
-				end
+					contains_nether = true
 
-				if in_chunk_yzx then -- In mapchunk
-					if nvals_cave[ni] > tcave then -- Only excavate cavern in mapchunk
+				elseif -cave_noise > tcave then
+					-- Secondary/spare region
+					-- This secondary region is unused until someone decides to do something cool or novel with it.
+					-- Reaching here would require the player to first find and journey through the central region,
+					-- as it's always separated from the Prime region by the central region.
+
+					data[vi] = mapgen.getGeodeInteriorNodeId(x, y, z)-- function from mapgen_geodes.lua
+
+					-- Only set contains_nether to true here if you want tunnels created between the secondary region
+					-- and the central region.
+					contains_nether = true
+				else
+					-- netherrack walls and/or center region/mantle
+					abs_cave_noise = math_abs(cave_noise)
+
+					-- abs_cave_noise_adjusted makes the center region smaller as distance from the lava ocean
+					-- increases, we do this by pretending the abs_cave_noise value is higher.
+					abs_cave_noise_adjusted = abs_cave_noise + cavern_noise_adj
+
+					if abs_cave_noise_adjusted >= CENTER_CAVERN_LIMIT then
+
+						local id = data[vi] -- Check existing node to avoid removing dungeons
+						if id == c_air or id == c_native_mapgen then
+							if abs_cave_noise < tmantle then
+								data[vi] = c_netherrack_deep
+							else
+								-- the shell seperating the mantle from the rest of the nether...
+								if cave_noise > 0 then
+									data[vi] = c_netherrack -- excavate_dungeons() will mostly reverse this inside dungeons
+								else
+									data[vi] = c_crystaldark
+								end
+							end
+						end
+
+					elseif above_lavasea then
 						data[vi] = c_air
-					elseif id == c_mese then -- Mese block to lava
-						data[vi] = c_lava_source
-					elseif id == c_stone_with_gold or -- Precious ores to glowstone
-							id == c_stone_with_mese or
-							id == c_stone_with_diamond then
-						data[vi] = c_glowstone
-					elseif id == c_gravel or -- Blob ore to nethersand
-							id == c_dirt or
-							id == c_sand then
-						data[vi] = c_nethersand
-					else -- All else to netherstone
-						data[vi] = c_netherrack
+						contains_mantle = true
+					elseif abs_cave_noise_adjusted < SURFACE_CRUST_LIMIT or (below_lavasea and abs_cave_noise_adjusted < CRUST_LIMIT) then
+						data[vi] = c_lavasea_source
+						contains_ocean = true
+					else
+						data[vi] = c_lava_crust
+						contains_ocean = true
 					end
-
-					ni = ni + 1 -- Only increment noise index in mapchunk
 				end
 
+				ni = ni + 1
 				vi = vi + 1
+				noise2di = noise2di + 1
 			end
 		end
 	end
 
+	if contains_mantle or contains_ocean then
+		mapgen.add_basalt_columns(data, area, minp, maxp) -- function from mapgen_mantle.lua
+	end
+
+	if contains_nether and contains_mantle then
+		tunnelCandidate_count = tunnelCandidate_count + 1
+		local success = mapgen.excavate_tunnel_to_center_of_the_nether(data, area, nvals_cave, minp, maxp) -- function from mapgen_mantle.lua
+		if success then tunnel_count = tunnel_count + 1 end
+	end
+	total_chunk_count = total_chunk_count + 1
+	if total_chunk_count % 50 == 0 then
+		debugf(
+			"%s of %s chunks contain both nether and lava-sea (%s%%), %s chunks generated a pathway (%s%%)",
+			tunnelCandidate_count,
+			total_chunk_count,
+			math_floor(tunnelCandidate_count * 100 / total_chunk_count),
+			tunnel_count,
+			math_floor(tunnel_count * 100 / total_chunk_count)
+		)
+	end
+
+	-- any air from the native mapgen has been replaced by netherrack, but we
+	-- don't want netherrack inside dungeons, so fill known dungeon rooms with air.
+	mapgen.excavate_dungeons(data, area, dungeonRooms) -- function from mapgen_dungeons.lua
+	mapgen.decorate_dungeons(data, area, dungeonRooms) -- function from mapgen_dungeons.lua
+
 	vm:set_data(data)
-	vm:set_lighting({day = 0, night = 0})
+
+	minetest.generate_ores(vm)
+	minetest.generate_decorations(vm)
+
+	vm:set_lighting({day = 0, night = 0}, minp, maxp)
 	vm:calc_lighting()
 	vm:update_liquids()
 	vm:write_to_map()
-end)
+end
 
 
 -- use knowledge of the nether mapgen algorithm to return a suitable ground level for placing a portal.
-function nether.find_nether_ground_y(target_x, target_z, start_y)
-	local nobj_cave_point = minetest.get_perlin(np_cave)
+-- player_name is optional, allowing a player to spawn a remote portal in their own protected areas.
+function nether.find_nether_ground_y(target_x, target_z, start_y, player_name)
+	local nobj_cave_point = mapgen.get_cave_point_perlin()
 	local air = 0 -- Consecutive air nodes found
 
-	for y = start_y, start_y - 4096, -1 do
-		local nval_cave = nobj_cave_point:get3d({x = target_x, y = y, z = target_z})
+	local minp_schem, maxp_schem = nether.get_schematic_volume({x = target_x, y = 0, z = target_z}, nil, "nether_portal")
+	local minp = {x = minp_schem.x, y = 0, z = minp_schem.z}
+	local maxp = {x = maxp_schem.x, y = 0, z = maxp_schem.z}
+
+	for y = start_y, math_max(NETHER_FLOOR + BLEND, start_y - 4096), -1 do
+		local nval_cave = nobj_cave_point:get_3d({x = target_x, y = y, z = target_z})
 
 		if nval_cave > TCAVE then -- Cavern
 			air = air + 1
 		else -- Not cavern, check if 4 nodes of space above
 			if air >= 4 then
+				local portal_y = y + 1
 				-- Check volume for non-natural nodes
-				local minp = {x = target_x - 1, y = y    , z = target_z - 2}
-				local maxp = {x = target_x + 2, y = y + 4, z = target_z + 2}
-				if nether.volume_is_natural(minp, maxp) then
-					return y + 1
+				minp.y = minp_schem.y + portal_y
+				maxp.y = maxp_schem.y + portal_y
+				if nether.volume_is_natural_and_unprotected(minp, maxp, player_name) then
+					return portal_y
 				else -- Restart search a little lower
-					nether.find_nether_ground_y(target_x, target_z, y - 16)
+					nether.find_nether_ground_y(target_x, target_z, y - 16, player_name)
 				end
 			else -- Not enough space, reset air to zero
 				air = 0
@@ -221,5 +517,7 @@ function nether.find_nether_ground_y(target_x, target_z, start_y)
 		end
 	end
 
-	return start_y -- Fallback
-end
+	return math_max(start_y, NETHER_FLOOR + BLEND) -- Fallback
+end
+
+minetest.register_on_generated(on_generated)

mapgen_decorations.lua

@@ -0,0 +1,592 @@
+--[[
+
+  Register decorations for Nether mapgen
+
+  Copyright (C) 2020 Treer
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+-- Lava is unreliable in the old Nether mapgen because it removes lava
+-- from the overdraw areas, so any decorations involving lava will often
+-- have the lava missing depending on whether nearby chunks were already
+-- emerged or not before the decoration was placed.
+local allow_lava_decorations = nether.useBiomes
+
+-- Keep compatibility with mapgen_nobiomes.lua, so hardcoding 128
+-- instead of using nether.mapgen.BLEND
+local decoration_ceiling = nether.DEPTH_CEILING - 128
+local decoration_floor   = nether.DEPTH_FLOOR   + 128
+
+local _  = {name = "air",                     prob = 0}
+local A  = {name = "air",                     prob = 255, force_place = true}
+local G  = {name = "nether:glowstone",        prob = 255, force_place = true}
+local N  = {name = "nether:rack",             prob = 255}
+local D  = {name = "nether:rack_deep",        prob = 255}
+local S  = {name = "nether:sand",             prob = 255, force_place = true}
+local L  = {name = "default:lava_source",     prob = 255, force_place = true}
+local F  = {name = "nether:fumarole",         prob = 255, force_place = true}
+local FS = {name = "nether:fumarole_slab",    prob = 255, force_place = true}
+local F1 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 0}
+local F2 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 1}
+local F3 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 2}
+local F4 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 3}
+local S1 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 5}
+local S2 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 7}
+local S3 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 12}
+local S4 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 16}
+
+
+-- =================
+--    Stalactites
+-- =================
+
+local schematic_GlowstoneStalactite = {
+    size = {x = 5, y = 10, z = 5},
+    data = { -- note that data is upside down
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, N, G, N, _,
+        _, N, N, N, _,
+
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, G, _, _,
+        _, _, G, _, _,
+        _, G, G, G, _,
+        N, G, G, G, N,
+        N, N, G, N, N,
+
+        _, _, N, _, _,   -- ypos 0, prob 25% (64/256)
+        _, _, G, _, _,   -- ypos 1, prob 37% (96/256)
+        _, _, G, _, _,   -- ypos 2, prob 100%
+        _, _, G, _, _,   -- ypos 3, prob 100%
+        _, _, G, G, _,   -- ypos 4, prob 50% (128/256) to make half of stalactites asymmetric
+        _, G, G, G, _,   -- ypos 5, prob 75% (192/256)
+        _, G, G, G, _,   -- ypos 6, prob 75% (192/256)
+        _, G, G, G, _,   -- ypos 7, prob 100%
+        G, G, G, G, G,   -- ypos 8, prob 100%
+        N, G, G, G, N,   -- ypos 9, prob 75% (192/256)
+
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, G, _, _,
+        _, _, G, _, _,
+        _, _, G, _, _,
+        _, G, G, G, _,
+        N, G, G, G, N,
+        N, N, G, N, N,
+
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, _, _, _, _,
+        _, N, G, N, _,
+        _, N, N, N, _
+    },
+    -- Y-slice probabilities do not function correctly for ceiling schematic
+    -- decorations because they are inverted, so ypos numbers have been inverted
+    -- to match, and a larger offset in place_offset_y should be used (e.g. -3).
+    yslice_prob = {
+        {ypos = 9, prob = 192},
+        {ypos = 6, prob = 192},
+        {ypos = 5, prob = 192},
+        {ypos = 4, prob = 128},
+        {ypos = 1, prob = 96},
+        {ypos = 0, prob = 64}
+    }
+}
+
+minetest.register_decoration({
+    name = "Glowstone stalactite",
+    deco_type = "schematic",
+    place_on = "nether:rack",
+    sidelen = 80,
+    fill_ratio = 0.0003,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_GlowstoneStalactite,
+    flags = "place_center_x,place_center_z,force_placement,all_ceilings",
+    place_offset_y=-3
+})
+
+minetest.register_decoration({
+    name = "Netherrack stalactite",
+    deco_type = "schematic",
+    place_on = "nether:rack",
+    sidelen = 80,
+    fill_ratio = 0.0008,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_GlowstoneStalactite,
+    replacements = {["nether:glowstone"] = "nether:rack"},
+    flags = "place_center_x,place_center_z,all_ceilings",
+    place_offset_y=-3
+})
+
+
+local schematic_GreaterStalactite = {
+    size = {x = 3, y = 23, z = 3},
+    data = { -- note that data is upside down
+
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, D, _,
+        _, D, _,
+        _, D, _,
+        _, D, _,
+        D, D, D,
+        D, D, D,
+        D, D, D,
+        _, D, _,
+        _, _, _,
+        _, _, _,
+
+        _, D, _,  -- ypos 0, prob 85% (218/255)
+        _, D, _,  -- ypos 1, prob 85% (218/255)
+        _, D, _,  -- ypos 2, prob 85% (218/255)
+        _, D, _,  -- ypos 3, prob 85% (218/255)
+        _, D, _,  -- ypos 4, prob 85% (218/255)
+        _, D, _,  -- ypos 5, prob 85% (218/255)
+        _, D, _,  -- ypos 6, prob 85% (218/255)
+        _, D, _,  -- ypos 7, prob 85% (218/255)
+        _, D, _,  -- ypos 8, prob 85% (218/255)
+        _, D, D,  -- ypos 9, prob 50% (128/256) to make half of stalactites asymmetric
+        _, D, D,  -- ypos 10, prob 50% (128/256) to make half of stalactites asymmetric
+        _, D, D,  -- ypos 11, prob 50% (128/256) to make half of stalactites asymmetric
+        _, D, D,  -- ypos 12, prob 50% (128/256) to make half of stalactites asymmetric
+        D, D, D,  -- ypos 13, prob 75% (192/256)
+        D, D, D,  -- ypos 14, prob 75% (192/256)
+        D, D, D,  -- ypos 15, prob 100%
+        D, D, D,  -- ypos 16, prob 100%
+        D, D, D,  -- ypos 17, prob 100%
+        D, D, D,  -- ypos 18, prob 100%
+        D, D, D,  -- ypos 19, prob 75% (192/256)
+        D, D, D,  -- ypos 20, prob 85% (218/255)
+        _, D, D,  -- ypos 21, prob 50% (128/256) to make half of stalactites asymmetric
+        _, D, _,  -- ypos 22, prob 100%
+
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, _, _,
+        _, D, _,
+        _, D, _,
+        _, D, _,
+        _, D, _,
+        _, D, _,
+        D, D, D,
+        D, D, D,
+        D, D, D,
+        _, D, _,
+        _, D, _,
+        _, _, _,
+
+    },
+    -- Y-slice probabilities do not function correctly for ceiling schematic
+    -- decorations because they are inverted, so ypos numbers have been inverted
+    -- to match, and a larger offset in place_offset_y should be used (e.g. -3).
+    yslice_prob = {
+        {ypos = 21, prob = 128},
+        {ypos = 20, prob = 218},
+        {ypos = 19, prob = 192},
+        {ypos = 14, prob = 192},
+        {ypos = 13, prob = 192},
+        {ypos = 12, prob = 128},
+        {ypos = 11, prob = 128},
+        {ypos = 10, prob = 128},
+        {ypos =  9, prob = 128},
+        {ypos =  8, prob = 218},
+        {ypos =  7, prob = 218},
+        {ypos =  6, prob = 218},
+        {ypos =  5, prob = 218},
+        {ypos =  4, prob = 218},
+        {ypos =  3, prob = 218},
+        {ypos =  2, prob = 218},
+        {ypos =  1, prob = 218},
+        {ypos =  0, prob = 218}
+    }
+}
+
+
+
+-- A stalagmite is an upsidedown stalactite, so
+-- use the GreaterStalactite to create a ToweringStalagmite schematic
+local schematic_ToweringStalagmite = {
+    size = schematic_GreaterStalactite.size,
+    data = {},
+    yslice_prob = {}
+}
+local array_length = #schematic_GreaterStalactite.data + 1
+for i, node in ipairs(schematic_GreaterStalactite.data) do
+    schematic_ToweringStalagmite.data[array_length - i] = node
+end
+y_size = schematic_GreaterStalactite.size.y
+for i, node in ipairs(schematic_GreaterStalactite.yslice_prob) do
+    schematic_ToweringStalagmite.yslice_prob[i] = {
+        -- we can safely lower the prob. to gain more variance because floor based schematics
+        -- don't have the bug where missing lines moves them away from the surface
+        prob = schematic_GreaterStalactite.yslice_prob[i].prob - 20,
+        ypos = y_size - 1 - schematic_GreaterStalactite.yslice_prob[i].ypos
+    }
+end
+
+minetest.register_decoration({
+    name = "Deep-glowstone stalactite",
+    deco_type = "schematic",
+    place_on = "nether:rack_deep",
+    sidelen = 80,
+    fill_ratio = 0.0003,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_GlowstoneStalactite,
+    replacements = {["nether:rack"] = "nether:rack_deep", ["nether:glowstone"] = "nether:glowstone_deep"},
+    flags = "place_center_x,place_center_z,force_placement,all_ceilings",
+    place_offset_y=-3
+})
+
+minetest.register_decoration({
+    name = "Deep-glowstone stalactite outgrowth",
+    deco_type = "schematic",
+    place_on = "nether:glowstone_deep",
+    sidelen = 40,
+    fill_ratio = 0.15,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = {
+        size = {x = 1, y = 4, z = 1},
+        data = { G, G, G, G }
+    },
+    replacements = {["nether:glowstone"] = "nether:glowstone_deep"},
+    flags = "place_center_x,place_center_z,all_ceilings",
+})
+
+minetest.register_decoration({
+    name = "Deep-netherrack stalactite",
+    deco_type = "schematic",
+    place_on = "nether:rack_deep",
+    sidelen = 80,
+    fill_ratio = 0.0003,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_GlowstoneStalactite,
+    replacements = {["nether:rack"] = "nether:rack_deep", ["nether:glowstone"] = "nether:rack_deep"},
+    flags = "place_center_x,place_center_z,force_placement,all_ceilings",
+    place_offset_y=-3
+})
+
+minetest.register_decoration({
+    name = "Deep-netherrack towering stalagmite",
+    deco_type = "schematic",
+    place_on = "nether:rack_deep",
+    sidelen = 80,
+    fill_ratio = 0.001,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_ToweringStalagmite,
+    replacements = {["nether:basalt"] = "nether:rack_deep"},
+    flags = "place_center_x,place_center_z,force_placement,all_floors",
+    place_offset_y=-2
+})
+
+-- =======================================
+--    Concealed crevice / Lava sinkhole
+-- =======================================
+-- if player places a torch/block on this sand or digs it while standing on it, it sinks into lava
+
+if allow_lava_decorations then
+    minetest.register_decoration({
+        name = "Weak trap",
+        deco_type = "schematic",
+        place_on = "nether:rack",
+        sidelen = 80,
+        fill_ratio = 0.002,
+        biomes = {"nether_caverns"},
+        y_max = decoration_ceiling,
+        y_min = decoration_floor,
+        schematic = {
+            size = {x = 4, y = 7, z = 4},
+            data = { -- note that data is upside down
+                _, _, _, _,
+                _, _, _, _,
+                _, N, _, _,
+                _, N, N, _,
+                _, N, N, _,
+                _, N, N, _,
+                _, _, _, _,
+
+                _, N, _, _, -- make it look like a stalactite if it protrudes out the bottom of a landform
+                _, N, _, _,
+                N, L, N, _,
+                N, L, L, N,
+                N, L, L, N,
+                N, A, A, N,
+                _, S, S, _,
+
+                _, _, _, _,
+                _, _, _, _,
+                _, N, N, _,
+                N, L, L, N,
+                N, L, L, N,
+                N, A, A, N,
+                _, S, S, _,
+
+                _, _, _, _,
+                _, _, _, _,
+                _, _, _, _,
+                _, N, N, _,
+                _, N, N, _,
+                _, N, N, _,
+                _, _, _, _,
+            }
+        },
+        replacements = {["nether:glowstone"] = "nether:rack"},
+        flags = "place_center_x,place_center_z,force_placement, all_floors",
+        place_offset_y=-6,
+        rotation = "random"
+    })
+end
+
+
+-- ==========================
+--    Fumaroles (Chimneys)
+-- ==========================
+
+
+local replacements_slab = {}
+local replacements_full = {["nether:fumarole_slab"] = "nether:fumarole"}
+
+if allow_lava_decorations then
+    -- Minetest engine limitations mean any mesh or nodebox node (like nether:fumarole)
+    -- will light up if it has lava below it, so replace the air node over the lava with
+    -- a node that prevents light propagation.
+    -- (Unfortunately this also means if a player digs down to get the lava block it'll
+    -- look like the lighting wasn't set in the block above the lava)
+    replacements_slab["air"] = "nether:airlike_darkness"
+    replacements_full["air"] = "nether:airlike_darkness"
+else
+    -- Lava is frequently removed by the old mapgen, so put sand at the bottom
+    -- of fumaroles.
+    replacements_slab["default:lava_source"] = "nether:sand"
+    replacements_full["default:lava_source"] = "nether:sand"
+end
+
+
+local schematic_fumarole = {
+    size = {x = 3, y = 5, z = 3},
+    data = { -- note that data is upside down
+        _, _, _,
+        _, N, _,
+        _, N, _,
+        _, _, _,
+        _, _, _,
+
+        _, N, _,
+        N, L, N,
+        N, A, N,
+        _, F, _,
+        _,FS, _,
+
+        _, _, _,
+        _, N, _,
+        _, N, _,
+        _, _, _,
+        _, _, _,
+    },
+}
+
+-- Common fumarole decoration that's flush with the floor and spawns everywhere
+
+minetest.register_decoration({
+    name = "Sunken nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 80,
+    fill_ratio = 0.005,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_fumarole,
+    replacements = replacements_full,
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y=-4
+})
+
+
+-- Rarer formations of raised fumaroles in clumps
+
+local fumarole_clump_noise_offset = -0.58
+local fumarole_clump_noise = {
+    offset = fumarole_clump_noise_offset,
+    scale = 0.5,
+    spread = {x = 40, y = 40, z = 15},
+    octaves = 4,
+    persist = 0.65,
+    lacunarity = 2.0,
+}
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset - 0.035
+minetest.register_decoration({
+    name = "Raised Nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_fumarole,
+    replacements = replacements_full,
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y=-3
+})
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset
+minetest.register_decoration({
+    name = "Half-raised Nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = schematic_fumarole,
+    replacements = replacements_slab,
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y=-3
+})
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset - 0.035
+minetest.register_decoration({
+    name = "Nether fumarole mound",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = {
+        size = {x = 4, y = 4, z = 4},
+        data = { -- note that data is upside down
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+
+            _, S,  S,  _,
+            N, A,  A,  N,
+            _, S2, S1, _,
+            _, F2, F1, _,
+
+            _, S,  S,  _,
+            N, A,  A,  N,
+            _, S3, S4, _,
+            _, F3, F4, _,
+
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _
+        },
+        yslice_prob = {{ypos = 3, prob = 192}} -- occasionally leave the fumarole cap off
+    },
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y = -2
+})
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset - 0.01
+minetest.register_decoration({
+    name = "Double Nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = decoration_ceiling,
+    y_min = decoration_floor,
+    schematic = {
+        size = {x = 4, y = 5, z = 4},
+        data = { -- note that data is upside down
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+
+            _, S,  S,  _,
+            N, A,  A,  N,
+            _, S2, S1, _,
+            _, F2, F,  _,
+            _, _,  FS, _,
+
+            _, S,  S,  _,
+            F, A,  A,  N, -- the F may add slight variance in landforms where it gets exposed
+            _, S3, S4, _,
+            _, F3, F4, _,
+            _, _,  _,  _,
+
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+            _, _,  _,  _
+        }
+    },
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y = -2,
+    rotation = "random"
+})

