Small stuff (#8)

* cave pearls and spindleshrooms (name subject to change) now are things. Not in mapgen yet.

* add the wandering "gas wisp" to light up some of the gas-filled caverns

* make wisps rarely spawned by gas explosions

* revamp spindlestems into a sort of mineral detector, add glowing extract bottles

* optimize pngs

* add gas wisps to mapgen

* add spindlestems to cavern level 1, most level 1 warrens are now lit up

* update internal names, adjust mineral detection range

* add cave pearls to some level 2 warrens and tunnels

* switch experimental simplecrafting_lib support to crafting mod

* Pearls don't grow on falling nodes

* put spindlestems with goblin caps, make them always grow red when near those

* bunch of documentation

* add castle coral to replace cave coral, which has been repurposed into column decoration

* documentation for cave coral, update some locale text

* add a recipe for cooking oil into paraffin

* add old bones to the underworld

* MIT license for bones_loot

* also cook black cap gills into paraffin, they're oily

* add salt crystals to the bloodthorn caverns, illuminating the floor

* documentation for salt crystals

* auto-generate minetestmapper colors.

need to update the spindlestem colours manually

* add spindlestem to fungiwood caverns too, and increase warren coverage

* in anticipation of eventually adding stuff below the Slade, making glowing pit erosion self-limiting.

* add a bit of displacement to the underside of the slade layer

* Unique images and names for cooking recipes.

* revamp bones loot

* add softer footsteps for some fungus types

* update mapgen_helper

* update cave coral screenshot

* mention glowing salts in bloodthorn caverns

df_caverns/level2.lua

@@ -18,6 +18,8 @@ local wall_vein_perlin_params = {
 	flags = "eased",
 }
 
+local c_pearls = minetest.get_content_id("df_mapitems:cave_pearls")
+
 local subsea_level = df_caverns.config.level2_min - (df_caverns.config.level2_min - df_caverns.config.level1_min) * 0.33 -- "sea level" for the flooded caverns.
 local flooding_threshold = math.min(df_caverns.config.tunnel_flooding_threshold, df_caverns.config.cavern_threshold) -- cavern value out to which we're flooding tunnels and warrens
 
@@ -60,6 +62,8 @@ if minetest.get_modpath("df_farming") then
 	}
 end
 
+local c_red = minetest.get_content_id("df_trees:spindlestem_cap_red")
+
 local goblin_cap_cavern_floor = function(abs_cracks, vert_rand, vi, area, data, data_param2)
 	local ystride = area.ystride
 	if abs_cracks < 0.1 then
@@ -72,6 +76,8 @@ local goblin_cap_cavern_floor = function(abs_cracks, vert_rand, vi, area, data,
 		end
 		if math.random() < 0.1 then
 			df_caverns.place_shrub(vi+ystride, area, data, data_param2, goblin_cap_shrublist)
+		elseif math.random() < 0.02 then
+			df_trees.spawn_spindlestem_vm(vi+ystride, area, data, data_param2, c_red)
 		elseif math.random() < 0.015 then
 			df_trees.spawn_goblin_cap_vm(vi+ystride, area, data)
 		end
@@ -243,21 +249,32 @@ local decorate_level_2 = function(minp, maxp, seed, vm, node_arrays, area, data)
 		local index2d = mapgen_helper.index2di(minp, maxp, area, vi)
 		local biome_name = get_biome(heatmap[index2d], humiditymap[index2d])
 		local flooded_caverns = nvals_cave[cave_area:transform(area, vi)] < 0 -- this indicates if we're in the "flooded" set of caves or not.
+		local ystride = area.ystride
 
 		if not (flooded_caverns and minp.y < subsea_level and area:get_y(vi) < subsea_level) then
-			if flooded_caverns or biome_name ~= "barren" then		
+			if flooded_caverns or biome_name ~= "barren" then
 				-- we're in flooded areas or are not barren
 				df_caverns.tunnel_ceiling(minp, maxp, area, vi, nvals_cracks, data, data_param2, true)
 			else
 				df_caverns.tunnel_ceiling(minp, maxp, area, vi, nvals_cracks, data, data_param2, false)
 			end
+			if not flooded_caverns and (biome_name == "barren" or biome_name == "sporetree") and nvals_cracks[index2d] > 0.5 then
+				for i= 1, 4 do
+					if math.random() > 0.5 then
+						local index = vi-i*ystride
+						if data[index] == c_air then
+							df_mapitems.place_against_surface_vm(c_pearls, index, area, data, data_param2)
+						end
+					end
+				end
+			end
 		else
 			-- air pockets
 			local ystride = area.ystride
 			local cracks = nvals_cracks[index2d]
-			if cracks > 0.5 and data[vi-ystride] == c_water then
+			if cracks > 0.4 and data[vi-ystride] == c_water then
 				data[vi-ystride] = c_air
-				if cracks > 0.7 and data[vi-ystride*2] == c_water then
+				if cracks > 0.6 and data[vi-ystride*2] == c_water then
 					data[vi-ystride*2] = c_air
 				end
 			end			
@@ -289,6 +306,7 @@ local decorate_level_2 = function(minp, maxp, seed, vm, node_arrays, area, data)
 		local index2d = mapgen_helper.index2di(minp, maxp, area, vi)
 		local biome_name = get_biome(heatmap[index2d], humiditymap[index2d])
 		local flooded_caverns = nvals_cave[cave_area:transform(area, vi)] < 0 -- this indicates if we're in the "flooded" set of caves or not.
+		local ystride = area.ystride
 
 		if not (flooded_caverns and minp.y < subsea_level and area:get_y(vi) < subsea_level) then
 			if flooded_caverns or biome_name ~= "barren" then		
@@ -297,8 +315,28 @@ local decorate_level_2 = function(minp, maxp, seed, vm, node_arrays, area, data)
 			else
 				df_caverns.tunnel_ceiling(minp, maxp, area, vi, nvals_cracks, data, data_param2, false)
 			end
+
+			if not flooded_caverns and (biome_name == "barren" or biome_name == "sporetree") and nvals_cracks[index2d] > 0.5 then
+				for i= 1, 4 do
+					if math.random() > 0.5 then
+						local index = vi-i*ystride
+						if data[index] == c_air then
+							df_mapitems.place_against_surface_vm(c_pearls, index, area, data, data_param2)
+						end
+					end
+				end
+			end
+		else
+			-- air pockets
+			local cracks = nvals_cracks[index2d]
+			if cracks > 0.4 and data[vi-ystride] == c_water then
+				data[vi-ystride] = c_air
+				if cracks > 0.6 and data[vi-ystride*2] == c_water then
+					data[vi-ystride*2] = c_air
+				end
+			end			
 		end
-		-- else air pockets?
+
 	end
 
 	----------------------------------------------