feat: move biomes code to a separate module, reduce deserts amount

modules/biomes.js

@@ -0,0 +1,144 @@
+"use strict";
+
+const MIN_LAND_HEIGHT = 20;
+
+const names = [
+  "Marine",
+  "Hot desert",
+  "Cold desert",
+  "Savanna",
+  "Grassland",
+  "Tropical seasonal forest",
+  "Temperate deciduous forest",
+  "Tropical rainforest",
+  "Temperate rainforest",
+  "Taiga",
+  "Tundra",
+  "Glacier",
+  "Wetland"
+];
+
+window.Biomes = (function () {
+  const getDefault = () => {
+    const name = [
+      "Marine",
+      "Hot desert",
+      "Cold desert",
+      "Savanna",
+      "Grassland",
+      "Tropical seasonal forest",
+      "Temperate deciduous forest",
+      "Tropical rainforest",
+      "Temperate rainforest",
+      "Taiga",
+      "Tundra",
+      "Glacier",
+      "Wetland"
+    ];
+
+    const color = [
+      "#466eab",
+      "#fbe79f",
+      "#b5b887",
+      "#d2d082",
+      "#c8d68f",
+      "#b6d95d",
+      "#29bc56",
+      "#7dcb35",
+      "#409c43",
+      "#4b6b32",
+      "#96784b",
+      "#d5e7eb",
+      "#0b9131"
+    ];
+    const habitability = [0, 4, 10, 22, 30, 50, 100, 80, 90, 12, 4, 0, 12];
+    const iconsDensity = [0, 3, 2, 120, 120, 120, 120, 150, 150, 100, 5, 0, 150];
+    const icons = [
+      {},
+      {dune: 3, cactus: 6, deadTree: 1},
+      {dune: 9, deadTree: 1},
+      {acacia: 1, grass: 9},
+      {grass: 1},
+      {acacia: 8, palm: 1},
+      {deciduous: 1},
+      {acacia: 5, palm: 3, deciduous: 1, swamp: 1},
+      {deciduous: 6, swamp: 1},
+      {conifer: 1},
+      {grass: 1},
+      {},
+      {swamp: 1}
+    ];
+    const cost = [10, 200, 150, 60, 50, 70, 70, 80, 90, 200, 1000, 5000, 150]; // biome movement cost
+    const biomesMartix = [
+      // hot ↔ cold [>19°C; <-4°C]; dry ↕ wet
+      new Uint8Array([1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 10]),
+      new Uint8Array([3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 9, 9, 9, 9, 10, 10, 10]),
+      new Uint8Array([5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 9, 9, 9, 9, 9, 10, 10, 10]),
+      new Uint8Array([5, 6, 6, 6, 6, 6, 6, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10]),
+      new Uint8Array([7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 10, 10])
+    ];
+
+    // parse icons weighted array into a simple array
+    for (let i = 0; i < icons.length; i++) {
+      const parsed = [];
+      for (const icon in icons[i]) {
+        for (let j = 0; j < icons[i][icon]; j++) {
+          parsed.push(icon);
+        }
+      }
+      icons[i] = parsed;
+    }
+
+    return {i: d3.range(0, name.length), name, color, biomesMartix, habitability, iconsDensity, icons, cost};
+  };
+
+  // assign biome id for each cell
+  function define() {
+    TIME && console.time("defineBiomes");
+
+    const {fl: flux, r: riverIds, h: heights, c: neighbors, g: gridReference} = pack.cells;
+    const {temp, prec} = grid.cells;
+    pack.cells.biome = new Uint8Array(pack.cells.i.length); // biomes array
+
+    for (let cellId = 0; cellId < heights.length; cellId++) {
+      const height = heights[cellId];
+      const moisture = height < MIN_LAND_HEIGHT ? 0 : calculateMoisture(cellId);
+      const temperature = temp[gridReference[cellId]];
+      pack.cells.biome[cellId] = getId(moisture, temperature, height, Boolean(riverIds[cellId]));
+    }
+
+    function calculateMoisture(cellId) {
+      let moisture = prec[gridReference[cellId]];
+      if (riverIds[cellId]) moisture += Math.max(flux[cellId] / 10, 2);
+
+      const moistAround = neighbors[cellId]
+        .filter(neibCellId => heights[neibCellId] >= MIN_LAND_HEIGHT)
+        .map(c => prec[gridReference[c]])
+        .concat([moisture]);
+      return rn(4 + d3.mean(moistAround));
+    }
+
+    TIME && console.timeEnd("defineBiomes");
+  }
+
+  function getId(moisture, temperature, height, hasRiver) {
+    if (height < 20) return 0; // all water cells: marine biome
+    if (temperature < -5) return 11; // too cold: permafrost biome
+    if (temperature >= 25 && !hasRiver && moisture < 8) return 1; // too hot and dry: hot desert biome
+    if (isWetland(moisture, temperature, height)) return 12; // too wet: wetland biome
+
+    // in other cases use biome matrix
+    const moistureBand = Math.min((moisture / 5) | 0, 4); // [0-4]
+    const temperatureBand = Math.min(Math.max(20 - temperature, 0), 25); // [0-25]
+    return biomesData.biomesMartix[moistureBand][temperatureBand];
+  }
+
+  function isWetland(moisture, temperature, height) {
+    if (temperature <= -2) return false; // too cold
+    if (moisture > 40 && height < 25) return true; // near coast
+    if (moisture > 24 && height > 24 && height < 60) return true; // off coast
+    return false;
+  }
+
+  return {getDefault, define, getId};
+})();