almost forgot to commit today

src/main.lua

@@ -67,7 +67,7 @@ love.draw = function()
   for x = 1, map.size do
     for y = 1, map.size do
       -- print(x, y) -- TEMP why am I getting an out of bounds?
-      local value = map.terrain[x][y]
+      local value = map.biome[x][y]
       if value then
         love.graphics.setColor(value)
         love.graphics.rectangle("fill", x * map.tile_size, y * map.tile_size, map.tile_size, map.tile_size)

src/map_nextgen.lua

@@ -1,5 +1,6 @@
 -- NOTE the API of this file should probably change?
 
+local lume = require "lib.lume"
 local simplex = require "lib.simplex"
 
 local simplex_map = {}
@@ -57,28 +58,111 @@ simplex_map.generate = function(size, scale, min, max)
     end
   end
 
+  if min or max then
     min = min or 0
     max = max or 1
     simplex_map.normalize(map, min, max)
+  end
 
   return map
 end
 
+local biomes = {
+  -- biomes are checked in order, with the first candidate always being selected
+  [900] = {
+    name = "deep ocean",
+    altitude = {min = -math.huge, max = -5000},
+    temperature = {min = -math.huge, max = math.huge},
+    rainfall = {min = -math.huge, max = math.huge},
+    color = {0, 0, 0.25, 1},
+  },
+  [1000] = {
+    name = "ocean (definition, 0 meters)",
+    altitude = {min = -math.huge, max = 0},
+    temperature = {min = -math.huge, max = math.huge},
+    rainfall = {min = -math.huge, max = math.huge},
+    color = {0, 0, 0.5, 1},
+  },
+  [2000] = {
+    name = "snowline (middle estimate)",
+    altitude = {min = 4000, max = math.huge},
+    temperature = {min = -math.huge, max = math.huge},
+    rainfall = {min = -math.huge, max = math.huge},
+    color = {1, 1, 1, 1},
+  },
+  [2100] = {
+    name = "alpine zone",
+    altitude = {min = 3500, max = math.huge},
+    temperature = {min = -math.huge, max = math.huge},
+    rainfall = {min = -math.huge, max = math.huge},
+    color = {0.8, 0.8, 0.8, 1},
+  },
+  [2200] = {
+    name = "subalpine zone",
+    altitude = {min = 3000, max = math.huge},
+    temperature = {min = -math.huge, max = math.huge},
+    rainfall = {min = -math.huge, max = math.huge},
+    color = {0.67, 0.67, 0.67, 1},
+  },
+  [2300] = {
+    name = "montane zone",
+    altitude = {min = 2500, max = math.huge},
+    temperature = {min = -math.huge, max = math.huge},
+    rainfall = {min = -math.huge, max = math.huge},
+    color = {0.67, 0.67, 0.5, 1},
+  },
+}
+
 local generate = function()
   local map = {}
   map.size = 500
   map.tile_size = 1 -- TODO tile_size really shouldn't be the responsibility of the map generator - it's a rendering detail, not a map feature
-  map.altitude = {}
+  map.altitude = simplex_map.generate(map.size, 0.005, 0, 1) -- meters
+  map.temperature = simplex_map.generate(map.size, 0.005, -89.2, 56.7) -- celsius
+  map.rainfall = simplex_map.generate(map.size, 0.005, 18, 3240) -- millimeters rainfall
+
+  local function earthlike_altitude_adjustment(altitude)
+    -- TODO replace with a simpler function?
+    return 6099 - 114909 * altitude + 830891 * altitude^2 - 2.72e6 * altitude^3 + 4.19e6 * altitude^4 - 3.02e6 * altitude^5 + 815866 * altitude^6
+  end
 
-  map.terrain = simplex_map.generate(map.size)
   for x = 1, map.size do
     for y = 1, map.size do
-      local value = map.terrain[x][y]
+      map.altitude[x][y] = earthlike_altitude_adjustment(map.altitude[x][y])
-      map.terrain[x][y] = {value, value, value, 1}
     end
   end
+  map.altitude.min = simplex_map.min(map.altitude)
+  map.altitude.max = simplex_map.max(map.altitude)
 
-  -- NOTE this is missing the radius modifier, so it's a square map
+  local biome_order = {}
+  for order in pairs(biomes) do
+    biome_order[#biome_order + 1] = order
+  end
+  table.sort(biome_order)
+
+  local radius_squared = (map.size / 2)^2
+  map.biome = {}
+  for x = 1, map.size do
+    map.biome[x] = {}
+    for y = 1, map.size do
+      if lume.distance(x, y, map.size / 2, map.size / 2, true) < radius_squared then
+        for _, order in ipairs(biome_order) do
+          local biome = biomes[order]
+          local altitude = map.altitude[x][y]
+          if altitude >= biome.altitude.min and altitude <= biome.altitude.max then
+            local temperature = map.temperature[x][y]
+            if temperature >= biome.temperature.min and temperature <= biome.temperature.max then
+              local rainfall = map.rainfall[x][y]
+              if rainfall >= biome.rainfall.min and rainfall <= biome.rainfall.max then
+                map.biome[x][y] = biome.color
+                break
+              end
+            end
+          end
+        end
+      end
+    end
+  end
 
   return map
 end