Levitate - LeapMotion Frame Processing

Motivation

The LeapMotion JS library is a nice interface into a stream of frames, but often you need to keep track of the state of hands. Instead of rolling my own everytime, I wrote Levitate to provide a new Evented abstraction to managing the state of hands in my applications.

Dependencies

• Underscore
• EventEmitter

Usage

Wire up Levitate to capture the frames from the Leap.js loop

var lev = new Levitate();
Leap.loop(function(frame) {
    lev.handleFrame(frame);
});

Detect Incoming Hands

Instead of manually parsing the frames from Leap.js and keeping the state of hands, let Levitate do it for you.

lev.on('hand:new', function(id, hand){
    // id - id of incoming hand
    // hand - LevitateHand object (contains frame data for that hand)
});

Now that you have the ID of a new hand, register events to listen track just that hand alone.

lev.on('hand:new', function(id, hand){
    // id - id of incoming hand
    // hand - LevitateHand object (contains frame data for that hand)
    lev.on('hand:' + id + ':frame', function(hand) {
        // hand - LevitateHand object (contains frame data for that hand)
    });

    lev.on('hand:' + id + ':remove', function() {
        // Hand has left and will no longer be tracked.
        // Probably a good time to unbind some events
    });

});

Levitate will also let you know about what side of the LeapMotion the hand comes in on. Helpful for multihand applications. Here is an example of tracking new right hands.

lev.on('hand:new:right', function(id, hand){
    // id - id of incoming hand
    // hand - LevitateHand object (contains frame data for that hand)
    lev.on('hand:' + id + ':frame', function(hand) {
        // hand - LevitateHand object (contains frame data for that hand)
    });

    lev.on('hand:' + id + ':remove', function() {
        // Hand has left and will no longer be tracked.
        // Probably a good time to unbind some events
    });

});

TODO

• Add tests
• Pointer support without hands
• Gesture support