Make physics more fun

backend/src/physics/functions/move-circle.ts

@@ -0,0 +1,70 @@
+import { vec2 } from 'gl-matrix';
+import { Circle, GameObject, rotate90Deg } from 'shared';
+import { CirclePhysical } from '../../objects/circle-physical';
+import { reactsToCollision } from '../physicals/reacts-to-collision';
+import { evaluateSdf } from './evaluate-sdf';
+import { Physical } from '../physicals/physical';
+
+export const moveCircle = (
+  circle: CirclePhysical,
+  delta: vec2,
+  possibleIntersectors: Array<Physical>,
+): {
+  realDelta: vec2;
+  hitSurface: boolean;
+  normal?: vec2;
+  tangent?: vec2;
+  hitObject?: GameObject;
+} => {
+  const nextCircle = new Circle(vec2.clone(circle.center), circle.radius);
+  vec2.add(nextCircle.center, nextCircle.center, delta);
+
+  possibleIntersectors = possibleIntersectors.filter(
+    (b) => b.gameObject !== circle.gameObject && b.canCollide,
+  );
+
+  const sdfAtCenter = evaluateSdf(nextCircle.center, possibleIntersectors);
+
+  if (sdfAtCenter > nextCircle.radius) {
+    circle.center = vec2.add(circle.center, circle.center, delta);
+
+    return {
+      realDelta: delta,
+      hitSurface: false,
+    };
+  }
+
+  const intersecting = possibleIntersectors.find(
+    (i) => i.distance(nextCircle.center) <= circle.radius,
+  )!;
+
+  if (reactsToCollision(intersecting)) {
+    intersecting.onCollision(circle.gameObject);
+  }
+
+  if (reactsToCollision(circle)) {
+    circle.onCollision(intersecting.gameObject);
+  }
+
+  const dx =
+    evaluateSdf(vec2.add(vec2.create(), nextCircle.center, vec2.fromValues(0.01, 0)), [
+      intersecting,
+    ]) - sdfAtCenter;
+  const dy =
+    evaluateSdf(vec2.add(vec2.create(), nextCircle.center, vec2.fromValues(0, 0.01)), [
+      intersecting,
+    ]) - sdfAtCenter;
+  const normal = vec2.fromValues(dx, dy);
+  vec2.normalize(normal, normal);
+  const rotatedNormal = rotate90Deg(normal);
+  return {
+    realDelta: delta,
+    hitSurface: true,
+    normal,
+    hitObject: intersecting?.gameObject,
+    tangent:
+      vec2.dot(rotatedNormal, delta) < 0
+        ? vec2.scale(rotatedNormal, rotatedNormal, -1)
+        : rotatedNormal,
+  };
+};