From 50a89d0217f951f221801a3ed1a0f79d250402e9 Mon Sep 17 00:00:00 2001
From: liabru <liabru@brm.io>
Date: Sat, 25 Nov 2017 14:16:38 +0000
Subject: [PATCH] fix Body.scale for compound bodies

---
 src/body/Body.js | 44 ++++++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 18 deletions(-)

diff --git a/src/body/Body.js b/src/body/Body.js
index 59a4f3d8..fcb18c1c 100644
--- a/src/body/Body.js
+++ b/src/body/Body.js
@@ -525,35 +525,50 @@ var Axes = require('../geometry/Axes');
      * @param {vector} [point]
      */
     Body.scale = function(body, scaleX, scaleY, point) {
+        var totalArea = 0,
+            totalInertia = 0;
+
         point = point || body.position;
 
         for (var i = 0; i < body.parts.length; i++) {
             var part = body.parts[i];
 
-            // scale position
-            part.position.x = point.x + (part.position.x - point.x) * scaleX;
-            part.position.y = point.y + (part.position.y - point.y) * scaleY;
-
             // scale vertices
             Vertices.scale(part.vertices, scaleX, scaleY, point);
 
             // update properties
             part.axes = Axes.fromVertices(part.vertices);
+            part.area = Vertices.area(part.vertices);
+            Body.setMass(part, body.density * part.area);
 
-            if (!body.isStatic) {
-                part.area = Vertices.area(part.vertices);
-                Body.setMass(part, body.density * part.area);
+            // update inertia (requires vertices to be at origin)
+            Vertices.translate(part.vertices, { x: -part.position.x, y: -part.position.y });
+            Body.setInertia(part, Body._inertiaScale * Vertices.inertia(part.vertices, part.mass));
+            Vertices.translate(part.vertices, { x: part.position.x, y: part.position.y });
 
-                // update inertia (requires vertices to be at origin)
-                Vertices.translate(part.vertices, { x: -part.position.x, y: -part.position.y });
-                Body.setInertia(part, Vertices.inertia(part.vertices, part.mass));
-                Vertices.translate(part.vertices, { x: part.position.x, y: part.position.y });
+            if (i > 0) {
+                totalArea += part.area;
+                totalInertia += part.inertia;
             }
 
+            // scale position
+            part.position.x = point.x + (part.position.x - point.x) * scaleX;
+            part.position.y = point.y + (part.position.y - point.y) * scaleY;
+
             // update bounds
             Bounds.update(part.bounds, part.vertices, body.velocity);
         }
 
+        // handle parent body
+        if (body.parts.length > 1) {
+            body.area = totalArea;
+
+            if (!body.isStatic) {
+                Body.setMass(body, body.density * totalArea);
+                Body.setInertia(body, totalInertia);
+            }
+        }
+
         // handle circles
         if (body.circleRadius) { 
             if (scaleX === scaleY) {
@@ -563,13 +578,6 @@ var Axes = require('../geometry/Axes');
                 body.circleRadius = null;
             }
         }
-
-        if (!body.isStatic) {
-            var total = _totalProperties(body);
-            body.area = total.area;
-            Body.setMass(body, total.mass);
-            Body.setInertia(body, total.inertia);
-        }
     };
 
     /**