Update README.md

Adds a magma oceans region to the nether outside the existing nether caverns, which can be reached via tunnels.

Other misc changes:
* chatcomment nether_whereami, a debug aid for knowing which perlin-noise region you are in
* Nether ores no longer obtainable on the ceiling
* Move crafts into crafts.lua
* Add steam to lava cooling, and play bubbling lava upon death by lava
* Add cracked netherbrick
    a decorative node which can only be obtained from dungeons or structures
    I encourage someone to improve or replace the cracked netherbrick texture. For copyright purposes it's currently a derivative work (by me, 2020) from nether_brick.png, which is licensed under CC BY-SA 3.0 by PilzAdam, so it can fall under the "All other media" PilzAdam's credit in readme.md rather than need its own entry.

.luacheckrc

@@ -1,18 +1,29 @@
 unused_args = false
 allow_defined_top = true
 
+globals = {
+	"nether"
+}
+
 read_globals = {
 	"core",
 	"default",
 	"DIR_DELIM",
 	"dump",
+	"dungeon_loot",
 	"intllib",
 	"ItemStack",
+	"loot",
+	"doc",
+	"math.hypot",
+	"mesecon",
 	"minetest",
 	"nodeupdate",
+	"PcgRandom",
 	"PseudoRandom",
 	"stairs",
 	"stairsplus",
+	"string.split",
 	table = { fields = { "copy", "getn" } },
 	"vector",
 	"VoxelArea",

README.md

@@ -1,4 +1,32 @@
-Nether Mod for Minetest
+# 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.
+
+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
+
+Nether Portals can allow surface fast-travel.
+
 
 ## License of source code:
 
@@ -17,15 +45,33 @@ 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.
 
-## License of media (textures and sounds)
+## License and attribution of media (textures and sounds)
 
-Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)
-http://creativecommons.org/licenses/by-sa/3.0/
+### [Public Domain Dedication (CC0 1.0)](https://creativecommons.org/publicdomain/zero/1.0/)
 
-## Authors of media files
+ * `nether_portal_teleport.ogg` is a timing adjusted version of "teleport" by [outroelison](https://freesound.org/people/outroelison), used under CC0 1.0
 
-Everything not listed in here:
-Copyright (C) 2013 PilzAdam
+### [Attribution 3.0 Unported (CC BY 3.0)](https://creativecommons.org/licenses/by/3.0/)
 
- - nether_rack.png: Zeg9
- - nether_glowstone.png: BlockMen
+ * `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.
+
+### [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_fumarole.ogg`: Treer, 2020
+ * `nether_lava_bubble`* (files starting with "nether_lava_bubble"): Treer, 2020
+ * `nether_lava_crust_animated.png`: Treer, 2019-2020
+ * `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_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.

crafts.lua

@@ -0,0 +1,64 @@
+--[[
+
+  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: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

@@ -1,3 +1,8 @@
-stairs
 default
+stairs
+doc_basics?
+dungeon_loot?
+fire?
+loot?
+mesecons?
 moreblocks?

init.lua

@@ -1,4 +1,3 @@
-
 --[[
 
   Nether mod for minetest
@@ -20,690 +19,227 @@
 
 ]]--
 
+-- 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
 
--- Parameters
-
-local NETHER_DEPTH = -5000
-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 yblmax = NETHER_DEPTH - BLEND * 2
-
-
--- Functions
-
-local function build_portal(pos, target)
-	local p1 = {x = pos.x - 1, y = pos.y - 1, z = pos.z}
-	local p2 = {x = p1.x + 3, y = p1.y + 4, z = p1.z}
-
-	local path = minetest.get_modpath("nether") .. "/schematics/nether_portal.mts"
-	minetest.place_schematic({x = p1.x, y = p1.y, z = p1.z - 2}, path, 0, nil, true)
-
-	for y = p1.y, p2.y do
-	for x = p1.x, p2.x do
-		local meta = minetest.get_meta({x = x, y = y, z = p1.z})
-		meta:set_string("p1", minetest.pos_to_string(p1))
-		meta:set_string("p2", minetest.pos_to_string(p2))
-		meta:set_string("target", minetest.pos_to_string(target))
-	end
+local S
+if minetest.get_translator ~= nil then
+	S = minetest.get_translator("nether")
+else
+	-- mock the translator function for MT 0.4
+	S = function(str, ...)
+		local args={...}
+		return str:gsub(
+			"@%d+",
+			function(match) return args[tonumber(match:sub(2))]	end
+		)
 	end
 end
 
+-- Global Nether namespace
+nether                = {}
+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
 
-local function volume_is_natural(minp, maxp)
-	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 area = VoxelArea:new({MinEdge = emin, MaxEdge = emax})
-	local data = vm:get_data()
+-- Settings
+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
 
-	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
-			local id = data[vi] -- Existing node
-			if id ~= c_air and id ~= c_ignore then -- These are natural
-				local name = minetest.get_name_from_content_id(id)
-				if not minetest.registered_nodes[name].is_ground_content then
-					return false
-				end
-			end
-			vi = vi + 1
-		end
-	end
-	end
 
-	return true
+-- 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)
+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.
 
 
-local function find_nether_target_y(target_x, target_z, start_y)
-	local nobj_cave_point = minetest.get_perlin(np_cave)
-	local air = 0 -- Consecutive air nodes found
+-- 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, ...)
 
-	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 args = {...}
+	local argCount = select("#", ...)
 
-		if nval_cave > TCAVE then -- Cavern
-			air = air + 1
-		else -- Not cavern, check if 4 nodes of space above
-			if air >= 4 then
-				-- 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 volume_is_natural(minp, maxp) then
-					return y + 2
-				else -- Restart search a little lower
-					find_nether_target_y(target_x, target_z, y - 16)
-				end
-			else -- Not enough space, reset air to zero
-				air = 0
+	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
 
-	return start_y -- Fallback
+	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
 
 
-local function find_surface_target_y(target_x, target_z, start_y)
-	for y = start_y, start_y - 256, -16 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 volume_is_natural(minp, maxp) then
-			return y
-		end
-	end
-
-	return start_y - 256 -- Fallback
-end
-
-
-local function move_check(p1, max, dir)
-	local p = {x = p1.x, y = p1.y, z = p1.z}
-	local d = math.abs(max - p1[dir]) / (max - p1[dir])
-
-	while p[dir] ~= max do
-		p[dir] = p[dir] + d
-		if minetest.get_node(p).name ~= "default:obsidian" then
-			return false
-		end
-	end
-
-	return true
-end
-
-
-local function check_portal(p1, p2)
-	if p1.x ~= p2.x then
-		if not move_check(p1, p2.x, "x") then
-			return false
-		end
-		if not move_check(p2, p1.x, "x") then
-			return false
-		end
-	elseif p1.z ~= p2.z then
-		if not move_check(p1, p2.z, "z") then
-			return false
-		end
-		if not move_check(p2, p1.z, "z") then
-			return false
-		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
+	if nether.useBiomes then
+		dofile(nether.path .. "/mapgen.lua")
 	else
-		return false
-	end
-
-	if not move_check(p1, p2.y, "y") then
-		return false
-	end
-	if not move_check(p2, p1.y, "y") then
-		return false
-	end
-
-	return true
-end
-
-
-local function is_portal(pos)
-	for d = -3, 3 do
-		for y = -4, 4 do
-			local px = {x = pos.x + d, y = pos.y + y, z = pos.z}
-			local pz = {x = pos.x, y = pos.y + y, z = pos.z + d}
-
-			if check_portal(px, {x = px.x + 3, y = px.y + 4, z = px.z}) then
-				return px, {x = px.x + 3, y = px.y + 4, z = px.z}
-			end
-			if check_portal(pz, {x = pz.x, y = pz.y + 4, z = pz.z + 3}) then
-				return pz, {x = pz.x, y = pz.y + 4, z = pz.z + 3}
-			end
-		end
+		dofile(nether.path .. "/mapgen_nobiomes.lua")
 	end
 end
+dofile(nether.path .. "/portal_examples.lua")
 
