refactor: grid generation

src/modules/temperature.ts

@@ -0,0 +1,47 @@
+import * as d3 from "d3";
+
+import {TIME} from "config/logging";
+import {minmax} from "utils/numberUtils";
+import {getInputNumber} from "utils/nodeUtils";
+import {MIN_LAND_HEIGHT} from "config/generation";
+
+const interpolate = d3.easePolyInOut.exponent(0.5); // interpolation function
+
+export function calculateTemperatures(grid: IGridWithHeights) {
+  TIME && console.time("calculateTemperatures");
+
+  const {cells, cellsX, points} = grid;
+  const heights = cells.h;
+
+  const temperatures = new Int8Array(heights.length); // temperature array
+
+  // temperature decreases by 6.5 Celsius per kilometer
+  const heightExponent = getInputNumber("heightExponentInput");
+  function decreaseTempFromElevation(height: number) {
+    if (height < MIN_LAND_HEIGHT) return 0;
+
+    const realHeight = Math.pow(height - 18, heightExponent);
+    return (realHeight / 1000) * 6.5;
+  }
+
+  const tEq = getInputNumber("temperatureEquatorInput");
+  const tPole = getInputNumber("temperaturePoleInput");
+  const tDelta = tEq - tPole;
+
+  const {latN, latT} = window.mapCoordinates;
+
+  d3.range(0, heights.length, cellsX).forEach(rowStart => {
+    const y = points[rowStart][1];
+    const lat = Math.abs(latN - (y / graphHeight) * latT); // [0; 90]
+
+    const initTemp = tEq - interpolate(lat / 90) * tDelta;
+    for (let i = rowStart; i < rowStart + cellsX; i++) {
+      const elevationDecrease = decreaseTempFromElevation(heights[i]);
+      temperatures[i] = minmax(initTemp - elevationDecrease, -128, 127);
+    }
+  });
+
+  TIME && console.timeEnd("calculateTemperatures");
+
+  return temperatures;
+}