From 55d69e16b6fde41a2c5fc0625fff3f436bfce88e Mon Sep 17 00:00:00 2001
From: Cameron Foale <cameron@cocoademon.com.au>
Date: Wed, 18 Dec 2013 11:57:55 +1100
Subject: [PATCH] Add an example to show framerate independence in physics
 calculations

---
 examples/_site/examples.json               |   4 +
 examples/physics/framerate independence.js | 137 +++++++++++++++++++++
 2 files changed, 141 insertions(+)
 create mode 100644 examples/physics/framerate independence.js

diff --git a/examples/_site/examples.json b/examples/_site/examples.json
index bb3cc821..4d46fb26 100644
--- a/examples/_site/examples.json
+++ b/examples/_site/examples.json
@@ -534,6 +534,10 @@
       "file": "bounce.js",
       "title": "bounce"
     },
+    {
+      "file": "framerate+independence.js",
+      "title": "framerate independence"
+    },
     {
       "file": "mass+velocity+test.js",
       "title": "mass velocity test"
diff --git a/examples/physics/framerate independence.js b/examples/physics/framerate independence.js
new file mode 100644
index 00000000..94e7814e
--- /dev/null
+++ b/examples/physics/framerate independence.js	
@@ -0,0 +1,137 @@
+var game = new Phaser.Game(800, 600, Phaser.CANVAS, 'phaser-example', { preload: preload, create: create, update: update, render: render });
+
+// This example pokes around with the internal Phaser time and physics systems
+// just to demonstrate collision and physics behaviour with different framerates.
+// Doing this in your game is not recommended
+
+function preload() {
+
+    game.load.image('sprite', 'assets/sprites/diamond.png');
+
+}
+
+var sprite, box;
+
+var configurations = [
+    {
+        framerate: null,
+        description: 'Default (as fast as possible)',
+        color: 0x999999
+    },
+    {
+        framerate: 120,
+        color: 0x0000FF
+    },
+    {
+        framerate: 60,
+        color: 0x00FF00
+    },
+    {
+        framerate: 30,
+        color: 0x00CCCC
+    },
+    {
+        framerate: 11,
+        color: 0xFF0000
+    },
+    {
+        framerate: 7,
+        color: 0xCC00CC
+    },
+    {
+        framerate: 5,
+        color: 0xCCCC00
+    },
+    {
+        framerate: function() { return Math.random() * 30 + 30; },
+        description: 'Jittered 30-60hz',
+        color: 0x333399
+    },
+    {
+        framerate: function() { return Math.random() * 119 + 1; },
+        description: 'Jittered 1-120hz',
+        color: 0x339933
+    }
+
+];
+
+var configurationIndex = 0;
+var currentConfiguration = configurations[0];
+
+var floor = game.height - 40;
+
+// Here we keep a copy of the original framerate update method
+Phaser.Time.prototype.originalUpdate = Phaser.Time.prototype.update;
+
+// And replace it with one that overrides the framerate
+Phaser.Time.prototype.update = function (time) {
+
+    this.originalUpdate(time);
+
+    if(currentConfiguration.framerate)
+    {
+        if(typeof(currentConfiguration.framerate) == 'function')
+        {
+            this.physicsElapsed = 1.0 / currentConfiguration.framerate();
+        } else {
+            this.physicsElapsed = 1.0 / currentConfiguration.framerate;
+        }
+    }
+};
+
+function resetSprite()
+{
+    sprite.body.x = 40;
+    sprite.body.y = floor;
+    sprite.body.velocity.x = 300;
+    sprite.body.velocity.y = -900;
+    sprite.body.gravity.y = 20;
+    
+};
+
+function create() {
+
+    sprite = game.add.sprite(40, floor, 'sprite');
+    sprite.body.bounce.y = 0.5;
+    resetSprite();
+
+    for(var i = 0; i < configurations.length; i++)
+    {
+        configurations[i].graphics = game.add.graphics(0, 0);
+        configurations[i].points = [];
+    }
+
+    box = game.add.sprite(450, floor - 40, 'missing');
+    box.width = 100;
+    box.body.immovable = true;
+};
+
+function update() {
+
+    game.physics.collide(sprite, box);
+
+    currentConfiguration.points.push([sprite.center.x, sprite.center.y]);
+
+    if(sprite.body.velocity.y > 0 && sprite.body.y > floor)
+    {
+        currentConfiguration.graphics.clear();
+        currentConfiguration.graphics.lineStyle(1, currentConfiguration.color, 1)
+        currentConfiguration.graphics.moveTo(currentConfiguration.points[0][0], currentConfiguration.points[0][1]);
+
+        for(var i = 1; i < currentConfiguration.points.length; i++)
+        {
+            currentConfiguration.graphics.lineTo(currentConfiguration.points[i][0], currentConfiguration.points[i][1]);          
+        }
+
+        currentConfiguration.points.length = 0;
+
+        configurationIndex = (configurationIndex + 1) % configurations.length;
+        currentConfiguration = configurations[configurationIndex];
+
+        resetSprite();
+    }
+};
+
+function render() {
+    game.debug.renderText("Framerate: " + (currentConfiguration.description || (currentConfiguration.framerate + 'hz')), 10, 40);
+};
\ No newline at end of file