 
-local function make_portal(pos)
-	local p1, p2 = is_portal(pos)
-	if not p1 or not p2 then
-		return false
-	end
-
-	for d = 1, 2 do
-	for y = p1.y + 1, p2.y - 1 do
-		local p
-		if p1.z == p2.z then
-			p = {x = p1.x + d, y = y, z = p1.z}
-		else
-			p = {x = p1.x, y = y, z = p1.z + d}
-		end
-		if minetest.get_node(p).name ~= "air" then
-			return false
-		end
-	end
-	end
-
-	local param2
-	if p1.z == p2.z then
-		param2 = 0
-	else
-		param2 = 1
-	end
-
-	local target = {x = p1.x, y = p1.y, z = p1.z}
-	target.x = target.x + 1
-	if target.y < NETHER_DEPTH then
-		target.y = find_surface_target_y(target.x, target.z, -16)
-	else
-		local start_y = NETHER_DEPTH - math.random(500, 1500) -- Search start
-		target.y = find_nether_target_y(target.x, target.z, start_y)
-	end
-
-	for d = 0, 3 do
-	for y = p1.y, p2.y do
-		local p
-		if param2 == 0 then
-			p = {x = p1.x + d, y = y, z = p1.z}
-		else
-			p = {x = p1.x, y = y, z = p1.z + d}
-		end
-		if minetest.get_node(p).name == "air" then
-			minetest.set_node(p, {name = "nether:portal", param2 = param2})
-		end
-		local meta = minetest.get_meta(p)
-		meta:set_string("p1", minetest.pos_to_string(p1))
-		meta:set_string("p2", minetest.pos_to_string(p2))
-		meta:set_string("target", minetest.pos_to_string(target))
-	end
-	end
-
-	return true
-end
-
-
--- ABMs
-
-minetest.register_abm({
-	nodenames = {"nether:portal"},
-	interval = 1,
-	chance = 2,
-	action = function(pos, node)
-		minetest.add_particlespawner({
-			32, --amount
-			4, --time
-			{x = pos.x - 0.25, y = pos.y - 0.25, z = pos.z - 0.25}, --minpos
-			{x = pos.x + 0.25, y = pos.y + 0.25, z = pos.z + 0.25}, --maxpos
-			{x = -0.8, y = -0.8, z = -0.8}, --minvel
-			{x = 0.8, y = 0.8, z = 0.8}, --maxvel
-			{x = 0, y = 0, z = 0}, --minacc
-			{x = 0, y = 0, z = 0}, --maxacc
-			0.5, --minexptime
-			1, --maxexptime
-			1, --minsize
-			2, --maxsize
-			false, --collisiondetection
-			"nether_particle.png" --texture
-		})
-		for _, obj in ipairs(minetest.get_objects_inside_radius(pos, 1)) do
-			if obj:is_player() then
-				local meta = minetest.get_meta(pos)
-				local target = minetest.string_to_pos(meta:get_string("target"))
-				if target then
-					-- force emerge of target area
-					minetest.get_voxel_manip():read_from_map(target, target)
-					if not minetest.get_node_or_nil(target) then
-						minetest.emerge_area(
-							vector.subtract(target, 4), vector.add(target, 4))
-					end
-					-- teleport the player
-					minetest.after(3, function(o, p, t)
-						local objpos = o:getpos()
-						objpos.y = objpos.y + 0.1 -- Fix some glitches at -8000
-						if minetest.get_node(objpos).name ~= "nether:portal" then
-							return
-						end
-
-						o:setpos(t)
-
-						local function check_and_build_portal(pp, tt)
-							local n = minetest.get_node_or_nil(tt)
-							if n and n.name ~= "nether:portal" then
-								build_portal(tt, pp)
-								minetest.after(2, check_and_build_portal, pp, tt)
-								minetest.after(4, check_and_build_portal, pp, tt)
-							elseif not n then
-								minetest.after(1, check_and_build_portal, pp, tt)
-							end
-						end
-
-						minetest.after(1, check_and_build_portal, p, t)
-
-					end, obj, pos, target)
-				end
-			end
-		end
-	end,
-})
-
-
--- Nodes
-
-minetest.register_node("nether:portal", {
-	description = "Nether Portal",
-	tiles = {
-		"nether_transparent.png",
-		"nether_transparent.png",
-		"nether_transparent.png",
-		"nether_transparent.png",
-		{
-			name = "nether_portal.png",
-			animation = {
-				type = "vertical_frames",
-				aspect_w = 16,
-				aspect_h = 16,
-				length = 0.5,
-			},
-		},
-		{
-			name = "nether_portal.png",
-			animation = {
-				type = "vertical_frames",
-				aspect_w = 16,
-				aspect_h = 16,
-				length = 0.5,
-			},
-		},
-	},
-	drawtype = "nodebox",
-	paramtype = "light",
-	paramtype2 = "facedir",
-	sunlight_propagates = true,
-	use_texture_alpha = true,
-	walkable = false,
-	diggable = false,
-	pointable = false,
-	buildable_to = false,
-	is_ground_content = false,
-	drop = "",
-	light_source = 5,
-	post_effect_color = {a = 180, r = 128, g = 0, b = 128},
-	alpha = 192,
-	node_box = {
-		type = "fixed",
-		fixed = {
-			{-0.5, -0.5, -0.1,  0.5, 0.5, 0.1},
-		},
-	},
-	groups = {not_in_creative_inventory = 1}
-})
-
-minetest.register_node(":default:obsidian", {
-	description = "Obsidian",
-	tiles = {"default_obsidian.png"},
-	is_ground_content = false,
-	sounds = default.node_sound_stone_defaults(),
-	groups = {cracky = 1, level = 2},
-
-	on_destruct = function(pos)
-		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 not p1 or not p2 then
-			return
-		end
-
-		for x = p1.x, p2.x do
-		for y = p1.y, p2.y do
-		for z = p1.z, p2.z do
-			local nn = minetest.get_node({x = x, y = y, z = z}).name
-			if nn == "default:obsidian" or nn == "nether:portal" then
-				if nn == "nether:portal" then
-					minetest.remove_node({x = x, y = y, z = z})
-				end
-				local m = minetest.get_meta({x = x, y = y, z = z})
-				m:set_string("p1", "")
-				m:set_string("p2", "")
-				m:set_string("target", "")
-			end
-		end
-		end
-		end
-
-		meta = minetest.get_meta(target)
-		if not meta then
-			return
-		end
-		p1 = minetest.string_to_pos(meta:get_string("p1"))
-		p2 = minetest.string_to_pos(meta:get_string("p2"))
-		if not p1 or not p2 then
-			return
-		end
-
-		for x = p1.x, p2.x do
-		for y = p1.y, p2.y do
-		for z = p1.z, p2.z do
-			local nn = minetest.get_node({x = x, y = y, z = z}).name
-			if nn == "default:obsidian" or nn == "nether:portal" then
-				if nn == "nether:portal" then
-					minetest.remove_node({x = x, y = y, z = z})
-				end
-				local m = minetest.get_meta({x = x, y = y, z = z})
-				m:set_string("p1", "")
-				m:set_string("p2", "")
-				m:set_string("target", "")
-			end
-		end
-		end
-		end
-	end,
-})
-
-minetest.register_node("nether:rack", {
-	description = "Netherrack",
-	tiles = {"nether_rack.png"},
-	is_ground_content = true,
-	groups = {cracky = 3, level = 2},
-	sounds = default.node_sound_stone_defaults(),
-})
-
-minetest.register_node("nether:sand", {
-	description = "Nethersand",
-	tiles = {"nether_sand.png"},
-	is_ground_content = true,
-	groups = {crumbly = 3, level = 2, falling_node = 1},
-	sounds = default.node_sound_gravel_defaults({
-		footstep = {name = "default_gravel_footstep", gain = 0.45},
-	}),
-})
-
-minetest.register_node("nether:glowstone", {
-	description = "Glowstone",
-	tiles = {"nether_glowstone.png"},
-	is_ground_content = true,
-	light_source = 14,
-	paramtype = "light",
-	groups = {cracky = 3, oddly_breakable_by_hand = 3},
-	sounds = default.node_sound_glass_defaults(),
-})
-
-minetest.register_node("nether:brick", {
-	description = "Nether Brick",
-	tiles = {"nether_brick.png"},
-	is_ground_content = false,
-	groups = {cracky = 2, level = 2},
-	sounds = default.node_sound_stone_defaults(),
-})
-
-local fence_texture =
-	"default_fence_overlay.png^nether_brick.png^default_fence_overlay.png^[makealpha:255,126,126"
-
-minetest.register_node("nether:fence_nether_brick", {
-	description = "Nether Brick Fence",
-	drawtype = "fencelike",
-	tiles = {"nether_brick.png"},
-	inventory_image = fence_texture,
-	wield_image = fence_texture,
-	paramtype = "light",
-	sunlight_propagates = true,
-	is_ground_content = false,
-	selection_box = {
-		type = "fixed",
-		fixed = {-1/7, -1/2, -1/7, 1/7, 1/2, 1/7},
-	},
-	groups = {cracky = 2, level = 2},
-	sounds = default.node_sound_stone_defaults(),
-})
-
-
--- Register stair and slab
-
-stairs.register_stair_and_slab(
-	"nether_brick",
-	"nether:brick",
-	{cracky = 2, level = 2},
-	{"nether_brick.png"},
-	"nether stair",
-	"nether slab",
-	default.node_sound_stone_defaults()
+-- Portals are ignited by right-clicking with a mese crystal fragment
+nether.register_portal_ignition_item(
+	"default:mese_crystal_fragment",
+	{name = "nether_portal_ignition_failure", gain = 0.3}
 )
 
--- StairsPlus
 
-if minetest.get_modpath("moreblocks") then
-	stairsplus:register_all(
-		"nether", "brick", "nether:brick", {
-			description = "Nether Brick",
-			groups = {cracky = 2, level = 2},
-			tiles = {"nether_brick.png"},
-			sounds = default.node_sound_stone_defaults(),
+if nether.NETHER_REALM_ENABLED then
+	-- Use the Portal API to add a portal type which goes to the Nether
+	-- See portal_api.txt for documentation
+	nether.register_portal("nether_portal", {
+		shape               = nether.PortalShape_Traditional,
+		frame_node_name     = "default:obsidian",
+		wormhole_node_color = 0, -- 0 is magenta
+		title = S("Nether Portal"),
+		book_of_portals_pagetext = S([[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.
+
+This 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.
+
+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_CEILING
+		end,
+
+		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_CEILING - 1000 -- 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 =
+				nether.find_nearest_working_portal("nether_portal", destination_pos, 8, 0)
+
+			if existing_portal_location ~= nil then
+				return existing_portal_location, existing_portal_orientation
+			else
+				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, 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.
+			-- Defining a custom function also means we can look for existing nearby portals.
+
+			-- Multiply x and z by a factor of 8 to implement Nether fast-travel
+			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
+
+			-- 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 =
+				nether.find_nearest_working_portal("nether_portal", destination_pos, 8 * nether.FASTTRAVEL_FACTOR, 0)
+
+			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", player_name)
+				return destination_pos
+			end
+		end,
+
+		on_ignite = function(portalDef, anchorPos, orientation)
+
+			-- make some sparks fly
+			local p1, p2 = portalDef.shape:get_p1_and_p2_from_anchorPos(anchorPos, orientation)
+			local pos = vector.divide(vector.add(p1, p2), 2)
+
+			local textureName = portalDef.particle_texture
+			if type(textureName) == "table" then textureName = textureName.name end
+
+			minetest.add_particlespawner({
+				amount = 110,
+				time   = 0.1,
+				minpos = {x = pos.x - 0.5, y = pos.y - 1.2, z = pos.z - 0.5},
+				maxpos = {x = pos.x + 0.5, y = pos.y + 1.2, z = pos.z + 0.5},
+				minvel = {x = -5, y = -1, z = -5},
+				maxvel = {x =  5, y =  1, z =  5},
+				minacc = {x =  0, y =  0, z =  0},
+				maxacc = {x =  0, y =  0, z =  0},
+				minexptime = 0.1,
+				maxexptime = 0.5,
+				minsize = 0.2 * portalDef.particle_texture_scale,
+				maxsize = 0.8 * portalDef.particle_texture_scale,
+				collisiondetection = false,
+				texture = textureName .. "^[colorize:#F4F:alpha",
+				animation = portalDef.particle_texture_animation,
+				glow = 8
+			})
+
+		end
+
 	})
 end
 