mapgen_dungeons.lua

@@ -0,0 +1,334 @@
+--[[
+
+  Nether mod for minetest
+
+  All the Dungeon related functions used by the biomes-based mapgen are here.
+
+
+  Copyright (C) 2021 Treer
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+
+-- We don't need to be gen-notified of temples because only dungeons will be generated
+-- if a biome defines the dungeon nodes
+minetest.set_gen_notify({dungeon = true})
+
+
+-- Content ids
+
+local c_air              = minetest.get_content_id("air")
+local c_netherrack       = minetest.get_content_id("nether:rack")
+local c_netherrack_deep  = minetest.get_content_id("nether:rack_deep")
+local c_crystaldark      = minetest.get_content_id("nether:geode")
+local c_dungeonbrick     = minetest.get_content_id("nether:brick")
+local c_dungeonbrick_alt = minetest.get_content_id("nether:brick_cracked")
+local c_netherbrick_slab = minetest.get_content_id("stairs:slab_nether_brick")
+local c_netherfence      = minetest.get_content_id("nether:fence_nether_brick")
+local c_glowstone        = minetest.get_content_id("nether:glowstone")
+local c_glowstone_deep   = minetest.get_content_id("nether:glowstone_deep")
+local c_lava_source      = minetest.get_content_id("default:lava_source")
+
+
+-- Misc math functions
+
+-- avoid needing table lookups each time a common math function is invoked
+local math_max, math_min  = math.max, math.min
+
+
+-- Dungeon excavation functions
+
+function is_dungeon_brick(node_id)
+	return node_id == c_dungeonbrick or node_id == c_dungeonbrick_alt
+end
+
+
+
+nether.mapgen.build_dungeon_room_list = function(data, area)
+
+	local result = {}
+
+	-- Unfortunately gennotify only returns dungeon rooms, not corridors.
+	-- We don't need to check for temples because only dungeons are generated in biomes
+	-- that define their own dungeon nodes.
+	local gennotify = minetest.get_mapgen_object("gennotify")
+	local roomLocations = gennotify["dungeon"] or {}
+
+	-- Excavation should still know to stop if a cave or corridor has removed the dungeon wall.
+	-- See MapgenBasic::generateDungeons in mapgen.cpp for max room sizes.
+	local maxRoomSize = 18
+	local maxRoomRadius = math.ceil(maxRoomSize / 2)
+
+	local xStride, yStride, zStride = 1, area.ystride, area.zstride
+	local minEdge, maxEdge = area.MinEdge, area.MaxEdge
+
+	for _, roomPos in ipairs(roomLocations) do
+
+		if area:containsp(roomPos) then -- this safety check does not appear to be necessary, but lets make it explicit
+
+			local room_vi = area:indexp(roomPos)
+			--data[room_vi] = minetest.get_content_id("default:torch") -- debug
+
+			local startPos = vector.new(roomPos)
+			if roomPos.y + 1 <= maxEdge.y and data[room_vi + yStride] == c_air then
+				-- The roomPos coords given by gennotify are at floor level, but whenever possible we
+				-- want to be performing searches a node higher than floor level to avoids dungeon chests.
+				startPos.y = startPos.y + 1
+				room_vi = area:indexp(startPos)
+			end
+
+			local bound_min_x = math_max(minEdge.x, roomPos.x - maxRoomRadius)
+			local bound_min_y = math_max(minEdge.y, roomPos.y - 1) -- room coords given by gennotify are on the floor
+			local bound_min_z = math_max(minEdge.z, roomPos.z - maxRoomRadius)
+
+			local bound_max_x = math_min(maxEdge.x, roomPos.x + maxRoomRadius)
+			local bound_max_y = math_min(maxEdge.y, roomPos.y + maxRoomSize) -- room coords given by gennotify are on the floor
+			local bound_max_z = math_min(maxEdge.z, roomPos.z + maxRoomRadius)
+
+			local room_min = vector.new(startPos)
+			local room_max = vector.new(startPos)
+
+			local vi = room_vi
+			while room_max.y < bound_max_y and data[vi + yStride] == c_air do
+				room_max.y = room_max.y + 1
+				vi = vi + yStride
+			end
+
+			vi = room_vi
+			while room_min.y > bound_min_y and data[vi - yStride] == c_air do
+				room_min.y = room_min.y - 1
+				vi = vi - yStride
+			end
+
+			vi = room_vi
+			while room_max.z < bound_max_z and data[vi + zStride] == c_air do
+				room_max.z = room_max.z + 1
+				vi = vi + zStride
+			end
+
+			vi = room_vi
+			while room_min.z > bound_min_z and data[vi - zStride] == c_air do
+				room_min.z = room_min.z - 1
+				vi = vi - zStride
+			end
+
+			vi = room_vi
+			while room_max.x < bound_max_x and data[vi + xStride] == c_air do
+				room_max.x = room_max.x + 1
+				vi = vi + xStride
+			end
+
+			vi = room_vi
+			while room_min.x > bound_min_x and data[vi - xStride] == c_air do
+				room_min.x = room_min.x - 1
+				vi = vi - xStride
+			end
+
+			local roomInfo = vector.new(roomPos)
+			roomInfo.minp = room_min
+			roomInfo.maxp = room_max
+			result[#result + 1] = roomInfo
+		end
+	end
+
+	return result;
+end
+
+-- Only partially excavates dungeons, the rest is left as an exercise for the player ;)
+-- (Corridors and the parts of rooms which extend beyond the emerge boundary will remain filled)
+nether.mapgen.excavate_dungeons = function(data, area, rooms)
+
+	local vi, node_id
+
+	-- any air from the native mapgen has been replaced by netherrack, but
+	-- we don't want this inside dungeons, so fill dungeon rooms with air
+	for _, roomInfo in ipairs(rooms) do
+
+		local room_min = roomInfo.minp
+		local room_max = roomInfo.maxp
+
+		for z = room_min.z, room_max.z do
+			for y = room_min.y, room_max.y do
+				vi = area:index(room_min.x, y, z)
+				for x = room_min.x, room_max.x do
+					node_id = data[vi]
+					if node_id == c_netherrack or node_id == c_netherrack_deep or node_id == c_crystaldark then data[vi] = c_air end
+					vi = vi + 1
+				end
+			end
+		end
+	end
+
+	-- clear netherrack from dungeon stairways
+	if #rooms > 0 then
+		local stairPositions = minetest.find_nodes_in_area(area.MinEdge, area.MaxEdge, minetest.registered_biomes["nether_caverns"].node_dungeon_stair)
+		for _, stairPos in ipairs(stairPositions) do
+			vi = area:indexp(stairPos)
+			for i = 1, 4 do
+				if stairPos.y + i > area.MaxEdge.y then break end
+				vi = vi + area.ystride
+				node_id = data[vi]
+				-- searching forward of the stairs could also be done
+				if node_id == c_netherrack or node_id == c_netherrack_deep or node_id == c_crystaldark then data[vi] = c_air end
+			end
+		end
+	end
+end
+
+-- Since we already know where all the rooms and their walls are, and have all the nodes stored
+-- in a voxelmanip already, we may as well add a little Nether flair to the dungeons found here.
+nether.mapgen.decorate_dungeons = function(data, area, rooms)
+
+	local xStride, yStride, zStride = 1, area.ystride, area.zstride
+	local minEdge, maxEdge = area.MinEdge, area.MaxEdge
+
+	for _, roomInfo in ipairs(rooms) do
+
+		local room_min, room_max = roomInfo.minp, roomInfo.maxp
+		local room_size = vector.distance(room_min, room_max)
+
+		if room_size > 10 then
+			local room_seed = roomInfo.x + 3 * roomInfo.z + 13 * roomInfo.y
+			local window_y  = roomInfo.y + math_min(2, room_max.y - roomInfo.y - 1)
+			local roomWidth  = room_max.x - room_min.x + 1
+			local roomLength = room_max.z - room_min.z + 1
+
+			if room_seed % 3 == 0 and room_max.y < maxEdge.y then
+				-- Glowstone chandelier (feel free to replace with a fancy schematic)
+				local vi = area:index(roomInfo.x, room_max.y + 1, roomInfo.z)
+				if is_dungeon_brick(data[vi]) then data[vi] = c_glowstone end
+
+			elseif room_seed % 4 == 0 and room_min.y > minEdge.y
+				   and room_min.x > minEdge.x and room_max.x < maxEdge.x
+				   and room_min.z > minEdge.z and room_max.z < maxEdge.z then
+				-- lava well (feel free to replace with a fancy schematic)
+				local vi = area:index(roomInfo.x, room_min.y, roomInfo.z)
+				if is_dungeon_brick(data[vi - yStride]) then
+					data[vi - yStride] = c_lava_source
+					if data[vi - zStride] == c_air then data[vi - zStride] = c_netherbrick_slab end
+					if data[vi + zStride] == c_air then data[vi + zStride] = c_netherbrick_slab end
+					if data[vi - xStride] == c_air then data[vi - xStride] = c_netherbrick_slab end
+					if data[vi + xStride] == c_air then data[vi + xStride] = c_netherbrick_slab end
+				end
+			end
+
+			-- Barred windows
+			if room_seed % 7 < 5 and roomWidth >= 5 and roomLength >= 5
+			   and window_y >= minEdge.y and window_y + 1 <= maxEdge.y
+			   and room_min.x > minEdge.x and room_max.x < maxEdge.x
+			   and room_min.z > minEdge.z and room_max.z < maxEdge.z then
+				--data[area:indexp(roomInfo)] = minetest.get_content_id("default:mese_post_light") -- debug
+
+				-- Glass panes can't go in the windows because we aren't setting param data.
+				-- Until a Nether glass is added, every window will be made of netherbrick fence rather
+				-- than material depending on room_seed.
+				local window_node = c_netherfence
+				--if c_netherglass ~= nil and room_seed % 20 >= 12 then window_node = c_netherglass end
+
+				local function placeWindow(vi, viOutsideOffset, windowNo)
+					if is_dungeon_brick(data[vi]) and is_dungeon_brick(data[vi + yStride]) then
+						data[vi] = window_node
+
+						if room_seed % 19 == windowNo then
+							-- place a glowstone light behind the window
+							local node_id = data[vi + viOutsideOffset]
+							if node_id == c_netherrack then
+								data[vi + viOutsideOffset] = c_glowstone
+							elseif node_id == c_netherrack_deep then
+								data[vi + viOutsideOffset] = c_glowstone_deep
+							end
+						end
+					end
+				end
+
+				local vi_min = area:index(room_min.x - 1, window_y, roomInfo.z)
+				local vi_max = area:index(room_max.x + 1, window_y, roomInfo.z)
+				local locations = {-zStride, zStride, -zStride + yStride, zStride + yStride}
+				for i, offset in ipairs(locations) do
+					placeWindow(vi_min + offset, -1, i)
+					placeWindow(vi_max + offset,  1, i + #locations)
+				end
+				vi_min = area:index(roomInfo.x, window_y, room_min.z - 1)
+				vi_max = area:index(roomInfo.x, window_y, room_max.z + 1)
+				locations = {-xStride, xStride, -xStride + yStride, xStride + yStride}
+				for i, offset in ipairs(locations) do
+					placeWindow(vi_min + offset, -zStride, i + #locations * 2)
+					placeWindow(vi_max + offset,  zStride, i + #locations * 3)
+				end
+			end
+
+			-- pillars or mezzanine floor
+			if room_seed % 43 > 10 and roomWidth >= 6 and roomLength >= 6 then
+
+				local pillar_vi    = {}
+				local pillarHeight = 0
+				local wallDist = 1 + math.floor((roomWidth + roomLength) / 14)
+
+				local roomHeight = room_max.y - room_min.y
+				if roomHeight >= 7 then
+					-- mezzanine floor
+					local mezzMax = {
+						x = room_min.x + math.floor(roomWidth / 7 * 4),
+						y = room_min.y + math.floor(roomHeight / 5 * 3),
+						z = room_max.z
+					}
+
+					pillarHeight = mezzMax.y - room_min.y - 1
+					pillar_vi = {
+						area:index(mezzMax.x, room_min.y, room_min.z + wallDist),
+						area:index(mezzMax.x, room_min.y, room_max.z - wallDist),
+					}
+
+					if is_dungeon_brick(data[pillar_vi[1] - yStride]) and is_dungeon_brick(data[pillar_vi[2] - yStride]) then
+						-- The floor of the dungeon looks like it exists (i.e. not erased by nether
+						-- cavern), so add the mezzanine floor
+						for z = 0, roomLength - 1 do
+							local vi = area:index(room_min.x, mezzMax.y, room_min.z + z)
+							for x = room_min.x, mezzMax.x do
+								if data[vi] == c_air then data[vi] = c_dungeonbrick end
+								vi = vi + 1
+							end
+						end
+					end
+
+				elseif roomHeight >= 4 then
+					-- 4 pillars
+					pillarHeight = roomHeight
+					pillar_vi = {
+						area:index(room_min.x + wallDist, room_min.y, room_min.z + wallDist),
+						area:index(room_min.x + wallDist, room_min.y, room_max.z - wallDist),
+						area:index(room_max.x - wallDist, room_min.y, room_min.z + wallDist),
+						area:index(room_max.x - wallDist, room_min.y, room_max.z - wallDist)
+					}
+				end
+
+				for i = #pillar_vi, 1, -1 do
+					if not is_dungeon_brick(data[pillar_vi[i] - yStride]) then
+						-- there's no dungeon floor under this pillar so skip it, it's probably been cut away by nether cavern.
+						table.remove(pillar_vi, i)
+					end
+				end
+				for y = 0, pillarHeight do
+					for _, vi in ipairs(pillar_vi) do
+						if data[vi + y * yStride] == c_air then data[vi + y * yStride] = c_dungeonbrick end
+					end
+				end
+			end
+
+			-- Weeds on the floor once Nether weeds are added
+		end
+	end
+end

