Default/mapgen: Re-add grassy sand dune biomes

mods/default/mapgen.lua

@@ -446,12 +446,30 @@ function default.register_biomes()
 		--depth_water_top = ,
 		--node_water = "",
 		--node_river_water = "",
-		y_min = 5,
+		y_min = 6,
 		y_max = 31000,
 		heat_point = 40,
 		humidity_point = 35,
 	})
 
+	minetest.register_biome({
+		name = "stone_grassland_dunes",
+		--node_dust = "",
+		node_top = "default:sand",
+		depth_top = 1,
+		node_filler = "default:sand",
+		depth_filler = 2,
+		--node_stone = "",
+		--node_water_top = "",
+		--depth_water_top = ,
+		--node_water = "",
+		--node_river_water = "",
+		y_min = 5,
+		y_max = 5,
+		heat_point = 40,
+		humidity_point = 35,
+	})
+
 	minetest.register_biome({
 		name = "stone_grassland_ocean",
 		--node_dust = "",
@@ -483,12 +501,30 @@ function default.register_biomes()
 		--depth_water_top = ,
 		--node_water = "",
 		--node_river_water = "",
-		y_min = 5,
+		y_min = 6,
 		y_max = 31000,
 		heat_point = 40,
 		humidity_point = 65,
 	})
 
+	minetest.register_biome({
+		name = "coniferous_forest_dunes",
+		--node_dust = "",
+		node_top = "default:sand",
+		depth_top = 1,
+		node_filler = "default:sand",
+		depth_filler = 3,
+		--node_stone = "",
+		--node_water_top = "",
+		--depth_water_top = ,
+		--node_water = "",
+		--node_river_water = "",
+		y_min = 5,
+		y_max = 5,
+		heat_point = 40,
+		humidity_point = 65,
+	})
+
 	minetest.register_biome({
 		name = "coniferous_forest_ocean",
 		--node_dust = "",
@@ -520,12 +556,30 @@ function default.register_biomes()
 		--depth_water_top = ,
 		--node_water = "",
 		--node_river_water = "",
-		y_min = 5,
+		y_min = 6,
 		y_max = 31000,
 		heat_point = 60,
 		humidity_point = 35,
 	})
 
+	minetest.register_biome({
+		name = "sandstone_grassland_dunes",
+		--node_dust = "",
+		node_top = "default:sand",
+		depth_top = 1,
+		node_filler = "default:sand",
+		depth_filler = 2,
+		node_stone = "default:sandstone",
+		--node_water_top = "",
+		--depth_water_top = ,
+		--node_water = "",
+		--node_river_water = "",
+		y_min = 5,
+		y_max = 5,
+		heat_point = 60,
+		humidity_point = 35,
+	})
+
 	minetest.register_biome({
 		name = "sandstone_grassland_ocean",
 		--node_dust = "",
@@ -879,7 +933,9 @@ local function register_grass_decoration(offset, scale, length)
 			persist = 0.6
 		},
 		biomes = {"stone_grassland", "sandstone_grassland",
-			"deciduous_forest", "coniferous_forest"},
+			"deciduous_forest", "coniferous_forest",
+			"stone_grassland_dunes", "sandstone_grassland_dunes",
+			"coniferous_forest_dunes"},
 		y_min = 1,
 		y_max = 31000,
 		decoration = "default:grass_"..length,