-stairs.register_stair_and_slab("brick", "nether:brick",
-	{cracky=3, oddly_breakable_by_hand=1},
-	{"nether_brick.png"},
-	"nether stair",
-	"nether slab",
-	default.node_sound_stone_defaults())
 
-
--- Craftitems
-
-minetest.override_item("default:mese_crystal_fragment", {
-	on_place = function(stack, _, pt)
-		if pt.under and minetest.get_node(pt.under).name == "default:obsidian" then
-			local done = make_portal(pt.under)
-			if done and not minetest.settings:get_bool("creative_mode") then
-				stack:take_item()
-			end
-		end
-
-		return stack
-	end,
-})
-
--- Crafting
-
-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"},
-	},
-})
-
-
--- Mapgen
-
--- Initialize noise object, localise noise and data buffers
-
-local nobj_cave = nil
-local nbuf_cave = nil
-local dbuf = nil
-
-
--- 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_DEPTH 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 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:get3dMap_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
-			if y > yblmax then
-				tcave = TCAVE + ((y - yblmax) / BLEND) ^ 2
-			else
-				tcave = TCAVE
-			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
+-- 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
-
-	vm:set_data(data)
-	vm:set_lighting({day = 0, night = 0})
-	vm:calc_lighting()
-	vm:update_liquids()
-	vm:write_to_map()
-end)
+)

locale/nether.fr.tr

@@ -0,0 +1,99 @@
+# textdomain: nether
+
+# Translation FR by Louis Royer
+
+
+### 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
+
+### nodes.lua ###
+
+=
+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 Netherrack=
+Fumarolic Chimney=
+Fumarolic Chimney Corner=
+Fumarolic Chimney Slab=
+Glowstone=Pierre lumineuse
+Hewn Basalt=
+Inner Nether Stair=Escalier intérieur du Nether
+Lava Crust=
+
+Lava crust is strong enough to walk on, but still hot enough to inflict burns.=
+
+Nether Basalt=
+Nether Brick=Brique du Nether
+Nether Brick Fence=Barrière en briques du Nether
+Nether Slab=Dalle du Nether
+Nether Stair=Escalier du Nether
+Netherrack=Roche du Nether
+Netherrack from deep in the mantle=
+Netherrack stair=
+Nethersand=Sable du Nether
+Outer Nether Stair=Escalier extérieur du Nether
+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.=@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=
+
+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=
+Nether Ingot=
+Nether Lump=
+Nether Pickaxe=
+Nether Shovel=
+Nether Sword=

locale/template.txt

@@ -0,0 +1,98 @@
+# 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=
+
+### nodes.lua ###
+
+=
+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 Netherrack=
+Fumarolic Chimney=
+Fumarolic Chimney Corner=
+Fumarolic Chimney Slab=
+Glowstone=
+Hewn Basalt=
+Inner Nether Stair=
+Lava Crust=
+
+Lava crust is strong enough to walk on, but still hot enough to inflict burns.=
+
+Nether Basalt=
+Nether Brick=
+Nether Brick Fence=
+Nether Slab=
+Nether Stair=
+Netherrack=
+Netherrack from deep in the mantle=
+Netherrack stair=
+Nethersand=
+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=
+Nether Shovel=
+Nether Sword=

mapgen.lua

@@ -0,0 +1,684 @@
+--[[
+
+  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
+  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
+
+-- 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
+nether.mapgen = {}
+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 helper functions for generating the mantle / center region
+dofile(nether.path .. "/mapgen_mantle.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
+
+local function override_underground_biomes()
+	-- 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
+		local biome_y_max, biome_y_min = tonumber(new_biome_def.y_max), tonumber(new_biome_def.y_min)
+
+		if biome_y_max > NETHER_FLOOR and biome_y_min < NETHER_CEILING then
+			-- This biome occupies some or all of the depth of the Nether, shift/crop it.
+			local spaceOccupiedAbove = biome_y_max - NETHER_CEILING
+			local spaceOccupiedBelow = NETHER_FLOOR - 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_biome_def.y_min = NETHER_CEILING + 1
+				new_biome_def.y_max = math_max(biome_y_max, NETHER_CEILING + 2)
+			else
+				-- shift the biome to below the Nether
+				new_biome_def.y_max = NETHER_FLOOR - 1
+				new_biome_def.y_min = math_min(biome_y_min, NETHER_CEILING - 2)
+			end
+		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
+override_underground_biomes()
+
+-- 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.
+minetest.register_node("nether:native_mapgen", {})
+
+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
+
+mapgen.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 = ""
+}
+
+-- Buffers and objects we shouldn't recreate every on_generate
+
+local nobj_cave = nil
+local nbuf_cave = {}
+local dbuf = {}
+
+
+-- 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_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_lava_source      = minetest.get_content_id("default:lava_source")
+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")
+
+
+-- Dungeon excavation functions
+
+function is_dungeon_brick(node_id)
+	return node_id == c_dungeonbrick or node_id == c_dungeonbrick_alt
+end
+
+function build_dungeon_room_list(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)
+function excavate_dungeons(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 then data[vi] = c_air end
+					vi = vi + 1
+				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.
+function decorate_dungeons(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)
+
+			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 room_max.x - room_min.x >= 4 and room_max.z - room_min.z >= 4
+			   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
+
+				-- Until whisper glass is added, every window will be made of netherbrick fence (rather
+				-- than material depending on room_seed)
+				local window_node = c_netherfence
+
+				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 _, offset in ipairs(locations) do
+					if is_dungeon_brick(data[vi_min + offset]) then data[vi_min + offset] = window_node end
+					if is_dungeon_brick(data[vi_max + offset]) then data[vi_max + offset] = window_node end
+				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 _, offset in ipairs(locations) do
+					if is_dungeon_brick(data[vi_min + offset]) then data[vi_min + offset] = window_node end
+					if is_dungeon_brick(data[vi_max + offset]) then data[vi_max + offset] = window_node end
+				end
+			end
+
+			-- Weeds on the floor once Nether weeds are added
+		end
+	end
+end
+
+
+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)
+
+	-- 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
+
+
+
+-- On-generated function
+
+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 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 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 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(mapgen.np_cave, chulens)
+	local nvals_cave = nobj_cave:get_3d_map_flat(minp, nbuf_cave)
+
+	local dungeonRooms = build_dungeon_room_list(data, area)
+	local abs_cave_noise, abs_cave_noise_adjusted
+
+	local contains_nether = false
+	local contains_shell  = false
+	local contains_mantle = false
+	local contains_ocean = false
+
+
+	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 provided by 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
+		local cavern_noise_adj =
+			CENTER_REGION_LIMIT * (cavern_limit_distance * cavern_limit_distance * cavern_limit_distance) -
+			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
+
+		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.
+					data[vi] = c_air
+					contains_nether = true
+
+				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] = c_netherrack -- For now I've just left this region as solid netherrack instead of air.
+
+					-- Only set contains_nether to true here if you want tunnels created between the secondary region
+					-- and the central region.
+					--contains_nether = true
+					--data[vi] = c_air
+				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...
+								data[vi] = c_netherrack -- excavate_dungeons() will mostly reverse this inside dungeons
+								contains_shell = true
+							end
+						end
+
+					elseif above_lavasea then
+						data[vi] = c_air
+						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
+				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 provided by 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 provided by 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.
+	excavate_dungeons(data, area, dungeonRooms)
+	decorate_dungeons(data, area, dungeonRooms)
+
+	vm:set_data(data)
+
+	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
+
+
+-- 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(mapgen.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:get3d({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
+
+-- 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})
+
+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_mantle.lua

@@ -0,0 +1,476 @@
+--[[
+
+  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 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 = {}
+local cavePerlin = nil
+
+-- 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
+
+	cavePerlin = cavePerlin or minetest.get_perlin(mapgen.np_cave)
+	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:get3d({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 sealevel, cavern_limit_distance = mapgen.find_nearest_lava_sealevel(mantle_y)
+		local _, centerRegionLimit_adj = mapgen.get_mapgenblend_adjustments(mantle_y)
+		local cavern_noise_adj =
+			mapgen.CENTER_REGION_LIMIT * (cavern_limit_distance * cavern_limit_distance * cavern_limit_distance) -
+			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
+
+		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
+
+
+minetest.register_chatcommand("nether_whereami",
+    {
+		description = "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, "Unknown player position" end
+
+			local pos = vector.round(player:get_pos())
+			if pos.y > nether.DEPTH_CEILING or pos.y < nether.DEPTH_FLOOR then
+				return true, "The Overworld"
+			end
+
+			cavePerlin = cavePerlin or minetest.get_perlin(mapgen.np_cave)
+			local densityNoise = cavePerlin:get_3d(pos)
+			local sea_level, 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
+			local cavern_noise_adj =
+				mapgen.CENTER_REGION_LIMIT * (cavern_limit_distance * cavern_limit_distance * cavern_limit_distance) -
+				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 so subtract centerRegionLimit_adj instead of adding
+
+			local desc
+
+			if densityNoise > tcave then
+				desc = "Positive nether"
+			elseif -densityNoise > tcave then
+				desc = "Negative nether"
+			elseif math_abs(densityNoise) < tmantle then
+				desc =  "Mantle"
+
+				if math_abs(densityNoise) + cavern_noise_adj < mapgen.CENTER_CAVERN_LIMIT then
+					desc =  desc .. " inside cavern"
+				else
+					desc =  desc .. " but outside cavern"
+				end
+
+			elseif densityNoise > 0 then
+				desc =  "Shell between positive nether and center region"
+			else
+				desc = "Shell between negative nether and center region"
+			end
+
+			local sea_pos = pos.y - sea_level
+			if sea_pos > 0 then
+				desc = desc .. ", " .. sea_pos .. "m above lava-sea level"
+			else
+				desc = desc .. ", " .. sea_pos .. "m below lava-sea level"
+			end
+
+			if tcave_adj > 0 then
+				desc = desc .. ", approaching y boundary of Nether"
+			end
+
+			return true, "[Perlin " .. (math_floor(densityNoise * 1000) / 1000) .. "] " .. desc
+		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:get3d({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 = moreblocks, mesecons, loot, dungeon_loot, doc_basics, fire