mapgen_geodes.lua

@@ -0,0 +1,221 @@
+--[[
+
+  Nether mod for minetest
+
+  This file contains helper functions for generating geode interiors,
+  a proof-of-concept to demonstrate how the secondary/spare region
+  in the nether might be put to use by someone.
+
+
+  Copyright (C) 2021 Treer
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+
+local debugf = nether.debug
+local mapgen = nether.mapgen
+
+
+-- Content ids
+
+local c_air              = minetest.get_content_id("air")
+local c_crystal          = minetest.get_content_id("nether:geodelite") -- geodelite has a faint glow
+local c_netherrack       = minetest.get_content_id("nether:rack")
+local c_glowstone        = minetest.get_content_id("nether:glowstone")
+
+-- Math funcs
+local math_max, math_min, math_abs, math_floor, math_pi = math.max, math.min, math.abs, math.floor, math.pi -- avoid needing table lookups each time a common math function is invoked
+
+
+-- Create a tiling space of close-packed spheres, using Hexagonal close packing
+-- of spheres with radius 0.5.
+-- With a layer of spheres on a flat surface, if the pack-z distance is 1 due to 0.5
+-- radius then the pack-x distance will be the height of an equilateral triangle: sqrt(3) / 2,
+-- and the pack-y distance between each layer will be sqrt(6) / 3,
+-- The tessellating space will be a rectangular box of 2*pack-x by 1*pack-z by 3*pack-y
+
+local xPack = math.sqrt(3)/2      -- 0.866, height of an equalateral triangle
+local xPack2 = xPack * 2          -- 1.732
+local yPack = math.sqrt(6) / 3    -- 0.816, y height of each layer
+local yPack2 = yPack * 2
+local yPack3 = yPack * 3
+local layer2offsetx = xPack / 3   -- 0.289, height to center of equalateral triangle
+local layer3offsetx = xPack2 / 3  -- 0.577
+local structureSize = 50 -- magic numbers may need retuning if this changes too much
+
+local layer1 = {
+    {0,      0,  0},
+    {0,      0,  1},
+    {xPack,  0, -0.5},
+    {xPack,  0,  0.5},
+    {xPack,  0,  1.5},
+    {xPack2, 0,  0},
+    {xPack2, 0,  1},
+}
+local layer2 = {
+    {layer2offsetx - xPack,  yPack,  0},
+    {layer2offsetx - xPack,  yPack,  1},
+    {layer2offsetx,          yPack, -0.5},
+    {layer2offsetx,          yPack,  0.5},
+    {layer2offsetx,          yPack,  1.5},
+    {layer2offsetx + xPack,  yPack,  0},
+    {layer2offsetx + xPack,  yPack,  1},
+    {layer2offsetx + xPack2, yPack, -0.5},
+    {layer2offsetx + xPack2, yPack,  0.5},
+    {layer2offsetx + xPack2, yPack,  1.5},
+}
+local layer3 = {
+    {layer3offsetx - xPack,  yPack2, -0.5},
+    {layer3offsetx - xPack,  yPack2,  0.5},
+    {layer3offsetx - xPack,  yPack2,  1.5},
+    {layer3offsetx,          yPack2,  0},
+    {layer3offsetx,          yPack2,  1},
+    {layer3offsetx + xPack,  yPack2, -0.5},
+    {layer3offsetx + xPack,  yPack2,  0.5},
+    {layer3offsetx + xPack,  yPack2,  1.5},
+    {layer3offsetx + xPack2, yPack2,  0},
+    {layer3offsetx + xPack2, yPack2,  1},
+}
+local layer4 = {
+    {0,      yPack3,  0},
+    {0,      yPack3,  1},
+    {xPack,  yPack3, -0.5},
+    {xPack,  yPack3,  0.5},
+    {xPack,  yPack3,  1.5},
+    {xPack2, yPack3,  0},
+    {xPack2, yPack3,  1},
+}
+local layers = {
+    {y = layer1[1][2], points = layer1}, -- layer1[1][2] is the y value of the first point in layer1, and all spheres in a layer have the same y
+    {y = layer2[1][2], points = layer2},
+    {y = layer3[1][2], points = layer3},
+    {y = layer4[1][2], points = layer4},
+}
+
+
+-- Geode mapgen functions (AKA proof of secondary/spare region concept)
+
+
+-- fast for small lists
+function insertionSort(array)
+    local i
+    for i = 2, #array do
+        local key = array[i]
+        local j = i - 1
+        while j > 0 and array[j] > key do
+            array[j + 1] = array[j]
+            j = j - 1
+        end
+        array[j + 1] = key
+    end
+    return array
+end
+
+
+local distSquaredList = {}
+local adj_x = 0
+local adj_y = 0
+local adj_z = 0
+local lasty, lastz
+local warpx, warpz
+
+
+-- It's quite a lot to calculate for each air node, but its not terribly slow and
+-- it'll be pretty darn rare for chunks in the secondary region to ever get emerged.
+mapgen.getGeodeInteriorNodeId = function(x, y, z)
+
+	if z ~= lastz then
+		lastz = z
+		-- Calculate structure warping
+		-- To avoid calculating this for each node there's no warping as you look along the x axis :(
+		adj_y = math.sin(math_pi / 222 * y) * 30
+
+		if y ~= lasty then
+			lasty = y
+			warpx = math.sin(math_pi / 100 * y) * 10
+			warpz = math.sin(math_pi /  43 * y) * 15
+		end
+		local twistRadians = math_pi / 73 * y
+		local sinTwist, cosTwist = math.sin(twistRadians), math.cos(twistRadians)
+		adj_x = cosTwist * warpx - sinTwist * warpz
+		adj_z = sinTwist * warpx + cosTwist * warpz
+	end
+
+	-- convert x, y, z into a position in the tessellating space
+	local cell_x = (((x + adj_x) / xPack2 + 0.5) % structureSize) / structureSize * xPack2
+	local cell_y = (((y + adj_y) / yPack3 + 0.5) % structureSize) / structureSize * yPack3
+	local cell_z = (((z + adj_z) + 0.5) % structureSize) / structureSize -- zPack = 1, so can be omitted
+
+	local iOut = 1
+	local i, j
+	local canSkip = false
+
+	for i = 1, #layers do
+
+		local layer = layers[i]
+		local dy = cell_y - layer.y
+
+		if dy > -0.71 and dy < 0.71 then -- optimization - don't include points to far away to make a difference. (0.71 comes from sin(45°))
+			local points = layer.points
+
+			for j = 1, #points do
+
+				local point = points[j]
+				local dx = cell_x - point[1]
+				local dz = cell_z - point[3]
+				local distSquared = dx*dx + dy*dy + dz*dz
+
+				if distSquared < 0.25 then
+					-- optimization - point is inside a sphere, so cannot be a wall edge. (0.25 comes from radius of 0.5 squared)
+					return c_air
+				end
+
+				distSquaredList[iOut] = distSquared
+				iOut = iOut + 1
+			end
+		end
+	end
+
+	-- clear the rest of the array instead of creating a new one to hopefully reduce luajit mem leaks.
+	while distSquaredList[iOut] ~= nil do
+		rawset(distSquaredList, iOut, nil)
+		iOut = iOut + 1
+	end
+
+	insertionSort(distSquaredList)
+
+	local d3_1 = distSquaredList[3] - distSquaredList[1]
+	local d3_2 = distSquaredList[3] - distSquaredList[2]
+	--local d4_1 = distSquaredList[4] - distSquaredList[1]
+	--local d4_3 = distSquaredList[4] - distSquaredList[3]
+
+	-- Some shape formulas (tuned for a structureSize of 50)
+	--   (d3_1 < 0.05) gives connective lines
+	--   (d3_1 < 0.05 or d3_2 < .02) give fancy elven bridges - prob doesn't need the d3_1 part
+	--  ((d3_1 < 0.05 or d3_2 < .02) and distSquaredList[1] > .3) tapers the fancy connections in the middle
+	--   (d4_3 < 0.03 and d3_2 < 0.03) produces caltrops at intersections
+	--   (d4_1 < 0.1) produces spherish balls at intersections
+	-- The idea is voronoi based - edges in a voronoi diagram are where each nearby point is at equal distance.
+	-- In this case we use squared distances to avoid calculating square roots.
+
+	if (d3_1 < 0.05 or d3_2 < .02) and distSquaredList[1] > .3 then
+		return c_crystal
+	elseif (distSquaredList[4] - distSquaredList[1]) < 0.08 then
+		return c_glowstone
+	else
+		return c_air
+	end
+end

mapgen_mantle.lua

@@ -0,0 +1,512 @@
+--[[
+
+  Nether mod for minetest
+
+  This file contains helper functions for generating the Mantle
+  (AKA center region), which are moved into a separate file to keep the
+  size of mapgen.lua manageable.
+
+
+  Copyright (C) 2021 Treer
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+
+local debugf = nether.debug
+local mapgen = nether.mapgen
+local S      = nether.get_translator
+
+local BASALT_COLUMN_UPPER_LIMIT = mapgen.BASALT_COLUMN_UPPER_LIMIT
+local BASALT_COLUMN_LOWER_LIMIT = mapgen.BASALT_COLUMN_LOWER_LIMIT
+
+
+-- 2D noise for basalt formations
+local np_basalt = {
+	offset      =-0.85,
+	scale       = 1,
+	spread      = {x = 46, y = 46, z = 46},
+	seed        = 1000,
+	octaves     = 5,
+	persistence = 0.5,
+	lacunarity  = 2.6,
+	flags = "eased"
+}
+
+
+-- Buffers and objects we shouldn't recreate every on_generate
+
+local nobj_basalt = nil
+local nbuf_basalt = {}
+
+-- Content ids
+
+local c_air              = minetest.get_content_id("air")
+local c_netherrack_deep  = minetest.get_content_id("nether:rack_deep")
+local c_glowstone        = minetest.get_content_id("nether:glowstone")
+local c_lavasea_source   = minetest.get_content_id("nether:lava_source") -- same as lava but with staggered animation to look better as an ocean
+local c_lava_crust       = minetest.get_content_id("nether:lava_crust")
+local c_basalt           = minetest.get_content_id("nether:basalt")
+
+
+-- Math funcs
+local math_max, math_min, math_abs, math_floor = math.max, math.min, math.abs, math.floor -- avoid needing table lookups each time a common math function is invoked
+
+function random_unit_vector()
+	return vector.normalize({
+		x = math.random() - 0.5,
+		y = math.random() - 0.5,
+		z = math.random() - 0.5
+	})
+end
+
+-- returns the smallest component in the vector
+function vector_min(v)
+	return math_min(v.x, math_min(v.y, v.z))
+end
+
+
+-- Mantle mapgen functions (AKA Center region)
+
+-- Returns (absolute height, fractional distance from ceiling or sea floor)
+-- the fractional distance from ceiling or sea floor is a value between 0 and 1 (inclusive)
+-- Note it may find the most relevent sea-level - not necesssarily the one you are closest
+-- to, since the space above the sea reaches much higher than the depth below the sea.
+mapgen.find_nearest_lava_sealevel = function(y)
+	-- todo: put oceans near the bottom of chunks to improve ability to generate tunnels to the center
+	-- todo: constrain y to be not near the bounds of the nether
+	-- todo: add some random adj at each level, seeded only by the level height
+	local sealevel = math.floor((y + 100) / 200) * 200
+	--local sealevel = math.floor((y + 80) / 160) * 160
+	--local sealevel = math.floor((y + 120) / 240) * 240
+
+	local cavern_limits_fraction
+	local height_above_sea = y - sealevel
+	if height_above_sea >= 0 then
+		cavern_limits_fraction = math_min(1, height_above_sea / 95)
+	else
+		-- approaches 1 much faster as the lava sea is shallower than the cavern above it
+		cavern_limits_fraction = math_min(1, -height_above_sea / 40)
+	end
+
+	return sealevel, cavern_limits_fraction
+end
+
+
+
+
+mapgen.add_basalt_columns = function(data, area, minp, maxp)
+	-- Basalt columns are structures found in lava oceans, and the only way to obtain
+	-- nether basalt.
+	-- Their x, z position is determined by a 2d noise map and a 2d slice of the cave
+	-- noise (taken at lava-sealevel).
+
+	local x0, y0, z0 = minp.x, math_max(minp.y, nether.DEPTH_FLOOR),   minp.z
+	local x1, y1, z1 = maxp.x, math_min(maxp.y, nether.DEPTH_CEILING), maxp.z
+
+	local yStride = area.ystride
+	local yCaveStride = x1 - x0 + 1
+
+	local cavePerlin = mapgen.get_cave_point_perlin()
+	nobj_basalt = nobj_basalt or minetest.get_perlin_map(np_basalt, {x = yCaveStride, y = yCaveStride})
+	local nvals_basalt = nobj_basalt:get_2d_map_flat({x=minp.x, y=minp.z}, {x=yCaveStride, y=yCaveStride}, nbuf_basalt)
+
+	local nearest_sea_level, _ = mapgen.find_nearest_lava_sealevel(math_floor((y0 + y1) / 2))
+
+	local leeway = mapgen.CENTER_CAVERN_LIMIT * 0.18
+
+	for z = z0, z1 do
+		local noise2di = 1 + (z - z0) * yCaveStride
+
+		for x = x0, x1 do
+
+			local basaltNoise = nvals_basalt[noise2di]
+			if basaltNoise > 0 then
+				-- a basalt column is here
+
+				local abs_sealevel_cave_noise = math_abs(cavePerlin:get_3d({x = x, y = nearest_sea_level, z = z}))
+
+				-- Add Some quick deterministic noise to the column heights
+				-- This is probably not good noise, but it doesn't have to be.
+				local fastNoise = 17
+				fastNoise = 37 * fastNoise + y0
+				fastNoise = 37 * fastNoise + z
+				fastNoise = 37 * fastNoise + x
+				fastNoise = 37 * fastNoise + math_floor(basaltNoise * 32)
+
+				local columnHeight = basaltNoise * 18 + ((fastNoise % 3) - 1)
+
+				-- columns should drop below sealevel where lava rivers are flowing
+				-- i.e. anywhere abs_sealevel_cave_noise < BASALT_COLUMN_LOWER_LIMIT
+				-- And we'll also have it drop off near the edges of the lava ocean so that
+				-- basalt columns can only be found by the player reaching a lava ocean.
+				local lowerClip = (math_min(math_max(abs_sealevel_cave_noise, BASALT_COLUMN_LOWER_LIMIT - leeway), BASALT_COLUMN_LOWER_LIMIT + leeway) - BASALT_COLUMN_LOWER_LIMIT) / leeway
+				local upperClip = (math_min(math_max(abs_sealevel_cave_noise, BASALT_COLUMN_UPPER_LIMIT - leeway), BASALT_COLUMN_UPPER_LIMIT + leeway) - BASALT_COLUMN_UPPER_LIMIT) / leeway
+				local columnHeightAdj = lowerClip * -upperClip -- all are values between 1 and -1
+
+				columnHeight = columnHeight + math_floor(columnHeightAdj * 12 - 12)
+
+				local vi = area:index(x, y0, z) -- Initial voxelmanip index
+
+				for y = y0, y1 do -- Y loop first to minimise tcave & lava-sea calculations
+
+					if y < nearest_sea_level + columnHeight  then
+
+						local id = data[vi] -- Existing node
+						if id == c_lava_crust or id == c_lavasea_source or (id == c_air and y > nearest_sea_level) then
+							-- Avoid letting columns extend beyond the central region.
+							-- (checking node ids saves having to calculate abs_cave_noise_adjusted here
+							-- to test it against CENTER_CAVERN_LIMIT)
+							data[vi] = c_basalt
+						end
+					end
+
+					vi = vi + yStride
+				end
+			end
+
+			noise2di = noise2di + 1
+		end
+	end
+end
+
+
+-- returns an array of points from pos1 and pos2 which deviate from a straight line
+-- but which don't venture too close to a chunk boundary
+function generate_waypoints(pos1, pos2, minp, maxp)
+
+	local segSize = 10
+	local maxDeviation = 7
+	local minDistanceFromChunkWall = 5
+
+	local pathVec     = vector.subtract(pos2, pos1)
+	local pathVecNorm = vector.normalize(pathVec)
+	local pathLength  = vector.distance(pos1, pos2)
+	local minBound    = vector.add(minp, minDistanceFromChunkWall)
+	local maxBound    = vector.subtract(maxp, minDistanceFromChunkWall)
+
+	local result = {}
+	result[1] = pos1
+
+	local segmentCount = math_floor(pathLength / segSize)
+	for i = 1, segmentCount do
+		local waypoint = vector.add(pos1, vector.multiply(pathVec, i / (segmentCount + 1)))
+
+		-- shift waypoint a few blocks in a random direction orthogonally to the pathVec, to make the path crooked.
+		local crossProduct
+		repeat
+			crossProduct = vector.normalize(vector.cross(pathVecNorm, random_unit_vector()))
+		until vector.length(crossProduct) > 0
+		local deviation = vector.multiply(crossProduct, math.random(1, maxDeviation))
+		waypoint = vector.add(waypoint, deviation)
+		waypoint = {
+			x = math_min(maxBound.x, math_max(minBound.x, waypoint.x)),
+			y = math_min(maxBound.y, math_max(minBound.y, waypoint.y)),
+			z = math_min(maxBound.z, math_max(minBound.z, waypoint.z))
+		}
+
+		result[#result + 1] = waypoint
+	end
+
+	result[#result + 1] = pos2
+	return result
+end
+
+
+function excavate_pathway(data, area, nether_pos, center_pos, minp, maxp)
+
+	local ystride = area.ystride
+	local zstride = area.zstride
+
+	math.randomseed(nether_pos.x + 10 * nether_pos.y + 100 * nether_pos.z) -- so each tunnel generates deterministically (this doesn't have to be a quality seed)
+	local dist = math_floor(vector.distance(nether_pos, center_pos))
+	local waypoints = generate_waypoints(nether_pos, center_pos, minp, maxp)
+
+	-- First pass: record path details
+	local linedata = {}
+	local last_pos = {}
+	local line_index = 1
+	local first_filled_index, boundary_index, last_filled_index
+	for i = 0, dist do
+		-- Bresenham's line would be good here, but too much lua code
+		local waypointProgress = (#waypoints - 1) * i / dist
+		local segmentIndex = math_min(math_floor(waypointProgress) + 1, #waypoints - 1) -- from the integer portion of waypointProgress
+		local segmentInterp = waypointProgress - (segmentIndex - 1)                     -- the remaining fractional portion
+		local segmentStart = waypoints[segmentIndex]
+		local segmentVector = vector.subtract(waypoints[segmentIndex + 1], segmentStart)
+		local pos = vector.round(vector.add(segmentStart, vector.multiply(segmentVector, segmentInterp)))
+
+		if not vector.equals(pos, last_pos) then
+			local vi = area:indexp(pos)
+			local node_id = data[vi]
+			linedata[line_index] = {
+				pos = pos,
+				vi = vi,
+				node_id = node_id
+			}
+			if boundary_index == nil and node_id == c_netherrack_deep then
+				boundary_index = line_index
+			end
+			if node_id == c_air then
+				if boundary_index ~= nil and last_filled_index == nil then
+					last_filled_index = line_index
+				end
+			else
+				if first_filled_index == nil then
+					first_filled_index = line_index
+				end
+			end
+			line_index = line_index + 1
+			last_pos = pos
+		end
+	end
+	first_filled_index = first_filled_index or 1
+	last_filled_index  = last_filled_index  or #linedata
+	boundary_index     = boundary_index     or last_filled_index
+
+
+	-- limit tunnel radius to roughly the closest that startPos or stopPos comes to minp-maxp, so we
+	-- don't end up exceeding minp-maxp and having excavation filled in when the next chunk is generated.
+	local startPos, stopPos = linedata[first_filled_index].pos, linedata[last_filled_index].pos
+	local radiusLimit = vector_min(vector.subtract(startPos, minp))
+	radiusLimit = math_min(radiusLimit, vector_min(vector.subtract(stopPos, minp)))
+	radiusLimit = math_min(radiusLimit, vector_min(vector.subtract(maxp, startPos)))
+	radiusLimit = math_min(radiusLimit, vector_min(vector.subtract(maxp, stopPos)))
+
+	if radiusLimit < 4 then -- This is a logic check, ignore it. It could be commented out
+		-- 4 is (79 - 75), and values less than 4 shouldn't be possible if sampling-skip was 10
+		-- i.e. if sampling-skip was 10 then {5, 15, 25, 35, 45, 55, 65, 75} should be sampled from possible positions 0 to 79
+		debugf("Error: radiusLimit %s is smaller then half the sampling distance. min %s, max %s, start %s, stop %s", radiusLimit, minp, maxp, startPos, stopPos)
+	end
+	radiusLimit = radiusLimit + 1 -- chunk walls wont be visibly flat if the radius only exceeds it a little ;)
+
+	-- Second pass: excavate
+	local start_index, stop_index = math_max(1, first_filled_index - 2), math_min(#linedata, last_filled_index + 3)
+	for i = start_index, stop_index, 3 do
+
+		-- Adjust radius so that tunnels start wide but thin out in the middle
+		local distFromEnds = 1 - math_abs(((start_index + stop_index) / 2) - i) / ((stop_index - start_index) / 2) -- from 0 to 1, with 0 at ends and 1 in the middle
+		-- Have it more flaired at the ends, rather than linear.
+		-- i.e. sizeAdj approaches 1 quickly as distFromEnds increases
+		local distFromMiddle = 1 - distFromEnds
+		local sizeAdj = 1 - (distFromMiddle * distFromMiddle * distFromMiddle)
+
+		local radius = math_min(radiusLimit, math.random(50 - (25 * sizeAdj), 80 - (45 * sizeAdj)) / 10)
+		local radiusSquared = radius * radius
+		local radiusCeil = math_floor(radius + 0.5)
+
+		linedata[i].radius = radius             -- Needed in third pass
+		linedata[i].distFromEnds = distFromEnds -- Needed in third pass
+
+		local vi = linedata[i].vi
+		for z = -radiusCeil, radiusCeil do
+			local vi_z = vi + z * zstride
+			for y = -radiusCeil, radiusCeil do
+				local vi_zy = vi_z + y * ystride
+				local xSquaredLimit = radiusSquared - (z * z + y * y)
+				for x = -radiusCeil, radiusCeil do
+					if x * x < xSquaredLimit then
+						data[vi_zy + x] = c_air
+					end
+				end
+			end
+		end
+
+	end
+
+	-- Third pass: decorate
+	-- Add glowstones to make tunnels to the mantle easier to find
+	-- https://i.imgur.com/sRA28x7.jpg
+	for i = start_index, stop_index, 3 do
+		if linedata[i].distFromEnds < 0.3 then
+			local glowcount = 0
+			local radius = linedata[i].radius
+			for _ = 1, 20 do
+				local testPos = vector.round(vector.add(linedata[i].pos, vector.multiply(random_unit_vector(), radius + 0.5)))
+				local vi = area:indexp(testPos)
+				if data[vi] ~= c_air then
+					data[vi] = c_glowstone
+					glowcount = glowcount + 1
+				--else
+				--	data[vi] = c_debug
+				end
+				if glowcount >= 2 then break end
+			end
+		end
+	end
+
+end
+
+
+-- excavates a tunnel connecting the Primary or Secondary region with the mantle / central region
+-- if a suitable path is found.
+-- Returns true if successful
+mapgen.excavate_tunnel_to_center_of_the_nether = function(data, area, nvals_cave, minp, maxp)
+
+	local result = false
+	local extent = vector.subtract(maxp, minp)
+	local skip = 10 -- sampling rate of 1 in 10
+
+	local highest = -1000
+	local lowest  =  1000
+	local lowest_vi
+	local highest_vi
+
+	local yCaveStride = maxp.x - minp.x + 1
+	local zCaveStride = yCaveStride * yCaveStride
+
+	local vi_offset = area:indexp(vector.add(minp, math_floor(skip / 2))) -- start half the sampling distance away from minp
+	local vi, ni
+
+	for y = 0, extent.y - 1, skip do
+		local sealevel = mapgen.find_nearest_lava_sealevel(minp.y + y)
+
+		if minp.y + y > sealevel then -- only create tunnels above sea level
+			for z = 0, extent.z - 1, skip do
+
+				vi = vi_offset + y * area.ystride + z * area.zstride
+				ni = z * zCaveStride + y * yCaveStride + 1
+				for x = 0, extent.x - 1, skip do
+
+					local noise = math_abs(nvals_cave[ni])
+					if noise < lowest then
+						lowest = noise
+						lowest_vi = vi
+					end
+					if noise > highest then
+						highest = noise
+						highest_vi = vi
+					end
+					ni = ni + skip
+					vi = vi + skip
+				end
+			end
+		end
+	end
+
+	if lowest < mapgen.CENTER_CAVERN_LIMIT and highest > mapgen.TCAVE + 0.03 then
+
+		local mantle_y = area:position(lowest_vi).y
+		local _, cavern_limit_distance = mapgen.find_nearest_lava_sealevel(mantle_y)
+		local _, centerRegionLimit_adj = mapgen.get_mapgenblend_adjustments(mantle_y)
+
+		 -- cavern_noise_adj gets added to noise value instead of added to the limit np_noise
+		 -- is compared against, so subtract centerRegionLimit_adj instead of adding
+		local cavern_noise_adj =
+			mapgen.CENTER_REGION_LIMIT * (cavern_limit_distance * cavern_limit_distance * cavern_limit_distance) -
+			centerRegionLimit_adj
+
+		if lowest + cavern_noise_adj < mapgen.CENTER_CAVERN_LIMIT then
+			excavate_pathway(data, area, area:position(highest_vi), area:position(lowest_vi), minp, maxp)
+			result = true
+		end
+	end
+	return result
+end
+
+
+-- an enumerated list of the different regions in the nether
+mapgen.RegionEnum = {
+	OVERWORLD     = {name = "overworld",      desc = S("The Overworld") },   -- Outside the Nether / none of the regions in the Nether
+	POSITIVE      = {name = "positive",       desc = S("Positive nether") }, -- The classic nether caverns are here - where cavePerlin > 0.6
+	POSITIVESHELL = {name = "positive shell", desc = S("Shell between positive nether and center region") }, -- the nether side of the wall/buffer area separating classic nether from the mantle
+	CENTER        = {name = "center",         desc = S("Center/Mantle, inside cavern") },
+	CENTERSHELL   = {name = "center shell",   desc = S("Center/Mantle, but outside the caverns") }, -- the mantle side of the wall/buffer area separating the positive and negative regions from the center region
+	NEGATIVE      = {name = "negative",       desc = S("Negative nether") }, -- Secondary/spare region - where cavePerlin < -0.6
+	NEGATIVESHELL = {name = "negative shell", desc = S("Shell between negative nether and center region") } -- the spare region side of the wall/buffer area separating the negative region from the mantle
+}
+
+
+-- Returns (region, noise) where region is a value from mapgen.RegionEnum
+-- and noise is the unadjusted cave perlin value
+mapgen.get_region = function(pos)
+
+	if pos.y > nether.DEPTH_CEILING or pos.y < nether.DEPTH_FLOOR then
+		return mapgen.RegionEnum.OVERWORLD, nil
+	end
+
+	local caveNoise = mapgen.get_cave_perlin_at(pos)
+	local sealevel, cavern_limit_distance = mapgen.find_nearest_lava_sealevel(pos.y)
+	local tcave_adj, centerRegionLimit_adj = mapgen.get_mapgenblend_adjustments(pos.y)
+	local tcave   = mapgen.TCAVE + tcave_adj
+	local tmantle = mapgen.CENTER_REGION_LIMIT + centerRegionLimit_adj
+
+	-- cavern_noise_adj gets added to noise value instead of added to the limit np_noise
+	-- is compared against, so subtract centerRegionLimit_adj instead of adding
+	local cavern_noise_adj =
+		mapgen.CENTER_REGION_LIMIT * (cavern_limit_distance * cavern_limit_distance * cavern_limit_distance) -
+		centerRegionLimit_adj
+
+	local region
+	if caveNoise > tcave then
+		region = mapgen.RegionEnum.POSITIVE
+	elseif -caveNoise > tcave then
+		region = mapgen.RegionEnum.NEGATIVE
+	elseif math_abs(caveNoise) < tmantle then
+
+		if math_abs(caveNoise) + cavern_noise_adj < mapgen.CENTER_CAVERN_LIMIT then
+			region = mapgen.RegionEnum.CENTER
+		else
+			region = mapgen.RegionEnum.CENTERSHELL
+		end
+
+	elseif caveNoise > 0 then
+		region = mapgen.RegionEnum.POSITIVESHELL
+	else
+		region = mapgen.RegionEnum.NEGATIVESHELL
+	end
+
+	return region, caveNoise
+end
+
+
+minetest.register_chatcommand("nether_whereami",
+	{
+		description = S("Describes which region of the nether the player is in"),
+		privs = {debug = true},
+		func = function(name, param)
+
+			local player = minetest.get_player_by_name(name)
+			if player == nil then return false, S("Unknown player position") end
+			local playerPos = vector.round(player:get_pos())
+
+			local region, caveNoise                = mapgen.get_region(playerPos)
+			local seaLevel, cavernLimitDistance    = mapgen.find_nearest_lava_sealevel(playerPos.y)
+			local tcave_adj, centerRegionLimit_adj = mapgen.get_mapgenblend_adjustments(playerPos.y)
+
+			local seaDesc = ""
+			local boundaryDesc = ""
+			local perlinDesc = ""
+
+			if region ~= mapgen.RegionEnum.OVERWORLD then
+
+				local seaPos = playerPos.y - seaLevel
+				if seaPos > 0 then
+					seaDesc = S(", @1m above lava-sea level", seaPos)
+				else
+					seaDesc = S(", @1m below lava-sea level", seaPos)
+				end
+
+				if tcave_adj > 0 then
+					boundaryDesc = S(", approaching y boundary of Nether")
+				end
+
+				perlinDesc = S("[Perlin @1] ", (math_floor(caveNoise * 1000) / 1000))
+			end
+
+			return true, S("@1@2@3@4", perlinDesc, region.desc, seaDesc, boundaryDesc)
+		end
+	}
+)

