Improve mapgen, add grass, and include the fill tool.

mods/rgt_world/biomes.lua

@@ -0,0 +1,71 @@
+minetest.register_biome {
+    name = "forest",
+
+    node_top = "dirt_grass",
+    depth_top = 1,
+
+    node_filler = "dirt",
+    depth_filler = 5,
+
+    node_riverbed = "dirt",
+    depth_riverbed = 3,
+    
+    node_dungeon = "cobble",
+    node_dungeon_alt = "stone_brick_large",
+
+    
+    y_max = 3000,
+    y_min = 2,
+    vertical_blend = 2,
+
+    heat_point = 50,
+    humidity_point = 50,
+}
+
+minetest.register_biome {
+    name = "plains",
+
+    node_top = "dirt_grass",
+    depth_top = 1,
+
+    node_filler = "dirt",
+    depth_filler = 5,
+
+    node_riverbed = "dirt",
+    depth_riverbed = 3,
+    
+    node_dungeon = "cobble",
+    node_dungeon_alt = "stone_brick_large",
+
+    
+    y_max = 3000,
+    y_min = 2,
+    vertical_blend = 2,
+
+    heat_point = 50,
+    humidity_point = 30,
+}
+
+minetest.register_biome {
+    name = "beach",
+
+    node_top = "sand",
+    depth_top = 1,
+
+    node_filler = "sand",
+    depth_filler = 2,
+
+    node_riverbed = "sand",
+    depth_riverbed = 3,
+    
+    node_dungeon = "cobble",
+    node_dungeon_alt = "stone_brick_large",
+
+    
+    y_max = 1,
+    y_min = -3,
+    vertical_blend = 1,
+
+    heat_point = 50,
+    humidity_point = 50,
+}