nodes.lua

@@ -0,0 +1,773 @@
+--[[
+
+  Nether mod for minetest
+
+  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.
+
+]]--
+
+local S = nether.get_translator
+
+-- Portal/wormhole nodes
+
+nether.register_wormhole_node("nether:portal", {
+	description = S("Nether Portal"),
+	post_effect_color = {
+		-- post_effect_color can't be changed dynamically in Minetest like the portal colour is.
+		-- If you need a different post_effect_color then use register_wormhole_node to create
+		-- another wormhole node and set it as the wormhole_node_name in your portaldef.
+		-- Hopefully this colour is close enough to magenta to work with the traditional magenta
+		-- portals, close enough to red to work for a red portal, and also close enough to red to
+		-- work with blue & cyan portals - since blue portals are sometimes portrayed as being red
+		-- from the opposite side / from the inside.
+		a = 160, r = 128, g = 0, b = 80
+	}
+})
+
+local portal_animation2 = {
+	name = "nether_portal_alt.png",
+	animation = {
+		type = "vertical_frames",
+		aspect_w = 16,
+		aspect_h = 16,
+		length = 0.5,
+	},
+}
+
+nether.register_wormhole_node("nether:portal_alt", {
+	description = S("Portal"),
+	tiles = {
+		"nether_transparent.png",
+		"nether_transparent.png",
+		"nether_transparent.png",
+		"nether_transparent.png",
+		portal_animation2,
+		portal_animation2
+	},
+	post_effect_color = {
+		-- hopefully blue enough to work with blue portals, and green enough to
+		-- work with cyan portals.
+		a = 120, r = 0, g = 128, b = 188
+	}
+})
+
+
+-- Nether nodes
+
+minetest.register_node("nether:rack", {
+	description = S("Netherrack"),
+	tiles = {"nether_rack.png"},
+	is_ground_content = true,
+	groups = {cracky = 3, level = 2},
+	sounds = default.node_sound_stone_defaults(),
+})
+
+-- Deep Netherrack, found in the mantle / central magma layers
+minetest.register_node("nether:rack_deep", {
+	description = S("Deep Netherrack"),
+	_doc_items_longdesc = S("Netherrack from deep in the mantle"),
+	tiles = {"nether_rack_deep.png"},
+	is_ground_content = true,
+	groups = {cracky = 3, level = 2},
+	sounds = default.node_sound_stone_defaults(),
+})
+
+minetest.register_node("nether:sand", {
+	description = S("Nethersand"),
+	tiles = {"nether_sand.png"},
+	is_ground_content = true,
+	groups = {crumbly = 3, level = 2, falling_node = 1},
+	sounds = default.node_sound_gravel_defaults({
+		footstep = {name = "default_gravel_footstep", gain = 0.45},
+	}),
+})
+
+minetest.register_node("nether:glowstone", {
+	description = S("Glowstone"),
+	tiles = {"nether_glowstone.png"},
+	is_ground_content = true,
+	light_source = 14,
+	paramtype = "light",
+	groups = {cracky = 3, oddly_breakable_by_hand = 3},
+	sounds = default.node_sound_glass_defaults(),
+})
+
+-- Deep glowstone, found in the mantle / central magma layers
+minetest.register_node("nether:glowstone_deep", {
+	description = S("Deep Glowstone"),
+	tiles = {"nether_glowstone_deep.png"},
+	is_ground_content = true,
+	light_source = 14,
+	paramtype = "light",
+	groups = {cracky = 3, oddly_breakable_by_hand = 3},
+	sounds = default.node_sound_glass_defaults(),
+})
+
+minetest.register_node("nether:brick", {
+	description = S("Nether Brick"),
+	tiles = {"nether_brick.png"},
+	is_ground_content = false,
+	groups = {cracky = 2, level = 2},
+	sounds = default.node_sound_stone_defaults(),
+})
+
+minetest.register_node("nether:brick_compressed", {
+	description = S("Compressed Netherbrick"),
+	tiles = {"nether_brick_compressed.png"},
+	groups = {cracky = 3, level = 2},
+	is_ground_content = false,
+	sounds = default.node_sound_stone_defaults(),
+})
+
+-- A decorative node which can only be obtained from dungeons or structures
+minetest.register_node("nether:brick_cracked", {
+	description = S("Cracked Nether Brick"),
+	tiles = {"nether_brick_cracked.png"},
+	is_ground_content = false,
+	groups = {cracky = 2, level = 2},
+	sounds = default.node_sound_stone_defaults(),
+})
+
+local fence_texture =
+	"default_fence_overlay.png^nether_brick.png^default_fence_overlay.png^[makealpha:255,126,126"
+
+minetest.register_node("nether:fence_nether_brick", {
+	description = S("Nether Brick Fence"),
+	drawtype = "fencelike",
+	tiles = {"nether_brick.png"},
+	inventory_image = fence_texture,
+	wield_image = fence_texture,
+	paramtype = "light",
+	sunlight_propagates = true,
+	is_ground_content = false,
+	selection_box = {
+		type = "fixed",
+		fixed = {-1/7, -1/2, -1/7, 1/7, 1/2, 1/7},
+	},
+	groups = {cracky = 2, level = 2},
+	sounds = default.node_sound_stone_defaults(),
+})
+
+
+-- Register stair and slab
+
+stairs.register_stair_and_slab(
+	"nether_brick",
+	"nether:brick",
+	{cracky = 2, level = 2},
+	{"nether_brick.png"},
+	S("Nether Stair"),
+	S("Nether Slab"),
+	default.node_sound_stone_defaults(),
+	nil,
+	S("Inner Nether Stair"),
+	S("Outer Nether Stair")
+)
+
+stairs.register_stair(
+	"netherrack",
+	"nether:rack",
+	{cracky = 2, level = 2},
+	{"nether_rack.png"},
+	S("Netherrack stair"),
+	default.node_sound_stone_defaults()
+)
+
+-- StairsPlus
+
+if minetest.get_modpath("moreblocks") then
+	stairsplus:register_all(
+		"nether", "brick", "nether:brick", {
+			description = S("Nether Brick"),
+			groups = {cracky = 2, level = 2},
+			tiles = {"nether_brick.png"},
+			sounds = default.node_sound_stone_defaults(),
+	})
+end
+
+
+-- Mantle nodes
+
+-- Nether basalt is intended as a valuable material and possible portalstone - an alternative to
+-- obsidian that's available for other mods to use.
+-- It cannot be found in the regions of the nether where Nether portals link to, so requires a journey to obtain.
+minetest.register_node("nether:basalt", {
+	description = S("Nether Basalt"),
+	_doc_items_longdesc = S("Columns of dark basalt found only in magma oceans deep within the Nether."),
+	tiles = {
+		"nether_basalt.png",
+		"nether_basalt.png",
+		"nether_basalt_side.png",
+		"nether_basalt_side.png",
+		"nether_basalt_side.png",
+		"nether_basalt_side.png"
+	},
+	is_ground_content = true,
+	groups = {cracky = 1, level = 3}, -- set proper digging times and uses, and maybe explosion immune if api handles that
+	on_blast = function() --[[blast proof]] end,
+	sounds = default.node_sound_stone_defaults(),
+})
+
+-- Potentially a portalstone, but will also be a stepping stone between basalt
+-- and chiseled basalt.
+-- It can only be introduced by the biomes-based mapgen, since it requires the
+-- MT 5.0 world-align texture features.
+minetest.register_node("nether:basalt_hewn", {
+	description = S("Hewn Basalt"),
+	_doc_items_longdesc = S("A rough cut solid block of Nether Basalt."),
+	tiles = {{
+		name        = "nether_basalt_hewn.png",
+		align_style = "world",
+		scale       = 2
+	}},
+	inventory_image = minetest.inventorycube(
+		"nether_basalt_hewn.png^[sheet:2x2:0,0",
+		"nether_basalt_hewn.png^[sheet:2x2:0,1",
+		"nether_basalt_hewn.png^[sheet:2x2:1,1"
+	),
+	is_ground_content = false,
+	groups = {cracky = 1, level = 2},
+	on_blast = function() --[[blast proof]] end,
+	sounds = default.node_sound_stone_defaults(),
+})
+
+-- Chiselled basalt is intended as a portalstone - an alternative to obsidian that's
+-- available for other mods to use. It is crafted from Hewn Basalt.
+-- It should only be introduced by the biomes-based mapgen, since in future it may
+-- require the MT 5.0 world-align texture features.
+minetest.register_node("nether:basalt_chiselled", {
+	description = S("Chiselled Basalt"),
+	_doc_items_longdesc = S("A finely finished block of solid Nether Basalt."),
+	tiles = {
+		"nether_basalt_chiselled_top.png",
+		"nether_basalt_chiselled_top.png" .. "^[transformFY",
+		"nether_basalt_chiselled_side.png",
+		"nether_basalt_chiselled_side.png",
+		"nether_basalt_chiselled_side.png",
+		"nether_basalt_chiselled_side.png"
+	},
+	inventory_image = minetest.inventorycube(
+		"nether_basalt_chiselled_top.png",
+		"nether_basalt_chiselled_side.png",
+		"nether_basalt_chiselled_side.png"
+	),
+	paramtype2 = "facedir",
+	is_ground_content = false,
+	groups = {cracky = 1, level = 2},
+	on_blast = function() --[[blast proof]] end,
+	sounds = default.node_sound_stone_defaults(),
+})
+
+
+-- Lava-sea source
+-- This is a lava source using a different animated texture so that each node
+-- is out of phase in its animation from its neighbor. This prevents the magma
