feat(world): add fade constants and scaling logic

src/lib/world.ts

@@ -0,0 +1,45 @@
+const WORLD_FADE_SIZE_DEFAULT = [1.0, 4.0, 15.0, 100.0, 100000.0];
+
+const WORLD_FADE_DIST_DEFAULT = [30.0, 100.0, 200.0, 750.0, 1250.0];
+
+const WORLD_FADE_RANGE_DEFAULT = [5.0, 10.0, 15.0, 20.0, 50.0];
+
+const WORLD_FADE_SIZE = [1.0, 4.0, 15.0, 100.0, 100000.0];
+
+const WORLD_FADE_DIST_MIN = [25.0, 90.0, 185.0, 730.0, 1200.0];
+
+const WORLD_FADE_DIST_MAX = [30.0, 100.0, 200.0, 750.0, 1250.0];
+
+const getSizeCategory = (size: number) => {
+  let f: number;
+  for (f = 0; f < WORLD_FADE_SIZE.length; f++) {
+    if (size <= WORLD_FADE_SIZE[f]) {
+      break;
+    }
+  }
+
+  return f;
+};
+
+const scaleFadeDist = (scale: number) => {
+  for (let i = 0; i < WORLD_FADE_SIZE_DEFAULT.length; i++) {
+    const first = i === 0;
+    const last = i === WORLD_FADE_SIZE_DEFAULT.length - 1;
+    const s = first || last ? 1.0 : scale;
+
+    WORLD_FADE_SIZE[i] = WORLD_FADE_SIZE_DEFAULT[i];
+    WORLD_FADE_DIST_MAX[i] = WORLD_FADE_DIST_DEFAULT[i] * s;
+    WORLD_FADE_DIST_MIN[i] = WORLD_FADE_DIST_MAX[i] - WORLD_FADE_RANGE_DEFAULT[i];
+  }
+};
+
+// TODO modify scale based on config
+scaleFadeDist(1.5);
+
+export {
+  getSizeCategory,
+  scaleFadeDist,
+  WORLD_FADE_SIZE,
+  WORLD_FADE_DIST_MIN,
+  WORLD_FADE_DIST_MAX,
+};