mapgen_nobiomes.lua

@@ -0,0 +1,241 @@
+--[[
+
+  Nether mod for minetest
+
+  "mapgen_nobiomes.lua" is the legacy version of the mapgen, only used
+    in older versions of Minetest or in v6 worlds.
+  "mapgen.lua" is the modern biomes-based Nether mapgen, which
+    requires Minetest v5.1 or greater
+
+
+  Copyright (C) 2013 PilzAdam
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+
+-- Parameters
+
+local NETHER_CEILING = nether.DEPTH_CEILING
+local NETHER_FLOOR   = nether.DEPTH_FLOOR
+local TCAVE = 0.6
+local BLEND = 128
+
+
+-- 3D noise
+
+local np_cave = {
+	offset = 0,
+	scale = 1,
+	spread = {x = 384, y = 128, z = 384}, -- squashed 3:1
+	seed = 59033,
+	octaves = 5,
+	persist = 0.7,
+	lacunarity = 2.0,
+	--flags = ""
+}
+
+
+-- Stuff
+
+local yblmin = NETHER_FLOOR   + BLEND * 2
+local yblmax = NETHER_CEILING - BLEND * 2
+
+
+
+-- Mapgen
+
+dofile(nether.path .. "/mapgen_decorations.lua")
+
+-- Initialize noise object, localise noise and data buffers
+
+local nobj_cave = nil
+local nbuf_cave = {}
+local dbuf = {}
+
+
+-- Content ids
+
+local c_air = minetest.get_content_id("air")
+
+--local c_stone_with_coal = minetest.get_content_id("default:stone_with_coal")
+--local c_stone_with_iron = minetest.get_content_id("default:stone_with_iron")
+local c_stone_with_mese = minetest.get_content_id("default:stone_with_mese")
+local c_stone_with_diamond = minetest.get_content_id("default:stone_with_diamond")
+local c_stone_with_gold = minetest.get_content_id("default:stone_with_gold")
+--local c_stone_with_copper = minetest.get_content_id("default:stone_with_copper")
+local c_mese = minetest.get_content_id("default:mese")
+
+local c_gravel = minetest.get_content_id("default:gravel")
+local c_dirt = minetest.get_content_id("default:dirt")
+local c_sand = minetest.get_content_id("default:sand")
+
+local c_cobble = minetest.get_content_id("default:cobble")
+local c_mossycobble = minetest.get_content_id("default:mossycobble")
+local c_stair_cobble = minetest.get_content_id("stairs:stair_cobble")
+
+local c_lava_source = minetest.get_content_id("default:lava_source")
+local c_lava_flowing = minetest.get_content_id("default:lava_flowing")
+local c_water_source = minetest.get_content_id("default:water_source")
+local c_water_flowing = minetest.get_content_id("default:water_flowing")
+
+local c_glowstone = minetest.get_content_id("nether:glowstone")
+local c_nethersand = minetest.get_content_id("nether:sand")
+local c_netherbrick = minetest.get_content_id("nether:brick")
+local c_netherrack = minetest.get_content_id("nether:rack")
+
+
+-- On-generated function
+
+minetest.register_on_generated(function(minp, maxp, seed)
+	if minp.y > NETHER_CEILING or maxp.y < NETHER_FLOOR then
+		return
+	end
+
+	local x1 = maxp.x
+	local y1 = math.min(maxp.y, NETHER_CEILING)
+	local z1 = maxp.z
+	local x0 = minp.x
+	local y0 = math.max(minp.y, NETHER_FLOOR)
+	local z0 = minp.z
+
+	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
+	local area = VoxelArea:new{MinEdge = emin, MaxEdge = emax}
+	local data = vm:get_data(dbuf)
+
+	local x11 = emax.x -- Limits of mapchunk plus mapblock shell
+	local y11 = emax.y
+	local z11 = emax.z
+	local x00 = emin.x
+	local y00 = emin.y
+	local z00 = emin.z
+
+	local ystride = x1 - x0 + 1
+	local zstride = ystride * ystride
+	local chulens = {x = ystride, y = ystride, z = ystride}
+	local minposxyz = {x = x0, y = y0, z = z0}
+
+	nobj_cave = nobj_cave or minetest.get_perlin_map(np_cave, chulens)
+	local nvals_cave = nobj_cave:get_3d_map_flat(minposxyz, nbuf_cave)
+
+	for y = y00, y11 do -- Y loop first to minimise tcave calculations
+		local tcave
+		local in_chunk_y = false
+		if y >= y0 and y <= y1 then
+			tcave = TCAVE
+			if y > yblmax then tcave = TCAVE + ((y - yblmax) / BLEND) ^ 2 end
+			if y < yblmin then tcave = TCAVE + ((yblmin - y) / BLEND) ^ 2 end
+			in_chunk_y = true
+		end
+
+		for z = z00, z11 do
+			local vi = area:index(x00, y, z) -- Initial voxelmanip index
+			local ni
+			local in_chunk_yz = in_chunk_y and z >= z0 and z <= z1
+
+			for x = x00, x11 do
+				if in_chunk_yz and x == x0 then
+					-- Initial noisemap index
+					ni = (z - z0) * zstride + (y - y0) * ystride + 1
+				end
+				local in_chunk_yzx = in_chunk_yz and x >= x0 and x <= x1 -- In mapchunk
+
+				local id = data[vi] -- Existing node
+				-- Cave air, cave liquids and dungeons are overgenerated,
+				-- convert these throughout mapchunk plus shell
+				if id == c_air or -- Air and liquids to air
+						id == c_lava_source or
+						id == c_lava_flowing or
+						id == c_water_source or
+						id == c_water_flowing then
+					data[vi] = c_air
+				-- Dungeons are preserved so we don't need
+				-- to check for cavern in the shell
+				elseif id == c_cobble or -- Dungeons (preserved) to netherbrick
+						id == c_mossycobble or
+						id == c_stair_cobble then
+					data[vi] = c_netherbrick
+				end
+
+				if in_chunk_yzx then -- In mapchunk
+					if nvals_cave[ni] > tcave then -- Only excavate cavern in mapchunk
+						data[vi] = c_air
+					elseif id == c_mese then -- Mese block to lava
+						data[vi] = c_lava_source
+					elseif id == c_stone_with_gold or -- Precious ores to glowstone
+							id == c_stone_with_mese or
+							id == c_stone_with_diamond then
+						data[vi] = c_glowstone
+					elseif id == c_gravel or -- Blob ore to nethersand
+							id == c_dirt or
+							id == c_sand then
+						data[vi] = c_nethersand
+					else -- All else to netherstone
+						data[vi] = c_netherrack
+					end
+
+					ni = ni + 1 -- Only increment noise index in mapchunk
+				end
+
+				vi = vi + 1
+			end
+		end
+	end
+
+	vm:set_data(data)
+
+	minetest.generate_decorations(vm)
+
+	vm:set_lighting({day = 0, night = 0}, minp, maxp)
+	vm:calc_lighting()
+	vm:update_liquids()
+	vm:write_to_map()
+end)
+
+
+-- use knowledge of the nether mapgen algorithm to return a suitable ground level for placing a portal.
+-- player_name is optional, allowing a player to spawn a remote portal in their own protected areas.
+function nether.find_nether_ground_y(target_x, target_z, start_y, player_name)
+	local nobj_cave_point = minetest.get_perlin(np_cave)
+	local air = 0 -- Consecutive air nodes found
+
+	local minp_schem, maxp_schem = nether.get_schematic_volume({x = target_x, y = 0, z = target_z}, nil, "nether_portal")
+	local minp = {x = minp_schem.x, y = 0, z = minp_schem.z}
+	local maxp = {x = maxp_schem.x, y = 0, z = maxp_schem.z}
+
+	for y = start_y, math.max(NETHER_FLOOR + BLEND, start_y - 4096), -1 do
+		local nval_cave = nobj_cave_point:get_3d({x = target_x, y = y, z = target_z})
+
+		if nval_cave > TCAVE then -- Cavern
+			air = air + 1
+		else -- Not cavern, check if 4 nodes of space above
+			if air >= 4 then
+				local portal_y = y + 1
+				-- Check volume for non-natural nodes
+				minp.y = minp_schem.y + portal_y
+				maxp.y = maxp_schem.y + portal_y
+				if nether.volume_is_natural_and_unprotected(minp, maxp, player_name) then
+					return portal_y
+				else -- Restart search a little lower
+					nether.find_nether_ground_y(target_x, target_z, y - 16, player_name)
+				end
+			else -- Not enough space, reset air to zero
+				air = 0
+			end
+		end
+	end
+
+	return math.max(start_y, NETHER_FLOOR + BLEND) -- Fallback
+end

mod.conf

@@ -1 +1,4 @@
 name = nether
+description = Adds a deep underground realm with different mapgen that you can reach with obsidian portals.
+depends = stairs, default
+optional_depends = toolranks, technic, moreblocks, mesecons, loot, dungeon_loot, doc_basics, fire, climate_api, ethereal, xpanes, walls

nether-compressor-recipe.lua

@@ -0,0 +1,40 @@
+local S = minetest.get_translator("nether")
+
+technic.register_recipe_type("compressing", { description = S("Compressing") })
+
+function register_compressor_recipe(data)
+	data.time = data.time or 4
+	technic.register_recipe("compressing", data)
+end
+
+local recipes = {
+	{"nether:rack",                    "nether:brick",},
+	{"nether:rack_deep",               "nether:brick_deep"},
+	{"nether:brick 9",                 "nether:brick_compressed", 12},
+	{"nether:brick_compressed 9",      "nether:nether_lump", 12}
+
+}
+-- clear craft recipe
+-- But allow brick blocks to be crafted like the other bricks from Minetest Game
+
+minetest.clear_craft({
+	recipe = {
+		{"nether:brick","nether:brick","nether:brick"},
+		{"nether:brick","nether:brick","nether:brick"},
+		{"nether:brick","nether:brick","nether:brick"},
+	}
+})
+
+minetest.clear_craft({
+	recipe = {
+		{"nether:brick_compressed","nether:brick_compressed","nether:brick_compressed"},
+		{"nether:brick_compressed","nether:brick_compressed","nether:brick_compressed"},
+		{"nether:brick_compressed","nether:brick_compressed","nether:brick_compressed"},
+	}
+})
+
+for _, data in pairs(recipes) do
+	register_compressor_recipe({input = {data[1]}, output = data[2], time = data[3]})
+end
+
+