+-- ocean from visually clumping together into a patchwork of 16x16 squares.
+-- It can only be used by the biomes-based mapgen, since it requires the MT 5.0
+-- world-align texture features.
+local lavasea_source = {}
+local lava_source = minetest.registered_nodes["default:lava_source"]
+for key, value in pairs(lava_source) do lavasea_source[key] = value end
+lavasea_source.name = nil
+lavasea_source.tiles = {
+	{
+		name             = "nether_lava_source_animated.png",
+		backface_culling = false,
+		align_style      = "world",
+		scale            = 2,
+		animation = {
+			type     = "vertical_frames",
+			aspect_w = 32,
+			aspect_h = 32,
+			length   = 3.0,
+		},
+	},
+	{
+		name             = "nether_lava_source_animated.png",
+		backface_culling = true,
+		align_style      = "world",
+		scale            = 2,
+		animation = {
+			type     = "vertical_frames",
+			aspect_w = 32,
+			aspect_h = 32,
+			length   = 3.0,
+		},
+	},
+}
+lavasea_source.liquid_alternative_source = "nether:lava_source"
+lavasea_source.inventory_image = minetest.inventorycube(
+	"nether_lava_source_animated.png^[sheet:2x16:0,0",
+	"nether_lava_source_animated.png^[sheet:2x16:0,1",
+	"nether_lava_source_animated.png^[sheet:2x16:1,1"
+)
+minetest.register_node("nether:lava_source", lavasea_source)
+
+
+-- a place to store the original ABM function so nether.cool_lava() can call it
+local original_cool_lava_action
+
+nether.cool_lava = function(pos, node)
+
+	local pos_above = {x = pos.x, y = pos.y + 1, z = pos.z}
+	local node_above = minetest.get_node(pos_above)
+
+	-- Evaporate water sitting above lava, if it's in the Nether.
+	-- (we don't want Nether mod to affect overworld lava mechanics)
+	if minetest.get_node_group(node_above.name, "water") > 0 and
+		pos.y < nether.DEPTH_CEILING and pos.y > nether.DEPTH_FLOOR then
+		-- cools_lava might be a better group to check for, but perhaps there's
+		-- something in that group that isn't a liquid and shouldn't be evaporated?
+		minetest.swap_node(pos_above, {name="air"})
+	end
+
+	-- add steam to cooling lava
+	minetest.add_particlespawner({
+		amount = 20,
+		time = 0.15,
+		minpos = {x=pos.x - 0.4, y=pos.y - 0,   z=pos.z - 0.4},
+		maxpos = {x=pos.x + 0.4, y=pos.y + 0.5, z=pos.z + 0.4},
+		minvel = {x = -0.5, y = 0.5, z = -0.5},
+		maxvel = {x =  0.5, y = 1.5, z =  0.5},
+		minacc = {x = 0, y = 0.1, z = 0},
+		maxacc = {x = 0, y = 0.2, z = 0},
+		minexptime = 0.5,
+		maxexptime = 1.3,
+		minsize = 1.5,
+		maxsize = 3.5,
+		texture = "nether_particle_anim4.png",
+		animation = {
+			type = "vertical_frames",
+			aspect_w = 7,
+			aspect_h = 7,
+			length = 1.4,
+		}
+	})
+
+	if node.name == "nether:lava_source" or node.name == "nether:lava_crust" then
+		-- use swap_node to avoid triggering the lava_crust's after_destruct
+		minetest.swap_node(pos, {name = "nether:basalt"})
+
+		minetest.sound_play("default_cool_lava",
+			{pos = pos, max_hear_distance = 16, gain = 0.25}, true)
+	else
+		-- chain the original ABM action to handle conventional lava
+		original_cool_lava_action(pos, node)
+	end
+end
+
+
+minetest.register_on_mods_loaded(function()
+
+	-- register a bucket of Lava-sea source - but make it just the same bucket as default lava.
+	-- (by doing this in register_on_mods_loaded we don't need to declare a soft dependency)
+	if minetest.get_modpath("bucket") and minetest.global_exists("bucket") then
+		local lava_bucket = bucket.liquids["default:lava_source"]
+		if lava_bucket ~= nil then
+			local lavasea_bucket = {}
+			for key, value in pairs(lava_bucket) do lavasea_bucket[key] = value end
+			lavasea_bucket.source = "nether:lava_source"
+			bucket.liquids[lavasea_bucket.source] = lavasea_bucket
+		end
+	end
+
+	-- include "nether:lava_source" in any "default:lava_source" ABMs
+	local function include_nether_lava(set_of_nodes)
+		if (type(set_of_nodes) == "table") then
+			for _, nodename in pairs(set_of_nodes) do
+				if nodename == "default:lava_source" then
+					-- I'm amazed this works, but it does
+					table.insert(set_of_nodes, "nether:lava_source")
+					break;
+				end
+			end
+		end
+	end
+
+	for _, abm in pairs(minetest.registered_abms) do
+		include_nether_lava(abm.nodenames)
+		include_nether_lava(abm.neighbors)
+		if abm.label == "Lava cooling" and abm.action ~= nil then
+			-- lets have lava_crust cool as well
+			original_cool_lava_action = abm.action
+			abm.action = nether.cool_lava
+			table.insert(abm.nodenames, "nether:lava_crust")
+		end
+	end
+	for _, lbm in pairs(minetest.registered_lbms) do
+		include_nether_lava(lbm.nodenames)
+	end
+	--minetest.log("minetest.registered_abms" .. dump(minetest.registered_abms))
+	--minetest.log("minetest.registered_lbms" .. dump(minetest.registered_lbms))
+end)
+
+-- creates a lava splash, and leaves lava_source in place of the lava_crust
+local function smash_lava_crust(pos, playsound)
+
+	local lava_particlespawn_def = {
+		amount = 6,
+		time = 0.1,
+		minpos = {x=pos.x - 0.5, y=pos.y + 0.3, z=pos.z - 0.5},
+		maxpos = {x=pos.x + 0.5, y=pos.y + 0.5, z=pos.z + 0.5},
+		minvel = {x = -1.5, y = 1.5, z = -1.5},
+		maxvel = {x =  1.5, y = 5,   z =  1.5},
+		minacc = {x = 0, y = -10, z = 0},
+		maxacc = {x = 0, y = -10, z = 0},
+		minexptime = 1,
+		maxexptime = 1,
+		minsize = .2,
+		maxsize = .8,
+		texture = "^[colorize:#A00:255",
+		glow = 8
+	}
+	minetest.add_particlespawner(lava_particlespawn_def)
+	lava_particlespawn_def.texture = "^[colorize:#FB0:255"
+	lava_particlespawn_def.maxvel.y = 3
+	lava_particlespawn_def.glow = 12
+	minetest.add_particlespawner(lava_particlespawn_def)
+
+	minetest.set_node(pos, {name = "default:lava_source"})
+
+	if math.random(1, 3) == 1 and minetest.registered_nodes["fire:basic_flame"] ~= nil then
+		-- occasionally brief flames will be seen when breaking lava crust
+		local posAbove = {x = pos.x, y = pos.y + 1, z = pos.z}
+		if minetest.get_node(posAbove).name == "air" then
+			minetest.set_node(posAbove, {name = "fire:basic_flame"})
+			minetest.get_node_timer(posAbove):set(math.random(7, 15) / 10, 0)
+			--[[ commented out because the flame sound plays for too long
+			if minetest.global_exists("fire") and fire.update_player_sound ~= nil then
+				-- The fire mod only updates its sound every 3 seconds, these flames will be
+				-- out by then, so start the sound immediately
+				local players = minetest.get_connected_players()
+				for n = 1, #players do fire.update_player_sound(players[n]) end
+			end]]
+		end
+	end
+
+	if playsound 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
+			{pos = pos, pitch = 0.3, max_hear_distance = 8, gain = 0.4}
+		)
+	end
+end
+
+
+-- lava_crust nodes can only be used in the biomes-based mapgen, since they require
+-- the MT 5.0 world-align texture features.
+minetest.register_node("nether:lava_crust", {
+	description = S("Lava Crust"),
+	_doc_items_longdesc = S("A thin crust of cooled lava with liquid lava beneath"),
+	_doc_items_usagehelp = S("Lava crust is strong enough to walk on, but still hot enough to inflict burns."),
+	tiles = {
+		{
+			name="nether_lava_crust_animated.png",
+			backface_culling=true,
+			tileable_vertical=true,
+			tileable_horizontal=true,
+			align_style="world",
+			scale=2,
+			animation = {
+				type = "vertical_frames",
+				aspect_w = 32,
+				aspect_h = 32,
+				length = 1.8,
+			},
+		}
+	},
+	inventory_image = minetest.inventorycube(
+		"nether_lava_crust_animated.png^[sheet:2x48:0,0",
+		"nether_lava_crust_animated.png^[sheet:2x48:0,1",
+		"nether_lava_crust_animated.png^[sheet:2x48:1,1"
+	),
+	collision_box = {
+		type = "fixed",
+		fixed = {
+			-- Damage is calculated "starting 0.1 above feet
+			-- and progressing upwards in 1 node intervals", so
+			-- lower this node's collision box by more than 0.1
+			-- to ensure damage will be taken when standing on
+			-- the node.
+			{-0.5, -0.5, -0.5, 0.5, 0.39, 0.5}
+		},
+	},
+	selection_box = {
+		type = "fixed",
+		fixed = {
+			-- Keep the selection box matching the visual node,
+			-- rather than the collision_box.
+			{-0.5, -0.5, -0.5, 0.5, 0.5, 0.5}
+		},
+	},
+
+	after_destruct = function(pos, oldnode)
+		smash_lava_crust(pos, true)
+	end,
+	after_dig_node = function(pos, oldnode, oldmetadata, digger)
+	end,
+	on_blast = function(pos, intensity)
+		smash_lava_crust(pos, false)
+	end,
+
+	paramtype = "light",
+	light_source = default.LIGHT_MAX - 3,
+	buildable_to = false,
