Implement missing map tiles, add a new meadow biome, make biomes more granular.

mapgen.lua

@@ -4,20 +4,25 @@ function init_mapgen()
    uid_seed = 2229 -- arbitrarily chosen number
 
    -- Metadata for different biomes
-   -- frequencies don't have to add up to 100, but they should by convention
    -- tile_frequencies tuples are {frequency, sprite_index}, see index_map.md
+   -- frequencies by convention add up to 1000, but this is arbitrary, the
+   -- only concern is the space consumed by the resulting tables.
    biome_data = {
+      meadow = {
+         biome_frequency = 20,
+         tile_frequencies = { {525, 2}, {200, 5}, {200, 6}, {55, 18}, {19, 3}, {1, 4} }
+      },
       grassland = {
-         biome_frequency = 75,
-         tile_frequencies = { {40, 2}, {28, 5}, {28, 6}, {3, 3}, {1, 4} }
+         biome_frequency = 55,
+         tile_frequencies = { {500, 2}, {345, 18}, {4, 3}, {1, 4}, {100, 5}, {50, 6} }
       },
       forest = {
          biome_frequency = 20,
-         tile_frequencies = { {60, 2}, {20, 4}, {5, 3}, {5, 5}, {4, 7}, {5, 6}, {1, 8} }
+         tile_frequencies = { {600, 2}, {200, 4}, {50, 3}, {50, 5}, {40, 7}, {59, 6}, {1, 8} }
       },
       desert = {
          biome_frequency = 5,
-         tile_frequencies = { {80, 9}, {10, 11}, {6, 13}, {3, 12}, {1, 10} },
+         tile_frequencies = { {800, 9}, {109, 11}, {60, 13}, {30, 12}, {1, 10} },
       }
    }
 
@@ -25,7 +30,7 @@ function init_mapgen()
    -- Lua's pairs() function appears not to guarantee a consistent return order,
    -- and we want our world to be deterministically generated,
    -- so the biome_metadata array needs to have its entries appear consistently.
-   biome_list = {"grassland", "forest", "desert"}
+   biome_list = {"grassland", "meadow", "forest", "desert"}
 
    -- this is the frequency list for the biomes themselves
    biome_metadata = {}