From 1f11af9edb280155483b911dbacf97c7623cb6f7 Mon Sep 17 00:00:00 2001
From: liabru <liambrum@gmail.com>
Date: Wed, 23 Apr 2014 16:40:48 +0100
Subject: [PATCH] added Body.scale

---
 src/body/Body.js         | 28 ++++++++++++++++++++++++++++
 src/geometry/Vertices.js | 27 +++++++++++++++++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/src/body/Body.js b/src/body/Body.js
index 6d9d623..f8846f9 100644
--- a/src/body/Body.js
+++ b/src/body/Body.js
@@ -264,4 +264,32 @@ var Body = {};
         Bounds.update(body.bounds, body.vertices, body.velocity);
     };
 
+    /**
+     * Scales the body, including updating physical properties (mass, area, axes, inertia), from a point (default is centre)
+     * @method translate
+     * @param {body} body
+     * @param {number} scaleX
+     * @param {number} scaleY
+     * @param {vector} point
+     */
+    Body.scale = function(body, scaleX, scaleY, point) {
+        // scale vertices
+        Vertices.scale(body.vertices, scaleX, scaleY, point);
+
+        // update properties
+        body.axes = Axes.fromVertices(body.vertices);
+        body.area = Vertices.area(body.vertices);
+        body.mass = body.density * body.area;
+        body.inverseMass = 1 / body.mass;
+
+        // update inertia (requires vertices to be at origin)
+        Vertices.translate(body.vertices, { x: -body.position.x, y: -body.position.y });
+        body.inertia = Vertices.inertia(body.vertices, body.mass);
+        body.inverseInertia = 1 / body.inertia;
+        Vertices.translate(body.vertices, { x: body.position.x, y: body.position.y });
+
+        // update bounds
+        Bounds.update(body.bounds, body.vertices, body.velocity);
+    };
+
 })();
\ No newline at end of file
diff --git a/src/geometry/Vertices.js b/src/geometry/Vertices.js
index 5afe0cc..ea3a899 100644
--- a/src/geometry/Vertices.js
+++ b/src/geometry/Vertices.js
@@ -167,4 +167,31 @@ var Vertices = {};
         return true;
     };
 
+    /**
+     * Scales the vertices from a point (default is centre)
+     * @method scale
+     * @param {vertices} vertices
+     * @param {number} scaleX
+     * @param {number} scaleY
+     * @param {vector} point
+     */
+     Vertices.scale = function(vertices, scaleX, scaleY, point) {
+        if (scaleX === 1 && scaleY === 1)
+            return vertices;
+
+        point = point || Vertices.centre(vertices);
+
+        var vertex,
+            delta;
+
+        for (var i = 0; i < vertices.length; i++) {
+            vertex = vertices[i];
+            delta = Vector.sub(vertex, point);
+            vertices[i].x = point.x + delta.x * scaleX;
+            vertices[i].y = point.y + delta.y * scaleY;
+        }
+
+        return vertices;
+     };
+
 })();
\ No newline at end of file