+	walkable_to = true,
+	is_ground_content = true,
+	drop = {
+		items = {{
+			-- Allow SilkTouch-esque "pickaxes of preservation" to mine the lava crust intact, if PR #10141 gets merged.
+			tools = {"this line will block early MT versions which don't respect the tool_groups restrictions"},
+			tool_groups = {{"pickaxe", "preservation"}},
+			items = {"nether:lava_crust"}
+		}}
+	},
+	--liquid_viscosity = 7,
+	damage_per_second = 2,
+	groups = {oddly_breakable_by_hand = 3, cracky = 3, explody = 1, igniter = 1},
+})
+
+
+-- Fumaroles (Chimney's)
+
+local function fumarole_startTimer(pos, timeout_factor)
+
+	if timeout_factor == nil then timeout_factor = 1 end
+	local next_timeout = (math.random(50, 900) / 10) * timeout_factor
+
+	minetest.get_meta(pos):set_float("expected_timeout", next_timeout)
+	minetest.get_node_timer(pos):start(next_timeout)
+end
+
+-- Create an LBM to start fumarole node timers
+minetest.register_lbm({
+	label = "Start fumarole smoke",
+	name  = "nether:start_fumarole",
+	nodenames = {"nether:fumarole"},
+	run_at_every_load = true,
+	action = function(pos, node)
+		local node_above = minetest.get_node({x = pos.x, y = pos.y + 1, z = pos.z})
+		if node_above.name == "air" then --and node.param2 % 4 == 0 then
+			fumarole_startTimer(pos)
+		end
+	end
+})
+
+local function set_fire(pos, extinguish)
+	local posBelow  = {x = pos.x, y = pos.y - 1, z = pos.z}
+
+	if extinguish then
+		if minetest.get_node(pos).name      == "fire:permanent_flame" then minetest.set_node(pos,      {name="air"}) end
+		if minetest.get_node(posBelow).name == "fire:permanent_flame" then minetest.set_node(posBelow, {name="air"}) end
+
+	elseif minetest.get_node(posBelow).name == "air" then
+		minetest.set_node(posBelow, {name="fire:permanent_flame"})
+	elseif minetest.get_node(pos).name == "air" then
+		minetest.set_node(pos, {name="fire:permanent_flame"})
+	end
+end
+
+local function fumarole_onTimer(pos, elapsed)
+
+	local expected_timeout = minetest.get_meta(pos):get_float("expected_timeout")
+	if elapsed > expected_timeout + 10 then
+		-- The timer didn't fire when it was supposed to, so the chunk was probably inactive and has
+		-- just been approached again, meaning *every* fumarole's on_timer is about to go off.
+		-- Skip this event and restart the clock for a future random interval.
+		fumarole_startTimer(pos, 1)
+		return false
+	end
+
+	-- Fumaroles in the Nether can catch fire.
+	-- (if taken to the surface and used as cottage chimneys, they don't catch fire)
+	local inNether = pos.y <= nether.DEPTH and pos.y >= nether.DEPTH_FLOOR
+	local canCatchFire = inNether and minetest.registered_nodes["fire:permanent_flame"] ~= nil
+	local smoke_offset   = 0
+	local timeout_factor = 1
+	local smoke_time_adj = 1
+
+	local posAbove = {x = pos.x, y = pos.y + 1, z = pos.z}
+	local extinguish = minetest.get_node(posAbove).name ~= "air"
+
+	if extinguish or (canCatchFire and math.floor(elapsed) % 7 == 0) then
+
+		if not extinguish then
+			-- fumarole gasses are igniting
+			smoke_offset   = 1
+			timeout_factor = 0.22 -- reduce burning time
+		end
+
+		set_fire(posAbove, extinguish)
+		set_fire({x = pos.x + 1, y = pos.y + 1, z = pos.z},     extinguish)
+		set_fire({x = pos.x - 1, y = pos.y + 1, z = pos.z},     extinguish)
+		set_fire({x = pos.x,     y = pos.y + 1, z = pos.z + 1}, extinguish)
+		set_fire({x = pos.x,     y = pos.y + 1, z = pos.z - 1}, extinguish)
+
+	elseif inNether then
+
+		if math.floor(elapsed) % 3 == 1 then
+			-- throw up some embers / lava splash
+			local embers_particlespawn_def = {
+				amount = 6,
+				time = 0.1,
+				minpos = {x=pos.x - 0.1, y=pos.y + 0.0, z=pos.z - 0.1},
+				maxpos = {x=pos.x + 0.1, y=pos.y + 0.2, z=pos.z + 0.1},
+				minvel = {x = -.5, y = 4.5, z = -.5},
+				maxvel = {x =  .5, y = 7,   z =  .5},
+				minacc = {x = 0, y = -10, z = 0},
+				maxacc = {x = 0, y = -10, z = 0},
+				minexptime = 1.4,
+				maxexptime = 1.4,
+				minsize = .2,
+				maxsize = .8,
+				texture = "^[colorize:#A00:255",
+				glow = 8
+			}
+			minetest.add_particlespawner(embers_particlespawn_def)
+			embers_particlespawn_def.texture = "^[colorize:#A50:255"
+			embers_particlespawn_def.maxvel.y = 3
+			embers_particlespawn_def.glow = 12
+			minetest.add_particlespawner(embers_particlespawn_def)
+
+		else
+			-- gas noises
+			minetest.sound_play("nether_fumarole", {
+				pos = pos,
+				max_hear_distance = 60,
+				gain = 0.24,
+				pitch = math.random(35, 95) / 100
+			})
+		end
+
+	else
+		-- we're not in the Nether, so can afford to be a bit more smokey
+		timeout_factor = 0.4
+		smoke_time_adj = 1.3
+	end
+
+	-- let out some smoke
+	minetest.add_particlespawner({
+		amount = 12 * smoke_time_adj,
+		time = math.random(40, 60) / 10 * smoke_time_adj,
+		minpos = {x=pos.x - 0.2, y=pos.y + smoke_offset, z=pos.z - 0.2},
+		maxpos = {x=pos.x + 0.2, y=pos.y + smoke_offset, z=pos.z + 0.2},
+		minvel = {x=0, y=0.7, z=-0},
+		maxvel = {x=0, y=0.8, z=-0},
+		minacc = {x=0.0,y=0.0,z=-0},
+		maxacc = {x=0.0,y=0.1,z=-0},
+		minexptime = 5,
+		maxexptime = 5.5,
+		minsize = 1.5,
+		maxsize = 7,
+		texture = "nether_smoke_puff.png",
+	})
+
+	fumarole_startTimer(pos, timeout_factor)
+	return false
+end
+
+
+minetest.register_node("nether:fumarole", {
+	description=S("Fumarolic Chimney"),
+	_doc_items_longdesc = S("A vent in the earth emitting steam and gas"),
+	_doc_items_usagehelp = S("Can be repurposed to provide puffs of smoke in a chimney"),
+	tiles = {"nether_rack.png"},
+	on_timer = fumarole_onTimer,
+	after_place_node = function(pos, placer, itemstack, pointed_thing)
+		fumarole_onTimer(pos, 1)
+		return false
+	end,
+	is_ground_content = true,
+	groups = {cracky = 3, level = 2, fumarole=1},
+	paramtype = "light",
+	drawtype = "nodebox",
+	node_box = {
+		type = "fixed",
+		fixed = {
+			{-0.5000, -0.5000, -0.5000, -0.2500, 0.5000, 0.5000},
+			{-0.5000, -0.5000, -0.5000, 0.5000, 0.5000, -0.2500},
+			{-0.5000, -0.5000, 0.2500, 0.5000, 0.5000, 0.5000},
+			{0.2500, -0.5000, -0.5000, 0.5000, 0.5000, 0.5000}
+		}
+	},
+	selection_box = {type = 'fixed', fixed = {-.5, -.5, -.5, .5, .5, .5}}
+})
+
+minetest.register_node("nether:fumarole_slab", {
+	description=S("Fumarolic Chimney Slab"),
+	_doc_items_longdesc = S("A vent in the earth emitting steam and gas"),
+	_doc_items_usagehelp = S("Can be repurposed to provide puffs of smoke in a chimney"),
+	tiles = {"nether_rack.png"},
+	is_ground_content = true,
+	on_timer = fumarole_onTimer,
+	after_place_node = function(pos, placer, itemstack, pointed_thing)
+		fumarole_onTimer(pos, 1)
+		return false
+	end,
+	groups = {cracky = 3, level = 2, fumarole=1},
+	paramtype = "light",
+	drawtype = "nodebox",
+	node_box = {
+		type = "fixed",
+		fixed = {
+			{-0.5000, -0.5000, -0.5000, -0.2500, 0.000, 0.5000},
+			{-0.5000, -0.5000, -0.5000, 0.5000, 0.000, -0.2500},
+			{-0.5000, -0.5000, 0.2500, 0.5000, 0.000, 0.5000},
+			{0.2500, -0.5000, -0.5000, 0.5000, 0.000, 0.5000}
+		}
+	},
+	selection_box = {type = 'fixed', fixed = {-.5, -.5, -.5, .5, 0, .5}},
+	collision_box = {type = 'fixed', fixed = {-.5, -.5, -.5, .5, 0, .5}}
+})
+
+minetest.register_node("nether:fumarole_corner", {
+	description=S("Fumarolic Chimney Corner"),
+	tiles = {"nether_rack.png"},
+	is_ground_content = true,
+	groups = {cracky = 3, level = 2, fumarole=1},
+	paramtype = "light",
+	paramtype2 = "facedir",
+	drawtype = "nodebox",
+	node_box = {
+		type = "fixed",
+		fixed = {
+			{-0.2500, -0.5000, 0.5000, 0.000, 0.5000, 0.000},
+			{-0.5000, -0.5000, 0.2500, 0.000, 0.5000, 0.000},
+			{-0.5000, -0.5000, 0.2500, 0.000, 0.000, -0.5000},
+			{0.000, -0.5000, -0.5000, 0.5000, 0.000, 0.5000}
+		}
+	},
+	selection_box = {
+		type = 'fixed',
+		fixed = {
+			{-.5, -.5, -.5, .5, 0, .5},
+			{0, 0, .5, -.5, .5, 0},
+		}
+	}
+
+})
+
+-- nether:airlike_darkness is an air node through which light does not propagate.
+-- Use of it should be avoided when possible as it has the appearance of a lighting bug.
+-- Fumarole decorations use it to stop the propagation of light from the lava below,
+-- since engine limitations mean any mesh or nodebox node will light up if it has lava
+-- below it.
+local airlike_darkness = {}
+for k,v in pairs(minetest.registered_nodes["air"]) do airlike_darkness[k] = v end
+airlike_darkness.paramtype = "none"
+minetest.register_node("nether:airlike_darkness", airlike_darkness)

