fix: SAT divide by 0 NaN fix preserving a_in_b and b_in_a

docs/modules_Circle.js.html

@@ -140,10 +140,8 @@ <h1 class="page-title">
   }
 
   get scale() {
-    return {
-      x: this.scale_x,
-      y: this.scale_y,
-    };
+    // for compatibility in SAT
+    return (this.scale_x + this.scale_y) / 2;
   }
 }
 

docs/modules_SAT.js.html

@@ -100,8 +100,8 @@ <h1 class="page-title">
  * @returns {Boolean}
  */
 function SAT(a, b, result = null, aabb = true) {
-  const a_polygon = a._polygon;
-  const b_polygon = b._polygon;
+  const a_polygon = a._polygon &amp;&amp; !a.radius;
+  const b_polygon = b._polygon &amp;&amp; !b.radius;
 
   let collision = false;
 
@@ -420,8 +420,8 @@ <h1 class="page-title">
     result.a_in_b = a_radius &lt;= b_radius &amp;&amp; length &lt;= b_radius - a_radius;
     result.b_in_a = b_radius &lt;= a_radius &amp;&amp; length &lt;= a_radius - b_radius;
     result.overlap = radius_sum - length;
-    result.overlap_x = difference_x / length;
-    result.overlap_y = difference_y / length;
+    result.overlap_x = length ? difference_x / length : 1;
+    result.overlap_y = length ? difference_y / length : 1;
   }
 
   return true;

package.json

@@ -1,7 +1,7 @@
 {
   "name": "detect-collisions",
   "types": "collisions.d.ts",
-  "version": "2.5.6",
+  "version": "2.6.0",
   "description": "zero-dependency 2d collision detection for circles, polygons, and points (with SAT and BVH)",
   "main": "source/index.js",
   "scripts": {
@@ -11,7 +11,7 @@
     "docs": "yarn docs:make && yarn docs:copy",
     "docs:dev": "yarn docs && node node_modules/@jacekpietal/bouncer.js/bin docs",
     "lint": "eslint ./source --fix",
-    "demo": "yarn build-demo && http-server docs/demo",
+    "demo": "yarn build-demo && bouncer.js docs/demo",
     "build-demo": "webpack && cp -r demo/ docs/",
     "compile": "babel ./source --presets es2015 --out-dir ./es2015",
     "build": "rm -rf ./docs/* && esdoc && webpack",

source/index.spec.js

@@ -1,4 +1,4 @@
-const { Collisions } = require(".");
+const { Collisions, Result, SAT } = require(".");
 
 describe("GIVEN a world with a polygon", () => {
   it("THEN collides with a circle", () => {
@@ -27,4 +27,33 @@ describe("GIVEN a world with a polygon", () => {
 
     expect(world.potentials(rect).length).toBe(2);
   });
+
+  it("THEN collides with two circles at same place", () => {
+    const world = new Collisions();
+    const c1 = world.createCircle(0, 0, 50);
+    const c2 = world.createCircle(0, 0, 100);
+    const result = new Result();
+
+    [c1, c2].forEach((body) => {
+      new SAT(body, body === c1 ? c2 : c1, result);
+
+      expect(result.a_in_b).toBe(body === c1);
+      expect(result.b_in_a).toBe(body === c2);
+      expect(result.overlap).toBe(150);
+    });
+
+    [c1, c2].forEach((body) => {
+      new SAT(body, body === c1 ? c2 : c1, result);
+
+      body.x -= result.overlap * result.overlap_x;
+      body.y -= result.overlap * result.overlap_y;
+    });
+
+    world.update();
+
+    new SAT(c1, c2, result);
+
+    expect(c1.x).toBe(-150);
+    expect(c2.x).toBe(0);
+  });
 });

source/modules/Circle.js

@@ -48,10 +48,8 @@ class Circle extends Polygon {
   }
 
   get scale() {
-    return {
-      x: this.scale_x,
-      y: this.scale_y,
-    };
+    // for compatibility in SAT
+    return (this.scale_x + this.scale_y) / 2;
   }
 }
 

source/modules/SAT.js

@@ -8,8 +8,8 @@
  * @returns {Boolean}
  */
 function SAT(a, b, result = null, aabb = true) {
-  const a_polygon = a._polygon;
-  const b_polygon = b._polygon;
+  const a_polygon = a._polygon && !a.radius;
+  const b_polygon = b._polygon && !b.radius;
 
   let collision = false;
 
@@ -328,8 +328,8 @@ function circleCircle(a, b, result = null) {
     result.a_in_b = a_radius <= b_radius && length <= b_radius - a_radius;
     result.b_in_a = b_radius <= a_radius && length <= a_radius - b_radius;
     result.overlap = radius_sum - length;
-    result.overlap_x = difference_x / length;
-    result.overlap_y = difference_y / length;
+    result.overlap_x = length ? difference_x / length : 1;
+    result.overlap_y = length ? difference_y / length : 1;
   }
 
   return true;