nether_api.txt

@@ -0,0 +1,78 @@
+Modding/interop guide to Nether
+===============================
+
+For portals API see portal_api.txt
+
+The Nether mod exposes some of its functions and data via the lua global
+`nether` and `nether.mapgen`
+
+
+* `nether.DEPTH_CEILING`: [read-only] Y value of the top of the Nether.
+
+* `nether.DEPTH_FLOOR`: [read-only] Y value of the bottom of the Nether.
+
+* `nether.DEPTH_FLOOR_LAYERS`: [writable] Gives the bottom Y of all
+  locations that wish to be considered part of the Nether.
+  DEPTH_FLOOR_LAYERS Allows mods to insert extra layers below the
+  Nether, by knowing where their layer ceiling should start, and letting
+  the layers be included in effects which only happen in the Nether.
+  If a mod wishes to add a layer below the Nether it should read
+  `nether.DEPTH_FLOOR_LAYERS` to find the bottom Y of the Nether and any
+  other layers already under the Nether. The mod should leave a small gap
+  between DEPTH_FLOOR_LAYERS and its ceiling (e.g. use DEPTH_FLOOR_LAYERS - 6
+  for its ceiling Y, so there is room to shift edge-case biomes), then set
+  `nether.DEPTH_FLOOR_LAYERS` to reflect the mod's floor Y value, and call
+  `shift_existing_biomes()` with DEPTH_FLOOR_LAYERS as the `floor_y` argument.
+
+* `nether.NETHER_REALM_ENABLED`: [read-only] Gets the value of the "Enable
+  Nether realm & portal" setting the nether mod exposes in Minetest's
+  "All Settings" -> "Mods" -> "nether" options.
+  When false, the entire nether mapgen is disabled (not run), and the portal
+  to it is not registered. Reasons someone might disable the Nether realm
+  include if a nether-layer mod was to be used as the Nether instead, or if
+  the portal mechanic was desired in a game without the Nether, etc.
+
+* `nether.useBiomes`: [read-only] When this is false, the Nether interop
+  functions below are not available (nil).
+  Indicates that the biomes-enabled mapgen is in use. The Nether mod falls back
+  to older mapgen code for v6 maps and old versions of Minetest, the older
+  mapgen code doesn't use biomes and doesn't provide API/interop functions.
+
+
+Mapgen functions available when nether.useBiomes is true
+--------------------------------------------------------
+
+The following functions are nil if `nether.useBiomes` is false,
+and also nil if `nether.NETHER_REALM_ENABLED` is false.
+
+* `nether.mapgen.shift_existing_biomes(floor_y, ceiling_y)` Move any existing
+  biomes out of the y-range specified by `floor_y` and `ceiling_y`.
+
+* `nether.mapgen.get_region(pos)`: Returns two values, (region, noise) where
+  `region` is a value from `nether.mapgen.RegionEnum` and `noise` is the
+  unadjusted cave perlin value.
+    * `nether.mapgen.RegionEnum` values are tables which contain an invariant
+      `name` and a localized `desc`. Current region names include overworld,
+      positive, positive shell, center, center shell, negative, and negative
+      shell.
+      "positive" corresponds to conventional Nether caverns, and "center"
+      corresponds to the Mantle region.
+
+* `nether.mapgen.get_cave_point_perlin()`: Returns the PerlinNoise object for
+  the Nether's cavern noise.
+
+* `nether.mapgen.get_cave_perlin_at(pos)`: Returns the Nether cavern noise
+  value at a given 3D position.
+
+
+Other mapgen functions
+-------------------------------------------
+
+If the Nether realm is enabled, then this function will be available
+regardless of whether `nether.useBiomes` is true:
+
+* `nether.find_nether_ground_y(target_x, target_z, start_y, player_name)`
+  Uses knowledge of the nether mapgen algorithm to return a suitable ground
+  level for placing a portal.
+    * `player_name` is optional, allowing a player to spawn a remote portal
+      in their own protected areas.

portal_api.lua

@@ -23,8 +23,9 @@
 
 ]]--
 
-local DEBUG = false
-local DEBUG_IGNORE_MODSTORAGE = false -- setting true prevents portals from knowing where other portals are, forcing find_realm_anchorpos() etc. to be executed every time
+-- setting DEBUG_IGNORE_MODSTORAGE true prevents portals from knowing where other
+-- portals are, forcing find_realm_anchorpos() etc. to be executed every time.
+local DEBUG_IGNORE_MODSTORAGE = false
 
 nether.registered_portals = {}
 nether.registered_portals_count = 0
@@ -51,6 +52,11 @@ if minetest.get_mod_storage == nil then
 	error(nether.modname .. " does not support Minetest versions earlier than 0.4.16", 0)
 end
 
+local S = nether.get_translator
+nether.portal_destination_not_found_message =
+	S("Mysterious forces prevented you from opening that portal. Please try another location")
+
+
 --[[
 
 Positions
@@ -113,9 +119,28 @@ metadata).
 
 ]]
 
-local __ = {name = "air", prob = 0}
-local AA = {name = "air", prob = 255, force_place = true}
-local OO = {name = "default:obsidian", prob = 255, force_place = true}
+local facedir_up, facedir_north, facedir_south, facedir_east, facedir_west, facedir_down = 0, 4, 8, 12, 16, 20
+
+local __  = {name = "air", prob = 0}
+local AA  = {name = "air", prob = 255, force_place = true}
+local ON  = {name = "default:obsidian", facedir = facedir_north + 0, prob = 255, force_place = true}
+local ON2 = {name = "default:obsidian", facedir = facedir_north + 1, prob = 255, force_place = true}
+local ON3 = {name = "default:obsidian", facedir = facedir_north + 2, prob = 255, force_place = true}
+local ON4 = {name = "default:obsidian", facedir = facedir_north + 3, prob = 255, force_place = true}
+local OS  = {name = "default:obsidian", facedir = facedir_south,     prob = 255, force_place = true}
+local OE  = {name = "default:obsidian", facedir = facedir_east,      prob = 255, force_place = true}
+local OW  = {name = "default:obsidian", facedir = facedir_west,      prob = 255, force_place = true}
+local OU  = {name = "default:obsidian", facedir = facedir_up + 0,    prob = 255, force_place = true}
+local OU2 = {name = "default:obsidian", facedir = facedir_up + 1,    prob = 255, force_place = true}
+local OU3 = {name = "default:obsidian", facedir = facedir_up + 2,    prob = 255, force_place = true}
+local OU4 = {name = "default:obsidian", facedir = facedir_up + 3,    prob = 255, force_place = true}
+local OD  = {name = "default:obsidian", facedir = facedir_down,      prob = 255, force_place = true}
+
+-- facedirNodeList is a list of node references which should have their facedir value copied into
+-- param2 before placing a schematic. The facedir values will only be copied when the portal's frame
+-- node has a paramtype2 of "facedir" or "colorfacedir".
+-- Having schematics provide this list avoids needing to check every node in the schematic volume.
+local facedirNodeList = {ON, ON2, ON3, ON4, OS, OE, OW, OU, OU2, OU3, OU4, OD}
 
 -- This object defines a portal's shape, segregating the shape logic code from portal behaviour code.
 -- You can create a new "PortalShape" definition object which implements the same
@@ -285,25 +310,26 @@ nether.PortalShape_Traditional = {
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
-	
-			OO,OO,OO,OO,
-			OO,AA,AA,OO,
-			OO,AA,AA,OO,
-			OO,AA,AA,OO,
-			OO,OO,OO,OO,
-	
+
+			ON,OW,OE,ON2,
+			OU,AA,AA,OU,
+			OU,AA,AA,OU,
+			OU,AA,AA,OU,
+			ON4,OE,OW,ON3,
+
 			__,__,__,__,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
-	
+
 			__,__,__,__,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
 			AA,AA,AA,AA,
-		}
+		},
+		facedirNodes = facedirNodeList
 	}
 } -- End of PortalShape_Traditional class
 
@@ -449,7 +475,7 @@ nether.PortalShape_Circular = {
 			__,__,AA,AA,AA,__,__,
 			__,__,__,__,__,__,__,
 			__,__,__,__,__,__,__,
-	
+
 			__,__,__,__,__,__,__,
 			__,AA,AA,AA,AA,AA,__,
 			__,AA,AA,AA,AA,AA,__,
@@ -457,7 +483,7 @@ nether.PortalShape_Circular = {
 			__,AA,AA,AA,AA,AA,__,
 			__,AA,AA,AA,AA,AA,__,
 			__,__,__,__,__,__,__,
-	
+
 			__,__,__,__,__,__,__,
 			__,AA,AA,AA,AA,AA,__,
 			AA,AA,AA,AA,AA,AA,AA,
@@ -465,15 +491,15 @@ nether.PortalShape_Circular = {
 			AA,AA,AA,AA,AA,AA,AA,
 			__,AA,AA,AA,AA,AA,__,
 			__,__,AA,AA,AA,__,__,
-	
-			__,__,OO,OO,OO,__,__,
-			__,OO,AA,AA,AA,OO,__,
-			OO,AA,AA,AA,AA,AA,OO,
-			OO,AA,AA,AA,AA,AA,OO,
-			OO,AA,AA,AA,AA,AA,OO,
-			__,OO,AA,AA,AA,OO,__,
-			__,__,OO,OO,OO,__,__,
-	
+
+			__,__,OW,OW,OW,__,__,
+			__,ON,AA,AA,AA,ON2,__,
+			OU,AA,AA,AA,AA,AA,OD,
+			OU,AA,AA,AA,AA,AA,OD,
+			OU,AA,AA,AA,AA,AA,OD,
+			__,ON4,AA,AA,AA,ON3,__,
+			__,__,OE,OE,OE,__,__,
+
 			__,__,__,__,__,__,__,
 			__,AA,AA,AA,AA,AA,__,
 			AA,AA,AA,AA,AA,AA,AA,
@@ -481,7 +507,7 @@ nether.PortalShape_Circular = {
 			AA,AA,AA,AA,AA,AA,AA,
 			__,AA,AA,AA,AA,AA,__,
 			__,__,AA,AA,AA,__,__,
-	
+
 			__,__,__,__,__,__,__,
 			__,AA,AA,AA,AA,AA,__,
 			__,AA,AA,AA,AA,AA,__,
@@ -497,7 +523,8 @@ nether.PortalShape_Circular = {
 			__,__,AA,AA,AA,__,__,
 			__,__,__,__,__,__,__,
 			__,__,__,__,__,__,__,
-		}
+		},
+		facedirNodes = facedirNodeList
 	}
 } -- End of PortalShape_Circular class
 
@@ -597,35 +624,36 @@ nether.PortalShape_Platform = {
 		size = {x = 5, y = 5, z = 5},
 		data = { -- note that data is upside down
 			__,__,__,__,__,
-			OO,OO,OO,OO,OO,
+			OU4,OW,OW,OW,OU3,
 			__,AA,AA,AA,__,
 			__,AA,AA,AA,__,
 			__,__,__,__,__,
-	
-			__,OO,OO,OO,__,
-			OO,AA,AA,AA,OO,
+
+			__,OU4,OW,OU3,__,
+			ON,AA,AA,AA,OS,
 			AA,AA,AA,AA,AA,
 			AA,AA,AA,AA,AA,
 			__,AA,AA,AA,__,
-	
-			__,OO,OO,OO,__,
-			OO,AA,AA,AA,OO,
+
+			__,ON,OD,OS,__,
+			ON,AA,AA,AA,OS,
 			AA,AA,AA,AA,AA,
 			AA,AA,AA,AA,AA,
 			__,AA,AA,AA,__,
-	
-			__,OO,OO,OO,__,
-			OO,AA,AA,AA,OO,
+
+			__,OU,OE,OU2,__,
+			ON,AA,AA,AA,OS,
 			AA,AA,AA,AA,AA,
 			AA,AA,AA,AA,AA,
 			__,AA,AA,AA,__,
-	
+
 			__,__,__,__,__,
-			OO,OO,OO,OO,OO,
+			OU,OE,OE,OE,OU2,
 			__,AA,AA,AA,__,
 			__,AA,AA,AA,__,
 			__,__,__,__,__,
-		}
+		},
+		facedirNodes = facedirNodeList
 	}
 } -- End of PortalShape_Platform class
 
@@ -640,8 +668,8 @@ nether.PortalShape_Platform = {
 -- Portal implementation functions --
 -- =============================== --
 
+local debugf = nether.debug
 local ignition_item_name
-local S = nether.get_translator
 local mod_storage = minetest.get_mod_storage()
 local meseconsAvailable = minetest.get_modpath("mesecon") ~= nil and minetest.global_exists("mesecon")
 local book_added_as_treasure = false
@@ -799,7 +827,7 @@ end
 local function store_portal_location_info(portal_name, anchorPos, orientation, ignited)
 	if not DEBUG_IGNORE_MODSTORAGE then
 		local key = minetest.pos_to_string(anchorPos) .. " is " .. portal_name
-		if DEBUG then minetest.chat_send_all("Adding/updating portal in mod_storage: " .. key) end
+		debugf("Adding/updating portal in mod_storage: " .. key)
 		mod_storage:set_string(
 			key,
 			minetest.serialize({orientation = orientation, active = ignited})
@@ -812,7 +840,7 @@ end
 local function remove_portal_location_info(portal_name, anchorPos)
 	if not DEBUG_IGNORE_MODSTORAGE then
 		local key = minetest.pos_to_string(anchorPos) .. " is " .. portal_name
-		if DEBUG then minetest.chat_send_all("Removing portal from mod_storage: " .. key) end
+		debugf("Removing portal from mod_storage: " .. key)
 		mod_storage:set_string(key, "")
 	end
 end
@@ -850,7 +878,7 @@ local function list_closest_portals(portal_definition, anchorPos, distance_limit
 						local distance = math.hypot(y * y_factor, math.hypot(x, z))
 						if distance <= distance_limit or distance_limit < 0 then
 							local info = minetest.deserialize(value) or {}
-							if DEBUG then minetest.chat_send_all("found " .. found_name .. " listed at distance " .. distance ..  " (within " .. distance_limit .. ") from dest " .. minetest.pos_to_string(anchorPos) .. ", found: " .. minetest.pos_to_string(found_anchorPos) .. " orientation " .. info.orientation) end
+							debugf("found %s listed at distance %.2f (within %.2f) from dest %s, found: %s orientation %s", found_name, distance, distance_limit, anchorPos, found_anchorPos, info.orientation)
 							info.anchorPos = found_anchorPos
 							info.distance  = distance
 							result[distance] = info
@@ -902,14 +930,14 @@ end
 function extinguish_portal(pos, node_name, frame_was_destroyed)
 
 	-- mesecons seems to invoke action_off() 6 times every time you place a block?
-	if DEBUG then minetest.chat_send_all("extinguish_portal" .. minetest.pos_to_string(pos) .. " " .. node_name) end
+	debugf("extinguish_portal %s %s", pos, node_name)
 
 	local meta = minetest.get_meta(pos)
 	local p1 = minetest.string_to_pos(meta:get_string("p1"))
 	local p2 = minetest.string_to_pos(meta:get_string("p2"))
 	local target = minetest.string_to_pos(meta:get_string("target"))
 	if p1 == nil or p2 == nil then
-		if DEBUG then minetest.chat_send_all("    no active portal found to extinguish") end
+		debugf("    no active portal found to extinguish")
 		return false
 	end
 
@@ -961,7 +989,7 @@ function extinguish_portal(pos, node_name, frame_was_destroyed)
 	end
 
 	if target ~= nil then
-		if DEBUG then minetest.chat_send_all("    attempting to also extinguish target with wormholePos " .. minetest.pos_to_string(target)) end
+		debugf("    attempting to also extinguish target with wormholePos %s", target)
 		extinguish_portal(target, node_name)
 	end
 
@@ -978,7 +1006,8 @@ end
 -- Note: will extinguish any portal using the same nodes that are being set
 local function set_portal_metadata(portal_definition, anchorPos, orientation, destination_wormholePos, ignite)
 
-	if DEBUG then minetest.chat_send_all("set_portal_metadata(ignite=" .. tostring(ignite) .. ") at " .. minetest.pos_to_string(anchorPos) .. " orient " .. orientation .. ", setting to target " .. minetest.pos_to_string(destination_wormholePos)) end
+	ignite = ignite or false;
+	debugf("set_portal_metadata(ignite=%s) at %s orient %s, setting to target %s", ignite, anchorPos, orientation, destination_wormholePos)
 
 	-- Portal position is stored in metadata as p1 and p2 to keep maps compatible with earlier versions of this mod.
 	-- p1 is the bottom/west/south corner of the portal, and p2 is the opposite corner, together
@@ -1006,7 +1035,7 @@ local function set_portal_metadata(portal_definition, anchorPos, orientation, de
 			if existing_p1 ~= "" then
 				local existing_p2 = meta:get_string("p2")
 				if existing_p1 ~= p1_string or existing_p2 ~= p2_string then
-					if DEBUG then minetest.chat_send_all("set_portal_metadata() found existing metadata from another portal: existing_p1 " .. existing_p1 .. ", existing_p2" .. existing_p2 .. ", p1 " .. p1_string .. ", p2 " .. p2_string .. ", will existinguish existing portal...") end
+					debugf("set_portal_metadata() found existing metadata from another portal: existing_p1 %s, existing_p2 %s, p1 %s, p2 %s, will extinguish existing portal...", existing_p1, existing_p2, p1_string, p2_string)
 					-- this node is already part of another portal, so extinguish that, because nodes only
 					-- contain a link in the metadata to one portal, and being part of two allows a slew of bugs
 					extinguish_portal(pos, node_name, false)
@@ -1070,7 +1099,7 @@ local function is_portal_at_anchorPos(portal_definition, anchorPos, orientation,
 				-- area isn't loaded, force loading/emerge of check area
 				minetest.get_voxel_manip():read_from_map(check_pos, check_pos)
 				foundName = minetest.get_node(check_pos).name
-				if DEBUG then minetest.chat_send_all("Forced loading of 'ignore' node at " .. minetest.pos_to_string(check_pos) .. ", got " .. foundName) end
+				debugf("Forced loading of 'ignore' node at %s, got %s", check_pos, foundName)
 
 				if foundName ~= frame_node_name then
 					nodes_are_valid = false
@@ -1137,8 +1166,29 @@ local function is_within_portal_frame(portal_definition, pos)
 end
 