portal_api.txt

@@ -0,0 +1,265 @@
+Portal API Reference
+====================
+
+The portal system used to get to the Nether can be used to create portals
+to other realms.
+
+Pick a node type to have your portals built from, a shape in which the
+portals must be built, and provide 3 functions for portals to find their
+destination with:
+ * `find_realm_anchorPos(surface_anchorPos)`
+ * `find_surface_anchorPos(realm_anchorPos)`
+ * `is_within_realm(pos)`
+
+Optionally decorate by choosing portal colors, particles, media etc.
+
+See `init.lua` and `portal_examples.lua` for examples of 3 different portals.
+
+Portal code is more efficient when each type of portal uses a different type
+of node to build its frame out of - consider creating your own node for
+players to build portals from. However it is possible to register more than
+one kind of portal with the same frame material — such as obsidian — provided
+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
+------
+
+This API uses the concept of a realm for each type of portal. If a portal is
+outside its realm then it links to a portal inside the realm, if a portal is
+inside its realm then it links to the outside.
+
+You get to decide what constitutes your realm by implementing the function
+`is_within_realm(position)`.
+
+For example, the Nether realm is defined as existing at a certain depth and
+anything above that depth is considered outside the Realm.
+
+In contrast, the "Surface portal" - an example in portal_examples.lua, only
+uses one realm. Its `is_within_realm()` function always returns true so that
+any time a portal is opened it will use `find_surface_anchorPos()`.
+
+Note that the name "find_surface_anchorPos" is a Nether-centric misnomer, as
+different types of portals are free to use different definitions of a realm
+such that leaving the realm might not be synonymous with travelling to the
+surface.
+
+
+Helper functions
+----------------
+
+* `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, 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
+  distance_limit.
+    * A y_factor of 0 means y does not affect the distance_limit, a y_factor
+      of 1 means y is included (the default if y_factor is nil), and a y_factor
+      of 2 would squash the search-sphere by a factor of 2 on the y-axis, etc.
+    * Only portals in the same realm as the anchorPos will be returned, even if
+      y_factor is 0.
+    * Pass a nil (or negative) distance_limit to indicate no distance limit
+
+
+API functions
+-------------
+
+Call these functions only at load time:
+
+* `nether.register_portal(name, portal_definition)`
+    * Returns true on success. Can return false if the portal definition
+      clashes with a portal already registered by another mod, e.g. if the size
+      and frame node is not unique.
+      A false return value should be handled, you could:
+        * Fall back to using a secondary material for portals to be built with.
+        * Use error() to exit lua with a message explaining how two mods are
+          clashing and how it can be resolved.
+        * Continue without a portal (the reason will be logged for the user).
+* `nether.register_portal_ignition_item(name, ignition_failure_sound)`
+    * ignition_failure_sound is optional, it plays any time an attempt to use
+      the item occurs if a portal is not ignited.
+* `nether.register_wormhole_node(name, nodedef_overrides)`
+    * Can be used to register wormhole nodes with a different post_effect_color
+      from the "nether:portal" node. "Post effect color" is the tint the world
+      takes on when you are standing inside a portal. `post_effect_color` is the
+      only key/value that is needed in the nodedef_overrides table to achieve that,
+      but the function allows any nodedef key/value to be specified/overridden.
+    * After `register_wormhole_node()`, invoke `register_portal()` and include
+      `wormhole_node_name` in the portal_definition, assigning it the name of the
+      new wormhole node.
+* `nether.unregister_portal(name)`
+    * Unregisters the portal from the engine, and deletes the entry with key
+      `name` from `nether.registered_portals` and associated internal tables.
+    * Returns true on success
+    * You will probably never need to call this, it exists only for completeness.
+
+
+Portal definition
+-----------------
+
+Used by `nether.register_portal`.
+
+    {
+        frame_node_name     = "default:obsidian",
+        -- 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:
+        --     nether.PortalShape_Traditional (default)
+        --     nether.PortalShape_Circular
+        --     nether.PortalShape_Platform
+        -- New shapes can be created, but are beyond the scope of this guide.
+
+        wormhole_node_name  = "nether: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.
+        -- A value from 0 to 7 corresponding to the color of pixels in
+        -- nether_portals_palette.png:
+        --     0 traditional/magenta
+        --     1 black
+        --     2 blue
+        --     3 green
+        --     4 cyan
+        --     5 red
+        --     6 yellow
+        --     7 white
+
+        particle_color      = "#808",
+        -- Optional. Will default to a colour matching the wormhole_node_color
+        -- if not specified.
+
+        particle_texture    = "image.png",
+        -- Optional. Hardware colouring (i.e. particle_color) is applied to
+        -- this texture, use particle_texture_colored instead if you want to
+        -- use the colors of the image.
+        -- Animation and particle scale may also be specified, e.g:
+        -- particle_texture = {
+        --      name = "nether_particle_anim1.png",
+        --      animation = {
+        --          type = "vertical_frames",
+        --          aspect_w = 7,
+        --          aspect_h = 7,
+        --          length = 1,
+        --      },
+        --      scale = 1.5
+        --  },
+        -- See lua_api.txt for Tile Animation definition
+        -- Some animated and non-animated textures are provided by this mod:
+        --     nether_particle.png          (original)
+        --     nether_particle_anim1.png    (stars)
+        --     nether_particle_anim2.png    (bubbles)
+        --     nether_particle_anim3.png    (sparks)
+        --     nether_particle_anim4.png    (particles)
+
+        title = "Gateway to Moria",
+        -- Optional. Provides a title for the portal.
+        -- Used in the Book of Portals or Help modpack.
+
+        book_of_portals_pagetext = "Everything I need the player to know",
+        -- Optional. Provides the text for the portal in the Book of Portals
+        -- and Help modpack.
+        -- The Book of Portals is a book that can be found in chests, and
+        -- provides players with instructions on how to build and use the
+        -- portal, so be sure to mention the node type the frame must be built
+        -- from.
+        -- This can also provide flavortext or details about where the portal
+        -- will take the player.
+
+        sounds = {
+            ambient    = <SimpleSoundSpec>,
+            -- if the ambient SimpleSoundSpec is a table it can also contain a
+            -- "length" int, which is the number of seconds to wait before
+            -- repeating the ambient sound. Default is 3.
+            ignite     = <SimpleSoundSpec>,
+            extinguish = <SimpleSoundSpec>,
+            teleport   = <SimpleSoundSpec>,
+        }
+        -- sounds is optional
+
+        within_realm = function(pos),
+        -- Required. Return true if a portal at pos is in the realm, rather
+        -- than the surface world.
+        -- Ideally implementations are fast, as this function can be used to
+        -- sift through a list of portals.
+
+        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)
+        -- If orientation is not specified then the orientation of the surface
+        -- portal will be used.
+        -- 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, player_name),
+        -- Optional. If you don't implement this then a position near the
+        -- surface will be picked.
+        -- Return an anchorPos or (anchorPos, orientation)
+        -- The name of this function is a Nether-centric misnomer. It should
+        -- return a position outside the realm, and different types of portals
+        -- are free to use different definitions of a realm such that leaving
+        -- the realm might not be synonymous with travelling to the surface.
+        -- If orientation is not specified then the orientation of the realm
+        -- portal will be used.
+        -- 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),
+        -- invoked once per second per portal
+        on_extinguish        = function(portalDef, anochorPos, 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)
+        -- invoked when a player or mesecon ignites a portal
+        on_created           = function(portalDef, anochorPos, 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

