Simple, lightweight Parallax Engine that reacts to the orientation of a smart device. Where no gyroscope or motion detection hardware is available, the position of the cursor is used instead.

Check out this demo to see it in action!

Simply create a list of elements giving each item that you want to move within your parallax scene a class of layer and a data-depth attribute specifying its depth within the scene. A depth of 0 will cause the layer to remain stationary, and a depth of 1 will cause the layer to move by the total effect of the calculated motion. Values inbetween 0 and 1 will cause the layer to move by an amount relative to the supplied ratio.

<ul id="scene">
  <li class="layer" data-depth="0.00"><img src="layer1.png"></li>
  <li class="layer" data-depth="0.20"><img src="layer2.png"></li>
  <li class="layer" data-depth="0.40"><img src="layer3.png"></li>
  <li class="layer" data-depth="0.60"><img src="layer4.png"></li>
  <li class="layer" data-depth="0.80"><img src="layer5.png"></li>
  <li class="layer" data-depth="1.00"><img src="layer6.png"></li>
</ul>

To kickoff a Parallax scene, simply select your parent DOM Element and pass it to the Parallax constructor.

var scene = document.getElementById('scene');
var parallax = new Parallax(scene);

There are a number of behaviours that you can setup for any given Parallax instance. These behaviours can either be specified in the markup via data attributes or in JavaScript via the constructor and API.

In addition to the behaviours described above, there are two methods enable() and disable() that activate and deactivate the Parallax instance respectively.

<ul id="scene"
  data-calibrate-x="false"
  data-calibrate-y="true"
  data-invert-x="false"
  data-invert-y="true"
  data-limit-x="false"
  data-limit-y="10"
  data-scalar-x="2"
  data-scalar-y="8"
  data-friction-x="0.2"
  data-friction-y="0.8">
  <li class="layer" data-depth="0.00"><img src="graphics/layer1.png"></li>
  <li class="layer" data-depth="0.20"><img src="graphics/layer2.png"></li>
  <li class="layer" data-depth="0.40"><img src="graphics/layer3.png"></li>
  <li class="layer" data-depth="0.60"><img src="graphics/layer4.png"></li>
  <li class="layer" data-depth="0.80"><img src="graphics/layer5.png"></li>
  <li class="layer" data-depth="1.00"><img src="graphics/layer6.png"></li>
</ul>

var scene = document.getElementById('scene');
var parallax = new Parallax(scene, {
  calibrateX: false,
  calibrateY: true,
  invertX: false,
  invertY: true,
  limitX: false,
  limitY: 10,
  scalarX: 2,
  scalarY: 8,
  frictionX: 0.2,
  frictionY: 0.8
});

var scene = document.getElementById('scene');
var parallax = new Parallax(scene);
parallax.enable();
parallax.disable();
parallax.calibrate(false, true);
parallax.invert(false, true);
parallax.limit(false, 10);
parallax.scalar(2, 8);
parallax.friction(0.2, 0.8);

If you're using jQuery or Zepto and would prefer to use Parallax.js as a plugin, you're in luck!

$('#scene').parallax();

$('#scene').parallax({
  calibrateX: false,
  calibrateY: true,
  invertX: false,
  invertY: true,
  limitX: false,
  limitY: 10,
  scalarX: 2,
  scalarY: 8,
  frictionX: 0.2,
  frictionY: 0.8
});

var $scene = $('#scene').parallax();
$scene.parallax('enable');
$scene.parallax('disable');
$scene.parallax('calibrate', false, true);
$scene.parallax('invert', false, true);
$scene.parallax('limit', false, 10);
$scene.parallax('scalar', 2, 8);
$scene.parallax('friction', 0.2, 0.8);

If you are writing a native iOS application and would like to use parallax.js within a UIWebView, you will need to do a little bit of work to get it running.

UIWebView no longer automatically receives the deviceorientation event, so your native application must intercept the events from the gyroscope and reroute them to the UIWebView:

1. Include the CoreMotion framework #import <CoreMotion/CoreMotion.h> and create a reference to the UIWebView @property(nonatomic, strong) IBOutlet UIWebView *parallaxWebView;
2. Add a property to the app delegate (or controller that will own the UIWebView) @property(nonatomic, strong) CMMotionManager *motionManager;
3. Finally, make the following calls:

  self.motionManager = [[CMMotionManager alloc] init];

  if (self.motionManager.isGyroAvailable && !self.motionManager.isGyroActive) {

    [self.motionManager setGyroUpdateInterval:0.5f]; // Set the event update frequency (in seconds)

    [self.motionManager startGyroUpdatesToQueue:NSOperationQueue.mainQueue
                                    withHandler:^(CMGyroData *gyroData, NSError *error) {

      NSString *js = [NSString stringWithFormat:@"parallax.onDeviceOrientation({beta:%f, gamma:%f})", gyroData.rotationRate.x, gyroData.rotationRate.y];

      [self.parallaxWebView stringByEvaluatingJavaScriptFromString:js];

    }];
  }

cd build
npm install
node build.js

Matthew Wagerfield: @mwagerfield

Licensed under MIT. Enjoy.