Biomes: Add vertical biome blends (#2120)

Alter a few biome y-limits for consistency.

mods/default/mapgen.lua

@@ -953,7 +953,7 @@ function default.register_biomes(upper_limit)
 		node_riverbed = "default:gravel",
 		depth_riverbed = 2,
 		y_max = upper_limit,
-		y_min = 49,
+		y_min = 47,
 		heat_point = 0,
 		humidity_point = 40,
 	})
@@ -966,7 +966,8 @@ function default.register_biomes(upper_limit)
 		depth_filler = 1,
 		node_riverbed = "default:gravel",
 		depth_riverbed = 2,
-		y_max = 48,
+		vertical_blend = 4,
+		y_max = 46,
 		y_min = 2,
 		heat_point = 0,
 		humidity_point = 40,
@@ -980,6 +981,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 2,
 		node_riverbed = "default:gravel",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = 1,
 		y_min = -3,
 		heat_point = 0,
@@ -994,6 +996,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:gravel",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = -4,
 		y_min = -112,
 		heat_point = 0,
@@ -1012,7 +1015,7 @@ function default.register_biomes(upper_limit)
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
 		y_max = upper_limit,
-		y_min = 2,
+		y_min = 4,
 		heat_point = 25,
 		humidity_point = 70,
 	})
@@ -1025,7 +1028,8 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
-		y_max = 1,
+		vertical_blend = 1,
+		y_max = 3,
 		y_min = -112,
 		heat_point = 25,
 		humidity_point = 70,
@@ -1043,7 +1047,7 @@ function default.register_biomes(upper_limit)
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
 		y_max = upper_limit,
-		y_min = 5,
+		y_min = 4,
 		heat_point = 20,
 		humidity_point = 35,
 	})
@@ -1056,7 +1060,8 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
-		y_max = 4,
+		vertical_blend = 1,
+		y_max = 3,
 		y_min = -112,
 		heat_point = 20,
 		humidity_point = 35,
@@ -1086,6 +1091,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 2,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = 5,
 		y_min = 4,
 		heat_point = 50,
@@ -1130,6 +1136,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = 5,
 		y_min = 4,
 		heat_point = 45,
@@ -1188,6 +1195,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = -2,
 		y_min = -112,
 		heat_point = 60,
@@ -1206,7 +1214,7 @@ function default.register_biomes(upper_limit)
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
 		y_max = upper_limit,
-		y_min = 5,
+		y_min = 4,
 		heat_point = 92,
 		humidity_point = 16,
 	})
@@ -1220,7 +1228,8 @@ function default.register_biomes(upper_limit)
 		node_stone = "default:desert_stone",
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
-		y_max = 4,
+		vertical_blend = 1,
+		y_max = 3,
 		y_min = -112,
 		heat_point = 92,
 		humidity_point = 16,
@@ -1238,7 +1247,7 @@ function default.register_biomes(upper_limit)
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
 		y_max = upper_limit,
-		y_min = 5,
+		y_min = 4,
 		heat_point = 60,
 		humidity_point = 0,
 	})
@@ -1252,7 +1261,7 @@ function default.register_biomes(upper_limit)
 		node_stone = "default:sandstone",
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
-		y_max = 4,
+		y_max = 3,
 		y_min = -112,
 		heat_point = 60,
 		humidity_point = 0,
@@ -1269,7 +1278,7 @@ function default.register_biomes(upper_limit)
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
 		y_max = upper_limit,
-		y_min = 5,
+		y_min = 4,
 		heat_point = 40,
 		humidity_point = 0,
 	})
@@ -1282,7 +1291,8 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
-		y_max = 4,
+		vertical_blend = 1,
+		y_max = 3,
 		y_min = -112,
 		heat_point = 40,
 		humidity_point = 0,
@@ -1326,6 +1336,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = -2,
 		y_min = -112,
 		heat_point = 89,
@@ -1370,6 +1381,7 @@ function default.register_biomes(upper_limit)
 		depth_filler = 3,
 		node_riverbed = "default:sand",
 		depth_riverbed = 2,
+		vertical_blend = 1,
 		y_max = -2,
 		y_min = -112,
 		heat_point = 86,
@@ -1719,7 +1731,7 @@ function default.register_decorations()
 		},
 		biomes = {"taiga", "coniferous_forest", "floatland_coniferous_forest"},
 		y_max = 31000,
-		y_min = 2,
+		y_min = 4,
 		schematic = minetest.get_modpath("default") .. "/schematics/pine_tree.mts",
 		flags = "place_center_x, place_center_z",
 	})
@@ -1739,7 +1751,7 @@ function default.register_decorations()
 		},
 		biomes = {"taiga", "coniferous_forest", "floatland_coniferous_forest"},
 		y_max = 31000,
-		y_min = 2,
+		y_min = 4,
 		schematic = minetest.get_modpath("default") .. "/schematics/small_pine_tree.mts",
 		flags = "place_center_x, place_center_z",
 	})
@@ -1752,7 +1764,7 @@ function default.register_decorations()
 		fill_ratio = 0.0018,
 		biomes = {"taiga", "coniferous_forest", "floatland_coniferous_forest"},
 		y_max = 31000,
-		y_min = 1,
+		y_min = 4,
 		schematic = minetest.get_modpath("default") .. "/schematics/pine_log.mts",
 		flags = "place_center_x",
 		rotation = "random",
@@ -1862,7 +1874,7 @@ function default.register_decorations()
 		},
 		biomes = {"desert"},
 		y_max = 31000,
-		y_min = 5,
+		y_min = 4,
 		schematic = minetest.get_modpath("default") .. "/schematics/large_cactus.mts",
 		flags = "place_center_x",
 		rotation = "random",
@@ -1885,7 +1897,7 @@ function default.register_decorations()
 		},
 		biomes = {"desert"},
 		y_max = 31000,
-		y_min = 5,
+		y_min = 4,
 		decoration = "default:cactus",
 		height = 2,
 		height_max = 5,
@@ -2033,7 +2045,7 @@ function default.register_decorations()
 			flags = "absvalue"
 		},
 		biomes = {"coniferous_forest_dunes", "grassland_dunes"},
-		y_max = 5,
+		y_max = 6,
 		y_min = 4,
 		decoration = {
 			"default:marram_grass_1",
@@ -2057,7 +2069,7 @@ function default.register_decorations()
 			persist = 1.0
 		},
 		biomes = {"tundra"},
-		y_max = 48,
+		y_max = 50,
 		y_min = 2,
 		decoration = "default:permafrost_with_moss",
 		place_offset_y = -1,
@@ -2083,7 +2095,7 @@ function default.register_decorations()
 			persist = 1.0
 		},
 		biomes = {"tundra"},
-		y_max = 48,
+		y_max = 50,
 		y_min = 2,
 		decoration = "default:snow",
 	})