Generate netherrack under the bedrock ceiling

this is a somewhat ugly hack that uses minetest.generate_decorations
which generates decorations regardless of biome so additional steps
had to be taken to ensure no other decorations "spill over" due to
this.

mods/CORE/mcl_init/init.lua

@@ -138,6 +138,7 @@ mcl_vars.mg_nether_min = -29067 -- Carefully chosen to be at a mapchunk border
 mcl_vars.mg_nether_max = mcl_vars.mg_nether_min + 128
 mcl_vars.mg_bedrock_nether_bottom_min = mcl_vars.mg_nether_min
 mcl_vars.mg_bedrock_nether_top_max = mcl_vars.mg_nether_max
+mcl_vars.mg_nether_deco_max = mcl_vars.mg_nether_max -11 -- this is so ceiling decorations don't spill into other biomes as bedrock generation calls minetest.generate_decorations to put netherrack under the bedrock
 if not superflat then
 	mcl_vars.mg_bedrock_nether_bottom_max = mcl_vars.mg_bedrock_nether_bottom_min + 4
 	mcl_vars.mg_bedrock_nether_top_min = mcl_vars.mg_bedrock_nether_top_max - 4

mods/MAPGEN/mcl_biomes/init.lua

@@ -1531,6 +1531,23 @@ local function register_dimension_biomes()
 	--[[ REALMS ]]
 
 	--[[ THE NETHER ]]
+	-- the following decoration is a hack to cover exposed bedrock in netherrack - be careful not to put any ceiling decorations in a way that would apply to this (they would get generated regardless of biome)
+	minetest.register_decoration({
+		deco_type = "simple",
+		place_on = {"mcl_core:bedrock"},
+		sidelen = 16,
+		fill_ratio = 10,
+		biomes = { "Nether" },
+		y_min = mcl_vars.mg_lava_nether_max,
+		y_max = mcl_vars.mg_nether_max + 15,
+		height = 6,
+		max_height = 10,
+		decoration = "mcl_nether:netherrack",
+		flags = "all_ceilings",
+		param2 = 0,
+	})
+
+
 	minetest.register_biome({
 		name = "Nether",
 		node_filler = "mcl_nether:netherrack",
@@ -1554,7 +1571,7 @@ local function register_dimension_biomes()
 		fill_ratio = 10,
 		biomes = { "Nether" },
 		y_min = -31000,
-		y_max = mcl_vars.mg_nether_max,
+		y_max = mcl_vars.mg_nether_deco_max,
 		decoration = "mcl_nether:netherrack",
 		flags = "all_floors",
 		param2 = 0,
@@ -1583,7 +1600,7 @@ local function register_dimension_biomes()
 		fill_ratio = 10,
 		biomes = { "SoulsandValley" },
 		y_min = -31000,
-		y_max = mcl_vars.mg_nether_max,
+		y_max = mcl_vars.mg_nether_deco_max,
 		decoration = "mcl_blackstone:soul_soil",
 		flags = "all_floors, all_ceilings",
 		param2 = 0,
@@ -1598,7 +1615,7 @@ local function register_dimension_biomes()
 		clust_size     = 15,
 		biomes = { "SoulsandValley" },
 		y_min = mcl_vars.mg_nether_min,
-		y_max = mcl_vars.mg_nether_max + 80,
+		y_max = mcl_vars.mg_nether_deco_max,
 		noise_params = {
 			offset  = 0,
 			scale   = 1,
@@ -1633,7 +1650,7 @@ local function register_dimension_biomes()
 		fill_ratio = 10,
 		biomes = { "CrimsonForest" },
 		y_min = -31000,
-		y_max = mcl_vars.mg_nether_max,
+		y_max = mcl_vars.mg_nether_deco_max,
 		decoration = "mcl_crimson:crimson_nylium",
 		flags = "all_floors",
 		param2 = 0,
@@ -1660,7 +1677,7 @@ local function register_dimension_biomes()
 		fill_ratio = 10,
 		biomes = { "WarpedForest" },
 		y_min = -31000,
-		y_max = mcl_vars.mg_nether_max,
+		y_max = mcl_vars.mg_nether_deco_max,
 		decoration = "mcl_crimson:warped_nylium",
 		flags = "all_floors",
 		param2 = 0,
@@ -1688,7 +1705,7 @@ local function register_dimension_biomes()
 		fill_ratio = 10,
 		biomes = { "BasaltDelta" },
 		y_min = -31000,
-		y_max = mcl_vars.mg_nether_max,
+		y_max = mcl_vars.mg_nether_deco_max,
 		decoration = "mcl_blackstone:basalt",
 		flags = "all_floors",
 		param2 = 0,
@@ -1703,7 +1720,7 @@ local function register_dimension_biomes()
 	clust_size     = 20,
 	biomes = { "BasaltDelta" },
 	y_min = mcl_vars.mg_nether_min,
-	y_max = mcl_vars.mg_nether_max + 80,
+	y_max = mcl_vars.mg_nether_deco_max,
 	noise_params = {
 		offset  = 0,
 		scale   = 1,
@@ -4903,7 +4920,7 @@ local function register_dimension_decorations()
 		fill_ratio = 0.063,
 		biomes = {"CrimsonForest"},
 		y_min = mcl_vars.mg_lava_nether_max + 1,
-		y_max = mcl_vars.mg_nether_max -5,
+		y_max = mcl_vars.mg_nether_deco_max,
 		flags = "all_ceilings",
 		height = 2,
 		height_max = 8,

