Primordial cavern layer (#12)

* bring in the art assets from ClockGen's "better_caves_modpack" under CC BY 4.0,, code written from scratch.

* update mapgen_helper

* import ClockGen's giant mushroom schematics, make them and giant ferns growable

* add giant jungle mushroom, rough out actual cavern layer code framework

* fungal ceiling decorations

* decorate fungal floor a bit

* update mapgen_helper

* update primordial mushroom schematic placement to ensure it fits

* add giant mycelium fungoidal structure

* add giant mycelium to mapgen

* fix settings for giant mycelium

* make mycelium grow when players aren't present

* allow mycelium growth to pause when it hits unloaded areas

* add a use for giant mycelium

* make giant mushrooms edible, make jungle trees growable

* rough out the jungle biome

* Make a spectrum of jungle growth

* optimize pngs, add is_ground_content to everything

* use custom is_ground_content method

* fix a crash with veinstone, and simplify nvals_cave lookup now that overgen covers the same area

* more fixes for overgen support

* remove unintentional airspace from underside of slade

* fix for overgen crash in level 2

* primordial column material, add sealed shafts to underworld

* add seal block

* Set up puzzle seals to be able to dig a staircase shaft through the slade layer. TODO: the puzzle to guard the trigger.

* puzzle seals now fully functional. Need to add clues for decoding the keys next.

* add a small bit of anti-griefing - the seal breach bell only tolls globally 13 times per activation

* add flowers to the underworld warrior bones

* switch to a different key bell

* fancy up the puzzle seal temples with some custom blocks, add sub-slade grid passages

* add a clue to the seal formspec

* tweak background of inscription 2 so it's less obviously a copy of the background for inscription 1

* switch to compositing to save a few bytes

* fancy up the seal's upper surface with inscriptions to make the formspec feel consistent

* puzzle particle, bones were only spawning on top of structures

* fix ice/oil on level 3, tweak some loot probabilities

* add trail mod support

* remove deprecated files

* boost default plant growth delay, add growing selection boxes

* update map colours

* add named waypoints to the underworld

* try a more efficient way of changing the interiors of columns

* polishing up the Primordial layer

* update guide with some Primordial teasers

* updated magma sea screenshot

* update mapgen_helper and subterrane

* reduce density of megaflora a bit - was too hard to walk through

* spreading_dirt_type depends on light, create my own ABM instead

* add names to the glowing pits and some of the ruins

* separate setting for ruin markers

* record identity of slade-breachers

* make mycelia climbable

* update subterrane

* change surface tunnel detection to allow above-ground stalactites and stalagmites

* add rare thicker Goblin Caps, suitable for use as huts.

* better goblin cap schematics

* update colours

* make it slightly harder to dig down through amethyst sheathing of pits

* fixing up fungus light sensitivity, tree growth code

* fix a few minor bugs

* update deprecated functions

* add various eating sounds

* make mapping kit requirement more flexible

* update spindlestem growth code, remove deprecated functions

* fix leftover undefined variable

* add fireflies to primordial, spread out the post-mapgen node timer for plant matter a bit more.

* fix bones formspec

* add lbm to upgrade old bones

* fix slade undiggability

* make torchspines smokey and manually lightable

* fix drop definitions

* generate dry stalactites in near-surface caverns.

* caverns become far too smokey, alas

* add pitter patter of spore tree spores, alternate paper recipe

* new mapgen_helper metrics

* add smokey back to torchspine now that it can be dialed down a bit

* replace glowstone texture with a new animated one

* switch from ABM to node timer for mapgen mycelium growth

* make mapgen mycelium timer delay configurable

* improve the efficiency of giant mycelium growth using flat node array, fewer dereferences

* remove the smoke from torchspines again - it doesn't dissipate that deep underground

* give slade a more muted, gloomy hue to differentiate it from nether stone

* update screenshots with new slade colors

* update mapgen_helper

df_caverns/shared.lua

@@ -124,6 +124,9 @@ local content_in_list=function(content, list)
 end
 
 df_caverns.tunnel_floor = function(minp, maxp, area, vi, nvals_cracks, data, data_param2, wet)
+	if maxp.y > -30 then
+		wet = false
+	end
 	local ystride = area.ystride
 	local index2d = mapgen_helper.index2di(minp, maxp, area, vi)
 	local cracks = nvals_cracks[index2d]
@@ -148,6 +151,10 @@ df_caverns.tunnel_floor = function(minp, maxp, area, vi, nvals_cracks, data, dat
 end
 
 df_caverns.tunnel_ceiling = function(minp, maxp, area, vi, nvals_cracks, data, data_param2, wet)
+	if maxp.y > -30 then
+		wet = false
+	end
+
 	local ystride = area.ystride
 	local index2d = mapgen_helper.index2di(minp, maxp, area, vi)
 	local cracks = nvals_cracks[index2d]
@@ -207,4 +214,37 @@ df_caverns.place_shrub = function(vi, area, data, param2_data, shrub_list)
 	
 	local shrub = shrub_list[math.random(#shrub_list)]
 	shrub(vi, area, data, param2_data)
+end
+
+---------------------------------------------------------------------------------
+-- This method allows subterrane to overgenerate caves without destroying any of the decorations
+local dfcaverns_nodes = nil
+local dfcaverns_mods = {
+	"df_farming:",
+	"df_mapitems:",
+	"df_primordial_items:",
+	"df_trees:",
+	"df_underworld_items:",
+	"ice_sprites:",
+	"mine_gas:",
+}
+df_caverns.is_ground_content = function(c_node)
+	if dfcaverns_nodes then
+		return not dfcaverns_nodes[c_node]
+	end
+	dfcaverns_nodes = {}
+	for k, v in pairs(minetest.registered_nodes) do
+		for _, prefix in ipairs(dfcaverns_mods) do
+			if k:sub(1, #prefix) == prefix then
+				dfcaverns_nodes[minetest.get_content_id(k)] = true
+			end
+		end
+	end
+	dfcaverns_nodes[minetest.get_content_id("default:ice")] = true -- needed for nethercap cavern water covering
+	dfcaverns_nodes[minetest.get_content_id("oil:oil_source")] = true -- needed for blackcap oil slicks
+	if minetest.get_modpath("fireflies") then
+		dfcaverns_nodes[minetest.get_content_id("fireflies:firefly")] = true -- used in the primordial caverns
+	end
+	dfcaverns_mods = nil
+	return not dfcaverns_nodes[c_node]
 end