 
+-- sets param2 values in the schematic to match facedir values, or 0 if the portalframe-nodedef doesn't use facedir
+local function set_schematic_param2(schematic_table, frame_node_name, frame_node_color)
+
+	local paramtype2 = minetest.registered_nodes[frame_node_name].paramtype2
+	local isFacedir = paramtype2 == "facedir" or paramtype2 == "colorfacedir"
+
+	if schematic_table.facedirNodes ~= nil then
+		for _, node in ipairs(schematic_table.facedirNodes) do
+			if isFacedir and node.facedir ~= nil then
+				-- frame_node_color can be nil
+				local colorBits = (frame_node_color or math.floor((node.param2 or 0) / 32)) * 32
+				node.param2 = node.facedir + colorBits
+			else
+				node.param2 = 0
+			end
+		end
+	end
+end
+
 local function build_portal(portal_definition, anchorPos, orientation, destination_wormholePos)
 
+	set_schematic_param2(portal_definition.shape.schematic, portal_definition.frame_node_name, portal_definition.frame_node_color)
+
 	minetest.place_schematic(
 		portal_definition.shape.get_schematicPos_from_anchorPos(anchorPos, orientation),
 		portal_definition.shape.schematic,
@@ -1159,7 +1209,7 @@ local function build_portal(portal_definition, anchorPos, orientation, destinati
 		function(pos) minetest.swap_node(pos, wormholeNode) end
 	)
 
-	if DEBUG then minetest.chat_send_all("Placed " .. portal_definition.name .. " portal schematic at " ..  minetest.pos_to_string(portal_definition.shape.get_schematicPos_from_anchorPos(anchorPos, orientation)) .. ", orientation " .. orientation) end
+	debugf("Placed %s portal schematic at %s, orientation %s", portal_definition.name, portal_definition.shape.get_schematicPos_from_anchorPos(anchorPos, orientation), orientation)
 
 	set_portal_metadata(portal_definition, anchorPos, orientation, destination_wormholePos)
 
@@ -1173,13 +1223,13 @@ end
 -- Make portals immortal for ~20 seconds after creation
 local function remote_portal_checkup(elapsed, portal_definition, anchorPos, orientation, destination_wormholePos)
 
-	if DEBUG then minetest.chat_send_all("portal checkup at " .. elapsed .. " seconds") end
+	debugf("portal checkup at %d seconds", elapsed)
 
 	local wormholePos = portal_definition.shape.get_wormholePos_from_anchorPos(anchorPos, orientation)
 	local wormhole_node = minetest.get_node_or_nil(wormholePos)
 
-	local portalFound, portalLit = false, false	
-	if wormhole_node ~= nil and wormhole_node.name == portal_definition.wormhole_node_name then 
+	local portalFound, portalLit = false, false
+	if wormhole_node ~= nil and wormhole_node.name == portal_definition.wormhole_node_name then
 		-- a wormhole node was there, but check the whole frame is intact
 		portalFound, portalLit = is_portal_at_anchorPos(portal_definition, anchorPos, orientation, false)
 	end
@@ -1188,7 +1238,7 @@ local function remote_portal_checkup(elapsed, portal_definition, anchorPos, orie
 		-- ruh roh
 		local message = "Newly created portal at " .. minetest.pos_to_string(anchorPos) .. " was overwritten. Attempting to recreate. Issue spotted after " .. elapsed .. " seconds"
 		minetest.log("warning", message)
-		if DEBUG then minetest.chat_send_all("!!! " .. message) end
+		debugf("!!! " .. message)
 
 		-- A pre-existing portal frame wouldn't have been immediately overwritten, so no need to check for one, just place the portal.
 		build_portal(portal_definition, anchorPos, orientation, destination_wormholePos)
@@ -1216,7 +1266,7 @@ end
 -- specified if an existing portal was already found there.
 local function locate_or_build_portal(portal_definition, suggested_wormholePos, suggested_orientation, destination_wormholePos)
 
-	if DEBUG then minetest.chat_send_all("locate_or_build_portal() called at wormholePos" .. minetest.pos_to_string(suggested_wormholePos) .. " with suggested orient " .. suggested_orientation .. ", targetted to " .. minetest.pos_to_string(destination_wormholePos)) end
+	debugf("locate_or_build_portal() called at wormholePos%s with suggested orient %s, targeted to %s", suggested_wormholePos, suggested_orientation, destination_wormholePos)
 
 	local result_anchorPos;
 	local result_orientation;
@@ -1237,13 +1287,13 @@ local function locate_or_build_portal(portal_definition, suggested_wormholePos,
 			if result_target ~= nil and vector.equals(result_target, destination_wormholePos) then
 				-- It already links back to the portal the player is teleporting from, so don't
 				-- extinguish it or the player's portal will also extinguish.
-				if DEBUG then minetest.chat_send_all("    Build unnecessary: already a lit portal that links back here at " ..  minetest.pos_to_string(found_anchorPos) .. ", orientation " .. result_orientation) end
+				debugf("    Build unnecessary: already a lit portal that links back here at %s, orientation %s", found_anchorPos, result_orientation)
 			else
-				if DEBUG then minetest.chat_send_all("    Build unnecessary: already a lit portal at " ..  minetest.pos_to_string(found_anchorPos) .. ", orientation " .. result_orientation .. ", linking to " .. result_target_str .. ". Extinguishing...") end
+				debugf("    Build unnecessary: already a lit portal at %s, orientation %s, linking to %s. Extinguishing...", found_anchorPos, result_orientation, result_target_str)
 				extinguish_portal(found_anchorPos, portal_definition.frame_node_name, false)
 			end
 		else
-			if DEBUG then minetest.chat_send_all("    Build unnecessary: already an unlit portal at " ..  minetest.pos_to_string(found_anchorPos) .. ", orientation " .. result_orientation) end
+			debugf("    Build unnecessary: already an unlit portal at %s, orientation %s", found_anchorPos, result_orientation)
 		end
 		-- ignite the portal
 		set_portal_metadata_and_ignite(portal_definition, result_anchorPos, result_orientation, destination_wormholePos)
@@ -1260,11 +1310,12 @@ end
 
 
 -- invoked when a player attempts to turn obsidian nodes into an open portal
+-- player_name is optional, allowing a player to spawn a remote portal in their own protected area
 -- ignition_node_name is optional
-local function ignite_portal(ignition_pos, ignition_node_name)
+local function ignite_portal(ignition_pos, player_name, ignition_node_name)
 
 	if ignition_node_name == nil then ignition_node_name = minetest.get_node(ignition_pos).name end
-	if DEBUG then minetest.chat_send_all("IGNITE the " .. ignition_node_name .. " at " .. minetest.pos_to_string(ignition_pos)) end
+	debugf("IGNITE the %s at %s", ignition_node_name, ignition_pos)
 
 	-- find which sort of portals are made from the node that was clicked on
 	local portal_definition_list = list_portal_definitions_for_frame_node(ignition_node_name)
@@ -1275,7 +1326,7 @@ local function ignite_portal(ignition_pos, ignition_node_name)
 		-- check it was a portal frame that the player is trying to ignite
 		local anchorPos, orientation, is_ignited = is_within_portal_frame(portal_definition, ignition_pos)
 		if anchorPos == nil then
-			if DEBUG then minetest.chat_send_all("No " .. portal_definition.name .. " portal frame found at " .. minetest.pos_to_string(ignition_pos)) end
+			debugf("No %s portal frame found at ", portal_definition.name, ignition_pos)
 			continue = true -- no portal is here, but perhaps there's more than one portal type we need to search for
 		elseif is_ignited then
 			-- Found a portal, check its metadata and timer is healthy.
@@ -1287,10 +1338,10 @@ local function ignite_portal(ignition_pos, ignition_node_name)
 					-- metadata is missing, the portal frame node must have been removed without calling
 					-- on_destruct - perhaps by an ABM, then replaced - presumably by a player.
 					-- allowing reigniting will repair the portal
-					if DEBUG then minetest.chat_send_all("Broken portal detected, allowing reignition/repair") end
+					debugf("Broken portal detected, allowing reignition/repair")
 					repair = true
 				else
-					if DEBUG then minetest.chat_send_all("This portal links to " .. meta:get_string("target") .. ". p1=" .. meta:get_string("p1") .. " p2=" .. meta:get_string("p2")) end
+					debugf("This portal links to %s. p1=%s p2=%s", meta:get_string("target"), meta:get_string("p1"), meta:get_string("p2"))
 
 					-- Check the portal's timer is running, and fix if it's not.
 					-- A portal's timer can stop running if the game is played without that portal type being
@@ -1298,7 +1349,7 @@ local function ignite_portal(ignition_pos, ignition_node_name)
 					-- (if this is a frequent problem, then change the value of "run_at_every_load" in the lbm)
 					local timer = minetest.get_node_timer(get_timerPos_from_p1_and_p2(minetest.string_to_pos(p1), minetest.string_to_pos(p2)))
 					if timer ~= nil and timer:get_timeout() == 0 then
-						if DEBUG then minetest.chat_send_all("Portal timer was not running: restarting the timer.") end
+						debugf("Portal timer was not running: restarting the timer.")
 						timer:start(1)
 					end
 				end
@@ -1307,23 +1358,30 @@ local function ignite_portal(ignition_pos, ignition_node_name)
 		end
 
 		if continue == false then
-			if DEBUG then minetest.chat_send_all("Found portal frame. Looked at " .. minetest.pos_to_string(ignition_pos) .. ", found at " .. minetest.pos_to_string(anchorPos) .. " orientation " .. orientation) end
+			debugf("Found portal frame. Looked at %s, found at %s orientation %s", ignition_pos, anchorPos, orientation)
 
 			local destination_anchorPos, destination_orientation
 			if portal_definition.is_within_realm(ignition_pos) then
-				destination_anchorPos, destination_orientation = portal_definition.find_surface_anchorPos(anchorPos)
+				destination_anchorPos, destination_orientation = portal_definition.find_surface_anchorPos(anchorPos, player_name or "")
 			else
-				destination_anchorPos, destination_orientation = portal_definition.find_realm_anchorPos(anchorPos)
+				destination_anchorPos, destination_orientation = portal_definition.find_realm_anchorPos(anchorPos, player_name or "")
+			end
+			if destination_orientation == nil then
+				debugf("No destination_orientation given")
+				destination_orientation = orientation
 			end
-			if DEBUG and destination_orientation == nil then minetest.chat_send_all("No destination_orientation given") end
-			if destination_orientation == nil then destination_orientation = orientation end
 
-			if destination_anchorPos == nil then
-				if DEBUG then minetest.chat_send_all("No portal destination available here!") end
+			if destination_anchorPos == nil or destination_anchorPos.y == nil then
+				-- destination_anchorPos.y was also checked for nil in case portal_definition.find_surface_anchorPos()
+				-- had used nether.find_surface_target_y() and that had returned nil.
+				debugf("No portal destination available here!")
+				if (player_name or "") ~= "" then
+					minetest.chat_send_player(player_name, nether.portal_destination_not_found_message)
+				end
 				return false
 			else
 				local destination_wormholePos = portal_definition.shape.get_wormholePos_from_anchorPos(destination_anchorPos, destination_orientation)
-				if DEBUG then minetest.chat_send_all("Destination set to " .. minetest.pos_to_string(destination_anchorPos)) end
+				debugf("Destination set to %s", destination_anchorPos)
 
 				-- ignition/BURN_BABY_BURN
 				set_portal_metadata_and_ignite(portal_definition, anchorPos, orientation, destination_wormholePos)
@@ -1362,7 +1420,7 @@ local function ensure_remote_portal_then_teleport(playerName, portal_definition,
 	local local_p1, local_p2 = portal_definition.shape:get_p1_and_p2_from_anchorPos(local_anchorPos, local_orientation)
 	local p1_at_playerPos = minetest.string_to_pos(meta:get_string("p1"))
 	if p1_at_playerPos == nil or not vector.equals(local_p1, p1_at_playerPos) then
-		if DEBUG then minetest.chat_send_all("the player already teleported from " .. minetest.pos_to_string(local_anchorPos) .. ", and is now standing in a different portal - " .. meta:get_string("p1")) end
+		debugf("the player already teleported from %s, and is now standing in a different portal - %s", local_anchorPos, meta:get_string("p1"))
 		return -- the player already teleported, and is now standing in a different portal
 	end
 
@@ -1370,7 +1428,7 @@ local function ensure_remote_portal_then_teleport(playerName, portal_definition,
 
 	if dest_wormhole_node == nil then
 		-- area not emerged yet, delay and retry
-		if DEBUG then minetest.chat_send_all("ensure_remote_portal_then_teleport() could not find anything yet at " .. minetest.pos_to_string(destination_wormholePos)) end
+		debugf("ensure_remote_portal_then_teleport() could not find anything yet at %s", destination_wormholePos)
 		minetest.after(1, ensure_remote_portal_then_teleport, playerName, portal_definition, local_anchorPos, local_orientation, destination_wormholePos)
 	else
 		local local_wormholePos = portal_definition.shape.get_wormholePos_from_anchorPos(local_anchorPos, local_orientation)
@@ -1387,9 +1445,9 @@ local function ensure_remote_portal_then_teleport(playerName, portal_definition,
 			local remoteMeta = minetest.get_meta(destination_wormholePos)
 			local remoteTarget = minetest.string_to_pos(remoteMeta:get_string("target"))
 			if remoteTarget == nil then
-				if DEBUG then minetest.chat_send_all("Failed to test whether target portal links back to this one") end
+				debugf("Failed to test whether target portal links back to this one")
 			elseif not vector.equals(remoteTarget, local_wormholePos) then
-				if DEBUG then minetest.chat_send_all("Target portal is already linked, extinguishing then relighting to point back at this one") end
+				debugf("Target portal is already linked, extinguishing then relighting to point back at this one")
 				extinguish_portal(remoteTarget, portal_definition.frame_node_name, false)
 				set_portal_metadata_and_ignite(
 					portal_definition,
@@ -1399,7 +1457,7 @@ local function ensure_remote_portal_then_teleport(playerName, portal_definition,
 				)
 			end
 
-			if DEBUG then minetest.chat_send_all("Teleporting player from wormholePos" .. minetest.pos_to_string(local_wormholePos) .. " to wormholePos" .. minetest.pos_to_string(destination_wormholePos)) end
+			debugf("Teleporting player from wormholePos%s to wormholePos%s", local_wormholePos, destination_wormholePos)
 
 			-- play the teleport sound
 			if portal_definition.sounds.teleport ~= nil then
@@ -1426,7 +1484,7 @@ local function ensure_remote_portal_then_teleport(playerName, portal_definition,
 			--   which will leave a confused player.
 			--   I don't think this is worth preventing, but I document it incase someone describes entering a portal
 			--   and then the portal turning off.
-			if DEBUG then minetest.chat_send_all("ensure_remote_portal_then_teleport() saw " .. dest_wormhole_node.name .. " at " .. minetest.pos_to_string(destination_wormholePos) .. " rather than a wormhole. Calling locate_or_build_portal()") end
+			debugf("ensure_remote_portal_then_teleport() saw %s at %s rather than a wormhole. Calling locate_or_build_portal()", dest_wormhole_node.name, destination_wormholePos)
 
 			local new_dest_anchorPos, new_dest_orientation = locate_or_build_portal(portal_definition, destination_wormholePos, local_orientation, local_wormholePos)
 			local new_dest_wormholePos = portal_definition.shape.get_wormholePos_from_anchorPos(new_dest_anchorPos, new_dest_orientation)
@@ -1443,10 +1501,10 @@ local function ensure_remote_portal_then_teleport(playerName, portal_definition,
 					-- local portal to also be extinguished.
 					local message = "Local portal at " .. minetest.pos_to_string(local_anchorPos) .. " was extinguished while linking to existing portal at " .. minetest.pos_to_string(new_dest_anchorPos)
 					minetest.log("error", message)
-					if DEBUG then minetest.chat_send_all("!ERROR! - " .. message) end
+					debugf("!ERROR! - " .. message)
 				else
 					destination_wormholePos = new_dest_wormholePos
-					if DEBUG then minetest.chat_send_all("    updating target to where remote portal was found - " .. minetest.pos_to_string(destination_wormholePos)) end
+					debugf("    updating target to where remote portal was found - %s", destination_wormholePos)
 
 					set_portal_metadata(
 						portal_definition,
@@ -1722,7 +1780,7 @@ local function create_book_of_portals()
 		ignition_item_description = minetest.registered_items[ignition_item_name].description
 	end
 	intro_text = intro_text ..
-		S("\n\nThe key to opening such a doorway is to strike the frame with a @1, at which point the very air inside begins to crackle and glow.", string.lower(ignition_item_description))
+		S("\n\nThe key to opening such a doorway is to strike the frame with a @1, at which point the very air inside begins to crackle and glow.", ignition_item_description)
 
 	chapters[#chapters + 1] = {text = intro_text}
 
@@ -1781,22 +1839,22 @@ function register_frame_node(frame_node_name)
 	extended_node_def.replaced_by_portalapi.mesecons = extended_node_def.mesecons
 	extended_node_def.mesecons = {effector = {
 		action_on = function (pos, node)
-			if DEBUG then minetest.chat_send_all("portal frame material: mesecons action ON") end
-			ignite_portal(pos, node.name)
+			debugf("portal frame material: mesecons action ON")
+			ignite_portal(pos, nil, node.name)
 		end,
 		action_off = function (pos, node)
-			if DEBUG then minetest.chat_send_all("portal frame material: mesecons action OFF") end
+			debugf("portal frame material: mesecons action OFF")
 			extinguish_portal(pos, node.name, false)
 		end
 	}}
 	extended_node_def.replaced_by_portalapi.on_destruct = extended_node_def.on_destruct
 	extended_node_def.on_destruct = function(pos)
-		if DEBUG then minetest.chat_send_all("portal frame material: destruct") end
+		debugf("portal frame material: destruct")
 		extinguish_portal(pos, frame_node_name, true)
 	end
 	extended_node_def.replaced_by_portalapi.on_blast = extended_node_def.on_blast
 	extended_node_def.on_blast = function(pos, intensity)
-		if DEBUG then minetest.chat_send_all("portal frame material: blast") end
+		debugf("portal frame material: blast")
 		extinguish_portal(pos, frame_node_name, extended_node_def.replaced_by_portalapi.on_blast == nil)
 		if extended_node_def.replaced_by_portalapi.on_blast ~= nil then
 			extended_node_def.replaced_by_portalapi.on_blast(pos, intensity)
@@ -1864,6 +1922,10 @@ function test_portaldef_is_valid(portal_definition)
 	assert(portal_definition.wormhole_node_color >= 0 and portal_definition.wormhole_node_color < 8, "portaldef.wormhole_node_color must be between 0 and 7 (inclusive)")
 	assert(portal_definition.is_within_realm      ~= nil, "portaldef.is_within_realm() must be implemented")
 	assert(portal_definition.find_realm_anchorPos ~= nil, "portaldef.find_realm_anchorPos() must be implemented")
+
+	if portal_definition.frame_node_color ~= nil then
+		assert(portal_definition.frame_node_color >= 0 and portal_definition.frame_node_color < 8, "portal_definition.frame_node_color must be between 0 and 7 (inclusive)")
+	end
 	-- todo
 
 	return result
@@ -1888,9 +1950,9 @@ minetest.register_lbm({
 			local timer = minetest.get_node_timer(timerPos)
 			if timer ~= nil then
 				timer:start(1)
-				if DEBUG then minetest.chat_send_all("LBM started portal timer " .. minetest.pos_to_string(timerPos)) end
-			elseif DEBUG then
-				minetest.chat_send_all("get_node_timer" .. minetest.pos_to_string(timerPos) .. " returned null")
+				debugf("LBM started portal timer %s", timerPos)
+			else
+				debugf("get_node_timer%s returned null", timerPos)
 			end
 		end
 	end
@@ -1916,7 +1978,7 @@ local wormhole_nodedef_default = {
 				type = "vertical_frames",
 				aspect_w = 16,
 				aspect_h = 16,
-				length = 0.5,
+				length = 0.9,
 			},
 		},
 		{
@@ -1925,7 +1987,7 @@ local wormhole_nodedef_default = {
 				type = "vertical_frames",
 				aspect_w = 16,
 				aspect_h = 16,
-				length = 0.5,
+				length = 0.9,
 			},
 		},
 	},
@@ -1945,7 +2007,8 @@ local wormhole_nodedef_default = {
 		a = 160, r = 128, g = 0, b = 80
 	},
 	sunlight_propagates = true,
-	use_texture_alpha = true,
+	use_texture_alpha = minetest.features.use_texture_alpha_string_modes
+		and "blend" or true,
 	walkable = false,
 	diggable = false,
 	pointable = false,
@@ -1953,7 +2016,6 @@ local wormhole_nodedef_default = {
 	is_ground_content = false,
 	drop = "",
 	light_source = 5,
-	alpha = 192,
 	node_box = {
 		type = "fixed",
 		fixed = {
@@ -2011,7 +2073,7 @@ function nether.register_portal(name, portaldef)
 	end
 
 	portaldef.name     = name
-	portaldef.mod_name = minetest.get_current_modname()
+	portaldef.mod_name = minetest.get_current_modname() or "<mod name not recorded>"
 