@@ -0,0 +1,320 @@
+--[[
+
+  Nether mod portal examples for Minetest
+
+  These portal API examples work independently of the Nether realm
+  and Nether portal. To try these examples, enable them in:
+	  Minetest -> Settings -> All settings -> Mods -> nether
+  Once enabled, details on how to build them can be found in dungeon
+  chests in the book of portals.
+
+  --
+
+  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.
+
+]]--
+local S = nether.get_translator
+
+
+local ENABLE_PORTAL_EXAMPLE_FLOATLANDS    = false
+local ENABLE_PORTAL_EXAMPLE_SURFACETRAVEL = false
+
+-- Sets how far a Surface Portal will travel, measured in cells along the Moore curve,
+-- which are about 117 nodes square each. Larger numbers will generally mean further distance
+-- as-the-crow-flies, but this will not always be true due to the how the Moore curve
+-- frequently doubles back upon itself.
+-- This doubling-back prevents the surface portal from taking players easily accross the
+-- map - the curve is 262144 cells long!
+local SURFACE_TRAVEL_DISTANCE = 26
+
+
+--=================================================--
+-- Portal to the Floatlands, playable code example --
+--==================================================--
+local FLOATLANDS_ENABLED
+local FLOATLAND_LEVEL    = 1280
+
+if minetest.settings:get_bool("nether_enable_portal_example_floatlands", ENABLE_PORTAL_EXAMPLE_FLOATLANDS) or ENABLE_PORTAL_EXAMPLE_FLOATLANDS then
+
+	local floatlands_flavortext = ""
+	if minetest.get_mapgen_setting("mg_name") == "v7" then
+		local mgv7_spflags = minetest.get_mapgen_setting("mgv7_spflags")
+		FLOATLANDS_ENABLED = mgv7_spflags ~= nil and mgv7_spflags:find("floatlands") ~= nil and mgv7_spflags:find("nofloatlands") == nil
+		FLOATLAND_LEVEL = minetest.get_mapgen_setting("mgv7_floatland_level") or 1280
+
+		if FLOATLANDS_ENABLED then
+			floatlands_flavortext = "\n\n	" .. S("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.")
+		end
+	end
+
+
+	nether.register_portal("floatlands_portal", {
+		shape               = nether.PortalShape_Platform,
+		frame_node_name     = "default:ice",
+		wormhole_node_color = 7, -- 7 is white
+		particle_texture    = {
+			name      = "nether_particle_anim1.png",
+			animation = {
+				type = "vertical_frames",
+				aspect_w = 7,
+				aspect_h = 7,
+				length = 1,
+			},
+			scale = 1.5
+		},
+		title = S("Floatlands Portal"),
+		book_of_portals_pagetext = S([[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.
+
+This 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]],
+		floatlands_flavortext),
+
+		is_within_realm = function(pos) -- return true if pos is inside the Nether
+			return pos.y > FLOATLAND_LEVEL - 200
+		end,
+
+		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}
+
+			-- a y_factor of 0 makes the search ignore the altitude of the portals (as long as they are in the Floatlands)
+			local existing_portal_location, existing_portal_orientation = nether.find_nearest_working_portal("floatlands_portal", destination_pos, 10, 0)
+			if existing_portal_location ~= nil then
+				return existing_portal_location, existing_portal_orientation
+			else
+				return destination_pos
+			end
+		end
+	})
+
+end
+
+
+--==============================================--
+-- Surface-travel portal, playable code example --
+--==============================================--
+
+-- These Moore Curve functions requred 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
+
+if minetest.settings:get_bool("nether_enable_portal_example_surfacetravel", ENABLE_PORTAL_EXAMPLE_SURFACETRAVEL) or ENABLE_PORTAL_EXAMPLE_SURFACETRAVEL then
+
+	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.
+
+These 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.
+
+Due 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.]]),
+
+		is_within_realm = function(pos)
+			-- Always return true, because these portals always just take you around the surface
+			-- rather than taking you to a different realm
+			return true
+		end,
+
+		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, 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.
+
+			local cellCount = 512
+			local maxDistFromOrigin = 30000 -- the world edges are at X=30927, X=−30912, Z=30927 and Z=−30912
+
+			-- clip realm_anchorPos to maxDistFromOrigin, and move the origin so that all values are positive
+			local x = math.min(maxDistFromOrigin, math.max(-maxDistFromOrigin, realm_anchorPos.x)) + maxDistFromOrigin
+			local z = math.min(maxDistFromOrigin, math.max(-maxDistFromOrigin, realm_anchorPos.z)) + maxDistFromOrigin
+
+			local divisor = math.ceil(maxDistFromOrigin * 2 / cellCount)
+			local distance = get_moore_distance(cellCount, math.floor(x / divisor + 0.5), math.floor(z / divisor + 0.5))
+			local destination_distance = (distance + SURFACE_TRAVEL_DISTANCE) % (cellCount * cellCount)
+			local moore_pos = get_moore_coords(cellCount, destination_distance)
+			local target_x = moore_pos.x * divisor - maxDistFromOrigin
+			local target_z = moore_pos.y * divisor - maxDistFromOrigin
+
+			local search_radius = divisor / 2 - 5 -- any portal within this area will do
+
+			-- a y_factor of 0 makes the search ignore the altitude of the portals
+			local existing_portal_location, existing_portal_orientation =
+				nether.find_nearest_working_portal("surface_portal", {x = target_x, y = 0, z = target_z}, search_radius, 0)
+
+			if existing_portal_location ~= nil then
+				-- use the existing portal that was found near target_x, target_z
+				return existing_portal_location, existing_portal_orientation
+			else
+				-- find a good location for the new portal, or if that isn't possible then at
+				-- least adjust the coords a little so portals don't line up in a grid
+				local adj_x, adj_z = 0, 0
+
+				-- Deterministically look for a location in the cell where get_spawn_level() can give
+				-- us a surface height, since nether.find_surface_target_y() works *much* better when
+				-- it can use get_spawn_level()
+				local prng = PcgRandom( -- seed the prng so that all portals for these Moore Curve coords will use the same random location
+					moore_pos.x * 65732 +
+					moore_pos.y * 729   +
+					minetest.get_mapgen_setting("seed") * 3
+				)
+
+				local attemptLimit = 15 -- how many attempts we'll make at finding a good location
+				for attempt = 1, attemptLimit do
+					adj_x = math.floor(prng:rand_normal_dist(-search_radius, search_radius, 2) + 0.5)
+					adj_z = math.floor(prng:rand_normal_dist(-search_radius, search_radius, 2) + 0.5)
+					if minetest.get_spawn_level == nil or minetest.get_spawn_level(target_x + adj_x, target_z + adj_z)	~= nil then
+						-- Found a location which will be at ground level - unless a player has built there.
+						-- Or this is MT 0.4 which does not have get_spawn_level(), so there's no point looking
+						-- at any further further random locations.
+						break
+					end
+				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", player_name)
+
+				return destination_pos
+			end
+		end
+	})
+
+end
+
+--=========================================--
+-- Hilbert curve and Moore curve functions --
+--=========================================--
+
+-- These are space-filling curves, used by the surface_portal example as a way to determine where
+-- to place portals. https://en.wikipedia.org/wiki/Moore_curve
+
+
+-- Flip a quadrant on a diagonal axis
+-- cell_count is the number of cells across the square is split into, and must be a power of 2
+-- if flip_twice is true then pos does not change (even numbers of flips cancel out)
+-- if flip_direction is true then the position is flipped along the \ diagonal
+-- if flip_direction is false then the position is flipped along the / diagonal
+local function hilbert_flip(cell_count, pos, flip_direction, flip_twice)
+	if not flip_twice then
+		if flip_direction then
+			pos.x = (cell_count - 1) - pos.x;
+			pos.y = (cell_count - 1) - pos.y;
+		end
+
+		local temp_x = pos.x;
+		pos.x = pos.y;
+		pos.y = temp_x;
+	end
+end
+
+local function test_bit(cell_count, value, flag)
+	local bit_value = cell_count / 2
+	while bit_value > flag and bit_value >= 1  do
+		if value >= bit_value then value = value - bit_value end
+		bit_value = bit_value / 2
+	end
+	return value >= bit_value
+end
+
+-- Converts (x,y) to distance
+-- starts at bottom left corner, i.e. (0, 0)
+-- ends at bottom right corner, i.e. (cell_count - 1, 0)
+local function get_hilbert_distance (cell_count, x, y)
+	local distance = 0
+	local pos = {x=x, y=y}
+	local rx, ry
+
+	local s = cell_count / 2
+	while s > 0 do
+
+		if test_bit(cell_count, pos.x, s) then rx = 1 else rx = 0 end
+		if test_bit(cell_count, pos.y, s) then ry = 1 else ry = 0 end
+
+		local rx_XOR_ry = rx
+		if ry == 1 then rx_XOR_ry = 1 - rx_XOR_ry end -- XOR'd ry against rx
+
+		distance = distance + s * s * (2 * rx + rx_XOR_ry)
+		hilbert_flip(cell_count, pos, rx > 0, ry > 0);
+
+		s = math.floor(s / 2)
+	end
+	return distance;
+end
+
+-- Converts distance to (x,y)
+local function get_hilbert_coords(cell_count, distance)
+	local pos = {x=0, y=0}
+	local rx, ry
+
+	local s = 1
+	while s < cell_count do
+		rx = math.floor(distance / 2) % 2
+		ry = distance % 2
+		if rx == 1 then ry = 1 - ry end -- XOR ry with rx
+
+		hilbert_flip(s, pos, rx > 0, ry > 0);
+		pos.x = pos.x + s * rx
+		pos.y = pos.y + s * ry
+		distance = math.floor(distance / 4)
+
+		s = s * 2
+	end
+	return pos
+end
+
+
+-- Converts (x,y) to distance
+-- A Moore curve is a variation of the Hilbert curve that has the start and
+-- end next to each other.
+-- Top middle point is the start/end location
+get_moore_distance = function(cell_count, x, y)
+
+	local quadLength = cell_count / 2
+	local quadrant = 1 - math.floor(y / quadLength)
+	if math.floor(x / quadLength) == 1 then quadrant = 3 - quadrant end
+	local flipDirection = x < quadLength
+
+	local pos = {x = x % quadLength, y = y % quadLength}
+	hilbert_flip(quadLength, pos, flipDirection, false)
+
+	return (quadrant * quadLength * quadLength) + get_hilbert_distance(quadLength, pos.x, pos.y)
+end
+
+
+-- Converts distance to (x,y)
+-- A Moore curve is a variation of the Hilbert curve that has the start and
+-- end next to each other.
+-- Top middle point is the start/end location
+get_moore_coords = function(cell_count, distance)
+	local quadLength = cell_count / 2
+	local quadDistance = quadLength * quadLength
+	local quadrant = math.floor(distance / quadDistance)
+	local flipDirection = distance * 2 < cell_count * cell_count
+	local pos = get_hilbert_coords(quadLength, distance % quadDistance)
+	hilbert_flip(quadLength, pos, flipDirection, false)
+
+	if quadrant >= 2     then pos.x = pos.x + quadLength end
+	if quadrant % 3 == 0 then pos.y = pos.y + quadLength end
+
+	return pos
+end

settingtypes.txt

@@ -0,0 +1,25 @@
+# Travelling a short distance in the Nether can correspond to a much further distance on the surface.
+#
+# A factor of 10 might be a better value for Minetest, since there's no sprint, but ex-Minecraft players will be mathing for 8.
+nether_fasttravel_factor (Nether fast-travel factor) int 8
+
+# The likelyhood of finding a Book containing all the portal plans in a dungeon chest. 
+# Set to 0 to disable, or 10 to have it extremely common.
+#
+# (This value will be treated as 0 when the Nether portal is the only type of portal available, or when the help modpack is installed)
+nether_portalBook_loot_weighting (Likelyhood of finding Book of Portals in dungeon chests) int 9
+
+# Turn off to disable the Nether and Nether portal
+nether_realm_enabled (Enable Nether realm & portal) bool true
+
+# Enables the Floatlands portal api code example
+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 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 +1,138 @@
+--[[
+
+  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"),
+	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]=0.4}, uses=35, maxlevel=3},
+		},
+		damage_groups = {fleshy=4},
+	},
+	sound = {breaks = "default_tool_breaks"},
+	groups = {pickaxe = 1}
+})
+
+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"}
+	}
+})