mods/MAPGEN/mcl_mapgen_core/api.lua

@@ -15,7 +15,7 @@ minetest.register_on_generated(function(minp, maxp, blockseed)
 	local t1 = os.clock()
 	local p1, p2 = {x=minp.x, y=minp.y, z=minp.z}, {x=maxp.x, y=maxp.y, z=maxp.z}
 	if lvm > 0 then
-		local lvm_used, shadow, deco_used = false, false, false
+		local lvm_used, shadow, deco_used, deco_table = false, false, false, false
 		local lb2 = {} -- param2
 		local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
 		local e1, e2 = {x=emin.x, y=emin.y, z=emin.z}, {x=emax.x, y=emax.y, z=emax.z}
@@ -35,7 +35,9 @@ minetest.register_on_generated(function(minp, maxp, blockseed)
 				if shadow0 then
 					shadow = true
 				end
-				if deco then
+				if deco and type(deco) == "table" then
+					deco_table = deco
+				elseif deco then
 					deco_used = true
 				end
 			end
@@ -47,7 +49,9 @@ minetest.register_on_generated(function(minp, maxp, blockseed)
 			if param2 > 0 then
 				vm:set_param2_data(data2)
 			end
-			if deco_used then
+			if deco_table then
+				minetest.generate_decorations(vm,vector.new(minp.x,deco_table.min,minp.z),vector.new(maxp.x,deco_table.max,maxp.z))
+			elseif deco_used then
 				minetest.generate_decorations(vm)
 			end
 			vm:calc_lighting(p1, p2, shadow)

mods/MAPGEN/mcl_mapgen_core/init.lua

@@ -325,8 +325,11 @@ local function world_structure(vm, data, data2, emin, emax, area, minp, maxp, bl
 			lvm_used = set_layers(data, area, c_nether_lava, c_air, mcl_vars.mg_nether_min, mcl_vars.mg_lava_nether_max, minp, maxp, lvm_used, pr)
 		end
 	end
-
-	return lvm_used, lvm_used
+	local deco = false
+	if minp.y >  mcl_vars.mg_nether_deco_max - 64 and maxp.y <  mcl_vars.mg_nether_max + 128 then
+		deco = {min=mcl_vars.mg_nether_deco_max,max=mcl_vars.mg_nether_max}
+	end
+	return lvm_used, lvm_used, deco
 end
 
 local function block_fixes(vm, data, data2, emin, emax, area, minp, maxp, blockseed)