 	-- use portaldef_default for any values missing from portaldef or portaldef.sounds
 	if portaldef.sounds ~= nil then setmetatable(portaldef.sounds, {__index = portaldef_default.sounds}) end
@@ -2034,7 +2096,7 @@ function nether.register_portal(name, portaldef)
 	end
 
 	if portaldef.find_surface_anchorPos == nil then	-- default to using find_surface_target_y()
-		portaldef.find_surface_anchorPos = function(pos)
+		portaldef.find_surface_anchorPos = function(pos, player_name)
 
 			local destination_pos = {x = pos.x, y = 0, z = pos.z}
 			local existing_portal_location, existing_portal_orientation =
@@ -2042,7 +2104,7 @@ function nether.register_portal(name, portaldef)
 			if existing_portal_location ~= nil then
 				return existing_portal_location, existing_portal_orientation
 			else
-				destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, name)
+				destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, name, player_name)
 				return destination_pos
 			end
 		end
@@ -2104,22 +2166,20 @@ function nether.unregister_portal(name)
 end
 
 function nether.register_portal_ignition_item(item_name, ignition_failure_sound)
-
+	local old_on_place = minetest.registered_items[item_name].on_place or minetest.item_place
 	minetest.override_item(item_name, {
-		on_place = function(stack, _, pt)
-			local done = false
+		on_place = function(stack, placer, pt, ...)
 			if pt.under and nether.is_frame_node[minetest.get_node(pt.under).name] then
-				done = ignite_portal(pt.under)
+				local done = ignite_portal(pt.under, placer:get_player_name())
 				if done and not minetest.settings:get_bool("creative_mode") then
 					stack:take_item()
 				end
+				if not done and ignition_failure_sound ~= nil then
+					minetest.sound_play(ignition_failure_sound, {pos = pt.under, max_hear_distance = 10})
+				end
+				return stack
 			end
-			if not done and ignition_failure_sound ~= nil then
-				minetest.sound_play(ignition_failure_sound, {pos = pt.under, max_hear_distance = 10})
-			end
-
-
-			return stack
+			return old_on_place(stack, placer, pt, ...)
 		end,
 	})
 
@@ -2128,32 +2188,32 @@ end
 
 -- use this when determining where to spawn a portal, to avoid overwriting player builds
 -- It checks the area for any nodes that aren't ground or trees.
+-- player_name is optional, allowing a player to spawn a remote portal in their own protected areas.
 -- (Water also fails this test, unless it is unemerged)
-function nether.volume_is_natural(minp, maxp)
+function nether.volume_is_natural_and_unprotected(minp, maxp, player_name)
+
 	local c_air = minetest.get_content_id("air")
 	local c_ignore = minetest.get_content_id("ignore")
 
 	local vm = minetest.get_voxel_manip()
-	local pos1 = {x = minp.x, y = minp.y, z = minp.z}
-	local pos2 = {x = maxp.x, y = maxp.y, z = maxp.z}
-	local emin, emax = vm:read_from_map(pos1, pos2)
+	local emin, emax = vm:read_from_map(minp, maxp)
 	local area = VoxelArea:new({MinEdge = emin, MaxEdge = emax})
 	local data = vm:get_data()
 
-	for z = pos1.z, pos2.z do
-	for y = pos1.y, pos2.y do
-		local vi = area:index(pos1.x, y, z)
-		for x = pos1.x, pos2.x do
+	for z = minp.z, maxp.z do
+	for y = minp.y, maxp.y do
+		local vi = area:index(minp.x, y, z)
+		for x = minp.x, maxp.x do
 			local id = data[vi] -- Existing node
-			if DEBUG and id == nil then minetest.chat_send_all("nil block at index " .. vi) end
+			if id == nil then debugf("nil block at index " .. vi) end
 			if id ~= c_air and id ~= c_ignore and id ~= nil then -- checked for common natural or not emerged
 				local name = minetest.get_name_from_content_id(id)
 				local nodedef = minetest.registered_nodes[name]
-				if not nodedef.is_ground_content then
+				if nodedef and not nodedef.is_ground_content then
 					-- trees are natural but not "ground content"
 					local node_groups = nodedef.groups
 					if node_groups == nil or (node_groups.tree == nil and node_groups.leaves == nil and node_groups.leafdecay == nil) then
-						if DEBUG then minetest.chat_send_all("volume_is_natural() found unnatural node " .. name) end
+						debugf("volume_is_natural_and_unprotected() found unnatural node %s", name)
 						return false
 					end
 				end
@@ -2163,13 +2223,73 @@ function nether.volume_is_natural(minp, maxp)
 	end
 	end
 
-	if DEBUG then minetest.chat_send_all("Volume is natural") end
+	if minetest.is_area_protected(minp, maxp, player_name or "") then
+		debugf("Volume is protected against player '%s', %s-%s", player_name, minp, maxp)
+		return false;
+	end
+
+	debugf("Volume is natural and unprotected for player '%s', %s-%s", player_name, minp, maxp)
 	return true
 end
 
+-- Deprecated, use nether.volume_is_natural_and_unprotected() instead.
+function nether.volume_is_natural(minp, maxp)
+
+	if nether.deprecation_warning_volume_is_natural == nil then
+		local stack = debug.traceback("", 2);
+		local calling_func = (string.split(stack, "\n", false, 2, false)[2] or ""):trim()
+		minetest.log("warning",
+			"Deprecated function \"nether.volume_is_natural()\" invoked, use \"nether.volume_is_natural_and_unprotected()\" instead. " ..
+			calling_func)
+		nether.deprecation_warning_volume_is_natural = true;
+	end
+
+	return nether.volume_is_natural_and_unprotected(minp, maxp)
+end
+
+-- Gets the volume that may be altered if a portal is placed at the anchor_pos
+-- orientation is optional, but specifying it will reduce the volume returned
+-- portal_name is optional, but specifying it will reduce the volume returned
+-- returns minp, maxp
+function nether.get_schematic_volume(anchor_pos, orientation, portal_name)
+
+	if orientation == nil then
+		-- Return a volume large enough for any orientation
+		local minp0, maxp0 = nether.get_schematic_volume(anchor_pos, 0, portal_name)
+		local minp1, maxp1 = nether.get_schematic_volume(anchor_pos, 1, portal_name)
+
+		-- ToDo: If an asymmetric portal is used with an anchor not at the center of the
+		-- schematic then we will also need to check orientations 3 and 4.
+		-- (The currently existing portal-shapes are not affected)
+		return
+			{x = math.min(minp0.x, minp1.x), y = math.min(minp0.y, minp1.y), z = math.min(minp0.z, minp1.z)},
+			{x = math.max(maxp0.x, maxp1.x), y = math.max(maxp0.y, maxp1.y), z = math.max(maxp0.z, maxp1.z)}
+	end
+
+	-- Assume the largest possible portal shape unless we know it's a smaller one.
+	local shape_defintion = nether.PortalShape_Circular
+	if portal_name ~= nil and nether.registered_portals[portal_name] ~= nil then
+		shape_defintion = nether.registered_portals[portal_name].shape
+	end
+
+	local size = shape_defintion.schematic.size
+	local minp = shape_defintion.get_schematicPos_from_anchorPos(anchor_pos, orientation);
+	local maxp
+
+	if (orientation % 2) == 0 then
+		maxp = {x = minp.x + size.x - 1, y = minp.y + size.y - 1, z = minp.z + size.z - 1}
+	else
+		maxp = {x = minp.x + size.z - 1, y = minp.y + size.y - 1, z = minp.z + size.x - 1}
+	end
+	return minp, maxp
+end
+
+
 -- Can be used when implementing custom find_surface_anchorPos() functions
--- portal_name is optional, providing it allows existing portals on the surface to be reused.
-function nether.find_surface_target_y(target_x, target_z, portal_name)
+-- portal_name is optional, providing it allows existing portals on the surface to be reused, and
+-- a potentially smaller volume to be checked by volume_is_natural_and_unprotected().
+-- player_name is optional, allowing a player to spawn a remote portal in their own protected areas.
+function nether.find_surface_target_y(target_x, target_z, portal_name, player_name)
 
 	assert(target_x ~= nil and target_z ~= nil, "Arguments `target_x` and `target_z` cannot be nil when calling find_surface_target_y()")
 
@@ -2199,24 +2319,35 @@ function nether.find_surface_target_y(target_x, target_z, portal_name)
 		end
 	end
 
-	for y = start_y, start_y - 256, -16 do
+	local minp_schem, maxp_schem = nether.get_schematic_volume({x = target_x, y = 0, z = target_z}, nil, portal_name)
+	local minp = {x = minp_schem.x, y = 0, z = minp_schem.z}
+	local maxp = {x = maxp_schem.x, y = 0, z = maxp_schem.z}
+
+	-- Starting searchstep at -16 and making it larger by 2 after each step gives a 20-step search range down to -646:
+	-- 0, -16, -34, -54, -76, -100, -126, -154, -184, -216, -250, -286, -324, -364, -406, -450, -496, -544, -594, -646
+	local searchstep = -16;
+
+	local y = start_y
+	while y > start_y - 650 do
 		-- Check volume for non-natural nodes
-		local minp = {x = target_x - 1, y = y - 1, z = target_z - 2}
-		local maxp = {x = target_x + 2, y = y + 3, z = target_z + 2}
-		if nether.volume_is_natural(minp, maxp) then
+		minp.y = minp_schem.y + y
+		maxp.y = maxp_schem.y + y
+		if nether.volume_is_natural_and_unprotected(minp, maxp, player_name) then
 			return y
 		elseif portal_name ~= nil and nether.registered_portals[portal_name] ~= nil then
 			-- players have built here - don't grief.
 			-- but reigniting existing portals in portal rooms is fine - desirable even.
 			local anchorPos, orientation, is_ignited = is_within_portal_frame(nether.registered_portals[portal_name], {x = target_x, y = y, z = target_z})
 			if anchorPos ~= nil then
-				if DEBUG then minetest.chat_send_all("Volume_is_natural check failed, but a portal frame is here " .. minetest.pos_to_string(anchorPos) .. ", so this is still a good target y level") end
+				debugf("volume_is_natural_and_unprotected check failed, but a portal frame is here %s, so this is still a good target y level", anchorPos)
 				return y
 			end
 		end
+		y = y + searchstep
+		searchstep = searchstep - 2
 	end
 
-	return start_y - 256 -- Fallback
+	return nil -- Portal ignition failure. Possibly due to a large protected area.
 end
 
 
@@ -2239,7 +2370,7 @@ function nether.find_nearest_working_portal(portal_name, anchorPos, distance_lim
 
 	for _, dist in ipairs(dist_list) do
 		local portal_info = contenders[dist]
-		if DEBUG then minetest.chat_send_all("checking portal from mod_storage at " .. minetest.pos_to_string(portal_info.anchorPos) .. " orientation " .. portal_info.orientation) end
+		debugf("checking portal from mod_storage at %s orientation %s", portal_info.anchorPos, portal_info.orientation)
 
 		-- the mod_storage list of portals is unreliable - e.g. it won't know if inactive portals have been
 		-- destroyed, so check the portal is still there
@@ -2248,10 +2379,11 @@ function nether.find_nearest_working_portal(portal_name, anchorPos, distance_lim
 		if portalFound then
 			return portal_info.anchorPos, portal_info.orientation
 		else
-			if DEBUG then minetest.chat_send_all("Portal wasn't found, removing portal from mod_storage at " .. minetest.pos_to_string(portal_info.anchorPos) .. " orientation " .. portal_info.orientation) end
+			debugf("Portal wasn't found, removing portal from mod_storage at %s orientation %s",
+				portal_info.anchorPos, portal_info.orientation)
 			-- The portal at that location must have been destroyed
 			remove_portal_location_info(portal_name, portal_info.anchorPos)
 		end
 	end
 	return nil
-end
+end

portal_api.txt

@@ -22,6 +22,9 @@ one kind of portal with the same frame material — such as obsidian — provide
 the size of the PortalShape is distinct from any other type of portal that is
 using the same node for its frame, and portal sizes remain small.
 
+The Nether provides three variants of Nether basalt to ensure there are
+alternatives to obsidian for other mods to use as portalstones.
+
 
 Realms
 ------
@@ -49,17 +52,24 @@ surface.
 Helper functions
 ----------------
 
-* `nether.volume_is_natural(minp, maxp)`: returns a boolean
+* `nether.volume_is_natural_and_unprotected(minp, maxp, player_name)`: returns
+  a boolean.
     * use this when determining where to spawn a portal, to avoid overwriting
       player builds. It checks the area for any nodes that aren't ground or
       trees.
       Water will fail this test, unless it is unemerged.
+    * player_name is optional, providing it allows the player's own protected
+      areas to be treated as unprotected.
 
-* `nether.find_surface_target_y(target_x, target_z, portal_name)`: returns a
-  suitable anchorPos
+* `nether.find_surface_target_y(target_x, target_z, portal_name, player_name)`:
+  returns a suitable anchorPos
     * Can be used when implementing custom find_surface_anchorPos() functions
     * portal_name is optional, providing it allows existing portals on the
       surface to be reused.
+    * player_name is optional, providing it prevents the exclusion of surface
+      target areas which are protected by the player.
+    * May return nil in extreme circumstances, such as the surface being
+      protected down to a great depth.
 
 * `nether.find_nearest_working_portal(portal_name, anchorPos, distance_limit, y_factor)`: returns
   (anchorPos, orientation), or nil if no portal was found within the
@@ -115,6 +125,12 @@ Used by `nether.register_portal`.
         -- Required. For best results, have your portal constructed of a
         -- material nobody else is using.
 
+        frame_node_color = 0,
+        -- Optional.
+        -- A value from 0 to 7. Only used if the frame node's paramtype2 is
+        -- "colorfacedir", in which case this color will be used when a remote
+        -- portal is created.
+
         shape = nether.PortalShape_Traditional,
         -- Optional.
         -- Shapes available are:
@@ -127,6 +143,9 @@ Used by `nether.register_portal`.
         -- Optional. Allows a custom wormhole node to be specified.
         -- Useful if you want the portals to have a different post_effect_color
         -- or texture.
+        -- The Nether mod provides:
+        --     "nether:portal" (default)
+        --     "nether:portal_alt"
 
         wormhole_node_color = 0,
         -- Optional. Defaults to 0/magenta.
@@ -199,7 +218,7 @@ Used by `nether.register_portal`.
         -- Ideally implementations are fast, as this function can be used to
         -- sift through a list of portals.
 
-        find_realm_anchorPos = function(surface_anchorPos),
+        find_realm_anchorPos = function(surface_anchorPos, player_name),
         -- Required. Return a position in the realm that a portal created at
         -- surface_anchorPos will link to.
         -- Return an anchorPos or (anchorPos, orientation)
@@ -208,8 +227,12 @@ Used by `nether.register_portal`.
         -- If the location of an existing portal is returned then include the
         -- orientation, otherwise the existing portal could be overwritten by
         -- a new one with the orientation of the surface portal.
+        -- Return nil, or a position with a nil y component, to prevent the
+        -- portal from igniting.
+        -- player_name may be "", e.g. if the portal was ignited by a mesecon,
+        -- and is provided for use with volume_is_natural_and_unprotected() etc.
 
-        find_surface_anchorPos = function(realm_anchorPos),
+        find_surface_anchorPos = function(realm_anchorPos, player_name),
         -- Optional. If you don't implement this then a position near the
         -- surface will be picked.
         -- Return an anchorPos or (anchorPos, orientation)
@@ -222,17 +245,21 @@ Used by `nether.register_portal`.
         -- If the location of an existing portal is returned then include the
         -- orientation, otherwise the existing portal could be overwritten by
         -- a new one with the orientation of the realm portal.
+        -- Return nil, or a position with a nil y component, to prevent the
+        -- portal from igniting.
+        -- player_name may be "", e.g. if the portal was ignited by a mesecon,
+        -- and is provided for use with volume_is_natural_and_unprotected() etc.
 
