change gravity scale to variable rather than a constant

liabru · Dec 29, 2015 · a38b227 · a38b227
1 parent 5ff2182
commit a38b227
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Showing 2 changed files with 51 additions and 8 deletions.
diff --git a/src/body/World.js b/src/body/World.js
@@ -34,7 +34,11 @@ var Common = require('../core/Common');
 
         var defaults = {
             label: 'World',
-            gravity: { x: 0, y: 1 },
+            gravity: {
+                x: 0,
+                y: 1,
+                scale: 0.001
+            },
             bounds: { 
                 min: { x: -Infinity, y: -Infinity }, 
                 max: { x: Infinity, y: Infinity } 
@@ -44,34 +48,71 @@ var Common = require('../core/Common');
         return Common.extend(composite, defaults, options);
     };
 
+    /*
+    *
+    *  Properties Documentation
+    *
+    */
+
+    /**
+     * The gravity to apply on the world.
+     *
+     * @property gravity
+     * @type object
+     */
+
+    /**
+     * The gravity x component.
+     *
+     * @property gravity.x
+     * @type object
+     * @default 0
+     */
+
+    /**
+     * The gravity y component.
+     *
+     * @property gravity.y
+     * @type object
+     * @default 1
+     */
+
+    /**
+     * The gravity scale factor.
+     *
+     * @property gravity.scale
+     * @type object
+     * @default 0.001
+     */
+
     // World is a Composite body
     // see src/module/Outro.js for these aliases:
 
     /**
-     * An alias for Composite.clear since World is also a Composite
+     * An alias for Composite.clear
      * @method clear
      * @param {world} world
      * @param {boolean} keepStatic
      */
 
     /**
-     * An alias for Composite.add since World is also a Composite
+     * An alias for Composite.add
      * @method addComposite
      * @param {world} world
      * @param {composite} composite
      * @return {world} The original world with the objects from composite added
      */
 
      /**
-      * An alias for Composite.addBody since World is also a Composite
+      * An alias for Composite.addBody
       * @method addBody
       * @param {world} world
       * @param {body} body
       * @return {world} The original world with the body added
       */
 
      /**
-      * An alias for Composite.addConstraint since World is also a Composite
+      * An alias for Composite.addConstraint
       * @method addConstraint
       * @param {world} world
       * @param {constraint} constraint

diff --git a/src/core/Engine.js b/src/core/Engine.js
@@ -280,7 +280,9 @@ var Body = require('../body/Body');
      * @param {vector} gravity
      */
     var _bodiesApplyGravity = function(bodies, gravity) {
-        if (gravity.x === 0 && gravity.y === 0) {
+        var gravityScale = typeof gravity.scale !== 'undefined' ? gravity.scale : 0.001;
+
+        if ((gravity.x === 0 && gravity.y === 0) || gravityScale === 0) {
             return;
         }
 
@@ -291,8 +293,8 @@ var Body = require('../body/Body');
                 continue;
 
             // apply gravity
-            body.force.y += body.mass * gravity.y * 0.001;
-            body.force.x += body.mass * gravity.x * 0.001;
+            body.force.y += body.mass * gravity.y * gravityScale;
+            body.force.x += body.mass * gravity.x * gravityScale;
         }
     };