-        on_run_wormhole      = function(portalDef, anochorPos, orientation),
+        on_run_wormhole      = function(portalDef, anchorPos, orientation),
         -- invoked once per second per portal
-        on_extinguish        = function(portalDef, anochorPos, orientation),
+        on_extinguish        = function(portalDef, anchorPos, orientation),
         -- invoked when a portal is extinguished, including when the portal
         -- it connected to was extinguished.
         on_player_teleported = function(portalDef, player, oldPos, newPos),
         -- invoked immediately after a player is teleported
-        on_ignite            = function(portalDef, anochorPos, orientation)
+        on_ignite            = function(portalDef, anchorPos, orientation)
         -- invoked when a player or mesecon ignites a portal
-        on_created           = function(portalDef, anochorPos, orientation)
+        on_created           = function(portalDef, anchorPos, orientation)
         -- invoked when a portal creates a remote twin, this is usually when
         -- a player travels through a portal for the first time.
     }

portal_examples.lua

@@ -85,7 +85,7 @@ This portal is different to the others, rather than acting akin to a doorway it
 			return pos.y > FLOATLAND_LEVEL - 200
 		end,
 
-		find_realm_anchorPos = function(surface_anchorPos)
+		find_realm_anchorPos = function(surface_anchorPos, player_name)
 			-- TODO: Once paramat finishes adjusting the floatlands, implement a surface algorithm that finds land
 			local destination_pos = {x = surface_anchorPos.x ,y = FLOATLAND_LEVEL + 2, z = surface_anchorPos.z}
 
@@ -106,7 +106,7 @@ end
 -- Surface-travel portal, playable code example --
 --==============================================--
 
--- These Moore Curve functions requred by surface_portal's find_surface_anchorPos() will
+-- These Moore Curve functions required by surface_portal's find_surface_anchorPos() will
 -- be assigned later in this file.
 local get_moore_distance -- will be function get_moore_distance(cell_count, x, y): integer
 local get_moore_coords   -- will be function get_moore_coords(cell_count, distance): pos2d
@@ -116,6 +116,7 @@ if minetest.settings:get_bool("nether_enable_portal_example_surfacetravel", ENAB
 	nether.register_portal("surface_portal", {
 		shape               = nether.PortalShape_Circular,
 		frame_node_name     = "default:tinblock",
+		wormhole_node_name  = "nether:portal_alt",
 		wormhole_node_color = 4, -- 4 is cyan
 		title = S("Surface Portal"),
 		book_of_portals_pagetext = S([[Requiring 16 blocks of tin and constructed in a circular fashion, a finished frame is seven blocks wide, seven blocks high, and stands vertically like a doorway.
@@ -130,13 +131,13 @@ Due to such difficulties, we never learned what determines the direction and dis
 			return true
 		end,
 
-		find_realm_anchorPos = function(surface_anchorPos)
+		find_realm_anchorPos = function(surface_anchorPos, player_name)
 			-- This function isn't needed, since this type of portal always goes to the surface
 			minetest.log("error" , "find_realm_anchorPos called for surface portal")
 			return {x=0, y=0, z=0}
 		end,
 
-		find_surface_anchorPos = function(realm_anchorPos)
+		find_surface_anchorPos = function(realm_anchorPos, player_name)
 			-- A portal definition doesn't normally need to provide a find_surface_anchorPos() function,
 			-- since find_surface_target_y() will be used by default, but these portals travel around the
 			-- surface (following a Moore curve) so will be calculating a different x and z to realm_anchorPos.
@@ -191,7 +192,7 @@ Due to such difficulties, we never learned what determines the direction and dis
 				end
 
 				local destination_pos = {x = target_x + adj_x, y = 0, z = target_z + adj_z}
-				destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, "surface_portal")
+				destination_pos.y = nether.find_surface_target_y(destination_pos.x, destination_pos.z, "surface_portal", player_name)
 
 				return destination_pos
 			end

settingtypes.txt

@@ -16,4 +16,10 @@ nether_realm_enabled (Enable Nether realm & portal) bool true
 nether_enable_portal_example_floatlands (Enable example portal: Floatlands) bool false
 
 # Enables the Surface-travel portal api code example
-nether_enable_portal_example_surfacetravel (Enable example portal: Surface-travel) bool false
+nether_enable_portal_example_surfacetravel (Enable example portal: Surface-travel) bool false
+
+[Nether depth]
+#The depth where the Nether begins / the Nether ceiling
+nether_depth_ymax (Upper limit of Nether) int -5000 -30000 32767
+#The lower limit of the Nether must be at least 1000 lower than the upper limit, and more than 3000 lower is recommended.
+nether_depth_ymin (Lower limit of Nether) int -11000 -32768 30000

tools.lua

@@ -0,0 +1,394 @@
+--[[
+
+  Copyright (C) 2020 lortas
+
+  Permission to use, copy, modify, and/or distribute this software for
+  any purpose with or without fee is hereby granted, provided that the
+  above copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR
+  BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES
+  OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+  SOFTWARE.
+
+]]--
+
+local S = nether.get_translator
+
+minetest.register_tool("nether:pick_nether", {
+	description = S("Nether Pickaxe\nWell suited for mining netherrack"),
+	_doc_items_longdesc = S("Uniquely suited for mining netherrack, with minimal wear when doing so. Blunts quickly on other materials."),
+	inventory_image = "nether_tool_netherpick.png",
+	tool_capabilities = {
+		full_punch_interval = 0.8,
+		max_drop_level=3,
+		groupcaps={
+			cracky = {times={[1]=1.90, [2]=0.9, [3]=0.3}, uses=35, maxlevel=2},
+		},
+		damage_groups = {fleshy=4},
+	},
+	sound = {breaks = "default_tool_breaks"},
+	groups = {pickaxe = 1},
+
+	after_use = function(itemstack, user, node, digparams)
+		local wearDivisor = 1
+		local nodeDef = minetest.registered_nodes[node.name]
+		if nodeDef ~= nil and nodeDef.groups ~= nil then
+			-- The nether pick hardly wears out when mining netherrack
+			local workable = nodeDef.groups.workable_with_nether_tools or 0
+			wearDivisor =  1 + (3 * workable) -- 10 for netherrack, 1 otherwise. Making it able to mine 350 netherrack nodes, instead of 35.
+		end
+
+		local wear = math.floor(digparams.wear / wearDivisor)
+		itemstack:add_wear(wear)  -- apply the adjusted wear as usual
+		return itemstack
+	end
+})
+
+minetest.register_tool("nether:shovel_nether", {
+	description = S("Nether Shovel"),
+	inventory_image = "nether_tool_nethershovel.png",
+	wield_image = "nether_tool_nethershovel.png^[transformR90",
+	tool_capabilities = {
+		full_punch_interval = 1.0,
+		max_drop_level=3,
+		groupcaps={
+			crumbly = {times={[1]=1.0, [2]=0.4, [3]=0.25}, uses=35, maxlevel=3},
+		},
+		damage_groups = {fleshy=4},
+	},
+	sound = {breaks = "default_tool_breaks"},
+	groups = {shovel = 1}
+})
+
+minetest.register_tool("nether:axe_nether", {
+	description = S("Nether Axe"),
+	inventory_image = "nether_tool_netheraxe.png",
+	tool_capabilities = {
+		full_punch_interval = 0.8,
+		max_drop_level=1,
+		groupcaps={
+			choppy={times={[1]=1.9, [2]=0.7, [3]=0.4}, uses=35, maxlevel=3},
+		},
+		damage_groups = {fleshy=7},
+	},
+	sound = {breaks = "default_tool_breaks"},
+	groups = {axe = 1}
+})
+
+minetest.register_tool("nether:sword_nether", {
+	description = S("Nether Sword"),
+	inventory_image = "nether_tool_nethersword.png",
+	tool_capabilities = {
+		full_punch_interval = 0.7,
+		max_drop_level=1,
+		groupcaps={
+			snappy={times={[1]=1.5, [2]=0.6, [3]=0.2}, uses=45, maxlevel=3},
+		},
+		damage_groups = {fleshy=10},
+	},
+	sound = {breaks = "default_tool_breaks"},
+	groups = {sword = 1}
+})
+
+minetest.register_craftitem("nether:nether_ingot", {
+	description = S("Nether Ingot"),
+	inventory_image = "nether_nether_ingot.png"
+})
+minetest.register_craftitem("nether:nether_lump", {
+	description = S("Nether Lump"),
+	inventory_image = "nether_nether_lump.png",
+})
+
+minetest.register_craft({
+	type = "cooking",
+	output = "nether:nether_ingot",
+	recipe = "nether:nether_lump",
+	cooktime = 30,
+})
+minetest.register_craft({
+	output = "nether:nether_lump",
+	recipe = {
+		{"nether:brick_compressed","nether:brick_compressed","nether:brick_compressed"},
+		{"nether:brick_compressed","nether:brick_compressed","nether:brick_compressed"},
+		{"nether:brick_compressed","nether:brick_compressed","nether:brick_compressed"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:pick_nether",
+	recipe = {
+		{"nether:nether_ingot","nether:nether_ingot","nether:nether_ingot"},
+		{"", "group:stick", ""},
+		{"", "group:stick", ""}
+	}
+})
+minetest.register_craft({
+	output = "nether:shovel_nether",
+	recipe = {
+		{"nether:nether_ingot"},
+		{"group:stick"},
+		{"group:stick"}
+	}
+})
+minetest.register_craft({
+	output = "nether:axe_nether",
+	recipe = {
+		{"nether:nether_ingot","nether:nether_ingot"},
+		{"nether:nether_ingot","group:stick"},
+		{"","group:stick"}
+	}
+})
+minetest.register_craft({
+	output = "nether:sword_nether",
+	recipe = {
+		{"nether:nether_ingot"},
+		{"nether:nether_ingot"},
+		{"group:stick"}
+	}
+})
+
+
+if minetest.get_modpath("toolranks") then
+
+	local function add_toolranks(name)
+		local nethertool_after_use = ItemStack(name):get_definition().after_use
+		toolranks.add_tool(name)
+		local toolranks_after_use  = ItemStack(name):get_definition().after_use
+
+		if nethertool_after_use == nil or nethertool_after_use == toolranks_after_use then
+			return
+		end
+
+		minetest.override_item(name, {
+			after_use = function(itemstack, user, node, digparams)
+				-- combine nethertool_after_use and toolranks_after_use by allowing
+				-- nethertool_after_use() to calculate the wear...
+				local initial_wear = itemstack:get_wear()
+				itemstack = nethertool_after_use(itemstack, user, node, digparams)
+				local wear = itemstack:get_wear() - initial_wear
+				itemstack:set_wear(initial_wear) -- restore/undo the wear
+
+				-- ...and have toolranks_after_use() apply the wear.
+				digparams.wear = wear
+				return toolranks_after_use(itemstack, user, node, digparams)
+			end
+		})
+	end
+
+	add_toolranks("nether:pick_nether")
+	add_toolranks("nether:shovel_nether")
+	add_toolranks("nether:axe_nether")
+	add_toolranks("nether:sword_nether")
+end
+
+
+--===========================--
+--== Nether Staff of Light ==--
+--===========================--
+
+nether.lightstaff_recipes = {
+	["nether:rack"]                 = "nether:glowstone",
+	["nether:brick"]                = "nether:glowstone",
+	["nether:brick_cracked"]        = "nether:glowstone",
+	["nether:brick_compressed"]     = "nether:glowstone",
+	["stairs:slab_netherrack"]      = "nether:glowstone",
+	["nether:rack_deep"]            = "nether:glowstone_deep",
+	["nether:brick_deep"]           = "nether:glowstone_deep",
+	["stairs:slab_netherrack_deep"] = "nether:glowstone_deep"
+}
+nether.lightstaff_range    = 100
+nether.lightstaff_velocity = 60
+nether.lightstaff_gravity  = 0  -- using 0 instead of 10 because projectile arcs look less magical - magic isn't affected by gravity ;) (but set this to 10 if you're making a crossbow etc.)
+nether.lightstaff_uses     = 60 -- number of times the Eternal Lightstaff can be used before wearing out
+nether.lightstaff_duration = 40 -- lifespan of glowstone created by the termporay Lightstaff
+
+-- 'serverLag' is a rough amount to reduce the projected impact-time the server must wait before initiating the
+-- impact events (i.e. node changing to glowstone with explosion particle effect).
+-- In tests using https://github.com/jagt/clumsy to simulate network lag I've found this value to not noticeably
+-- matter. A large network lag is noticeable in the time between clicking fire and when the shooting-particleEffect
+-- begins, as well as the time between when the impact sound/particleEffect start and when the netherrack turns
+-- into glowstone. The synchronization that 'serverLag' adjusts seems to already tolerate network lag well enough (at
+-- least when lag is consistent, as I have not simulated random lag)
+local serverLag = 0.05 -- in seconds. Larger values makes impact events more premature/early.
+
+-- returns a pointed_thing, or nil if no solid node intersected the ray
+local function raycastForSolidNode(rayStartPos, rayEndPos)
+
+	local raycast = minetest.raycast(
+		rayStartPos,
+		rayEndPos,
+		false, -- objects - if false, only nodes will be returned. Default is `true`
+		true   -- liquids - if false, liquid nodes won't be returned. Default is `false`
+	)
+	local next_pointed = raycast:next()
+	while next_pointed do
+		local under_node = minetest.get_node(next_pointed.under)
+		local under_def = minetest.registered_nodes[under_node.name]
+
+		if (under_def and not under_def.buildable_to) or not under_def then
+			return next_pointed
+		end
+
+		next_pointed  = raycast:next(next_pointed)
+	end
+	return nil
+end
+
+-- Turns a node into a light source
+-- `lightDuration` 0 is considered permanent, lightDuration is in seconds
+-- returns true if a node is transmogrified into a glowstone
+local function light_node(pos, playerName, lightDuration)
+
+	local result = false
+	if minetest.is_protected(pos, playerName) then
+		minetest.record_protection_violation(pos, playerName)
+		return false
+	end
+
+	local oldNode = minetest.get_node(pos)
+	local litNodeName = nether.lightstaff_recipes[oldNode.name]
+
+	if litNodeName ~= nil then
+		result = nether.magicallyTransmogrify_node(
+			pos,
+			playerName,
+			{name=litNodeName},
+			{name = "nether_rack_destroy", gain = 0.8},
+			lightDuration == 0 -- isPermanent
+		)
+
+		if lightDuration > 0 then
+			minetest.after(lightDuration,
+				function()
+					-- Restore the node to its original type.
+					--
+					-- If the server crashes or shuts down before this is invoked, the node
+					-- will remain in its transmogrified state. These could be cleaned up
+					-- with an LBM, but I don't think that's necessary: if this functionality
+					-- is only being used for the Nether Lightstaff then I don't think it
+					-- matters if there's occasionally an extra glowstone left in the
+					-- netherrack.
+					nether.magicallyTransmogrify_node(pos, playerName)
+				end
+			)
+		end
+	end
+	return result
+end
+
+-- a lightDuration of 0 is considered permanent, lightDuration is in seconds
+-- returns true if a node is transmogrified into a glowstone
+local function lightstaff_on_use(user, boltColorString, lightDuration)
+
+	if not user then return false end
+	local playerName    = user:get_player_name()
+	local playerlookDir = user:get_look_dir()
+	local playerPos     = user:get_pos()
+	local playerEyePos  = vector.add(playerPos, {x = 0, y = 1.5, z = 0}) -- not always the cameraPos, e.g. 3rd person mode.
+	local target        = vector.add(playerEyePos, vector.multiply(playerlookDir, nether.lightstaff_range))
+
+	local targetHitPos  = nil
+	local targetNodePos = nil
+	local target_pointed = raycastForSolidNode(playerEyePos, target)
+	if target_pointed then
+		targetNodePos = target_pointed.under
+		targetHitPos = vector.divide(vector.add(target_pointed.under, target_pointed.above), 2)
+	end
+
+	local wieldOffset = {x= 0.5, y = -0.2, z= 0.8}
+	local lookRotation =  ({x = -user:get_look_vertical(), y = user:get_look_horizontal(), z = 0})
+	local wieldPos = vector.add(playerEyePos, vector.rotate(wieldOffset, lookRotation))
+	local aimPos = targetHitPos or target
+	local distance = math.abs(vector.length(vector.subtract(aimPos, wieldPos)))
+	local flightTime = distance / nether.lightstaff_velocity
+	local dropDistance = nether.lightstaff_gravity * 0.5 * (flightTime * flightTime)
+	aimPos.y = aimPos.y + dropDistance
+	local boltDir = vector.normalize(vector.subtract(aimPos, wieldPos))
+
+	minetest.sound_play("nether_lightstaff", {to_player = playerName, gain = 0.8}, true)
+
+	-- animate a "magic bolt" from wieldPos to aimPos
+	local particleSpawnDef = {
+		amount = 20,
+		time = 0.4,
+		minpos = vector.add(wieldPos, -0.13),
+		maxpos = vector.add(wieldPos,  0.13),
+		minvel = vector.multiply(boltDir, nether.lightstaff_velocity - 0.3),
+		maxvel = vector.multiply(boltDir, nether.lightstaff_velocity + 0.3),
+		minacc = {x=0, y=-nether.lightstaff_gravity, z=0},
+		maxacc = {x=0, y=-nether.lightstaff_gravity, z=0},
+		minexptime = 1,
+		maxexptime = 2,
+		minsize = 4,
+		maxsize = 5,
+		collisiondetection = true,
+		collision_removal = true,
+		texture = "nether_particle_anim3.png",
+		animation = { type = "vertical_frames", aspect_w = 7, aspect_h = 7, length = 0.8 },
+		glow = 15
+	}
+	minetest.add_particlespawner(particleSpawnDef)
+	particleSpawnDef.texture = "nether_particle_anim3.png^[colorize:" .. boltColorString .. ":alpha"
+	particleSpawnDef.amount  = 12
+	particleSpawnDef.time    = 0.2
+	particleSpawnDef.minsize = 6
+	particleSpawnDef.maxsize = 7
+	particleSpawnDef.minpos  = vector.add(wieldPos, -0.35)
+	particleSpawnDef.maxpos  = vector.add(wieldPos,  0.35)
+	minetest.add_particlespawner(particleSpawnDef)
+
+	local result = false
+	if targetNodePos then
+		-- delay the impact until roughly when the particle effects will have reached the target
+		minetest.after(
+			math.max(0, (distance / nether.lightstaff_velocity) - serverLag),
+			function()
+				light_node(targetNodePos, playerName, lightDuration)
+			end
+		)
+
+		if lightDuration ~= 0 then
+			-- we don't need to care whether the transmogrify will be successful
+			result = true
+		else
+			-- check whether the transmogrify will be successful
+			local targetNode = minetest.get_node(targetNodePos)
+			result = nether.lightstaff_recipes[targetNode.name] ~= nil
+		end
+	end
+	return result
+end
+
+-- Inspired by FaceDeer's torch crossbow and Xanthin's Staff of Light
+minetest.register_tool("nether:lightstaff", {
+	description = S("Nether staff of Light\nTemporarily transforms the netherrack into glowstone"),
+	inventory_image = "nether_lightstaff.png",
+	wield_image     = "nether_lightstaff.png",
+	light_source = 11, -- used by wielded_light mod etc.
+	stack_max = 1,
+	on_use = function(itemstack, user, pointed_thing)
+		lightstaff_on_use(user, "#F70", nether.lightstaff_duration)
+	end
+})
+
+minetest.register_tool("nether:lightstaff_eternal", {
+	description = S("Nether staff of Eternal Light\nCreates glowstone from netherrack"),
+	inventory_image = "nether_lightstaff.png^[colorize:#55F:90",
+	wield_image     = "nether_lightstaff.png^[colorize:#55F:90",
+	light_source = 11, -- used by wielded_light mod etc.
+	sound = {breaks = "default_tool_breaks"},
+	stack_max = 1,
+	on_use = function(itemstack, user, pointed_thing)
+		if lightstaff_on_use(user, "#23F", 0) then -- was "#8088FF" or "#13F"
+			-- The staff of Eternal Light wears out, to limit how much
+			-- a player can alter the nether with it.
+			itemstack:add_wear(65535 / (nether.lightstaff_uses - 1))
+		end
+		return itemstack
+	end
+})