tween.js

ig.module(
	'plugins.tween'
).requires(
	'impact.impact'
).defines((function(){ 'usestrict';

var Tween = window.Tween = ig.Class.extend({

	init: function(options){
		// from, to, duration, tween
		this.from     = options.from;
		this.to       = options.to;
		this.duration = options.duration || 2000;
		this.tween    = options.tween || Tween.TYPES.EASE_IN_OUT_SINE;
		this.callback = options.callback;
		this.timer    = new ig.Timer();
	},

	getValue: function(){
		var delta = this.timer.delta() * 1000;

		return delta >= this.duration ? this.to : this.tween(
			delta,
			this.from,
			this.to - this.from,
			this.duration
		);
	}

});

Tween.TYPES = {

	LINEAR: function (t, b, c, d) {
		return c*t/d + b;
	},

	EASE_IN_SINE: function (t, b, c, d) {
		return c * (1 - Math.cos(t/d * (Math.PI/2))) + b;
	},

	EASE_OUT_SINE: function (t, b, c, d) {
		return c * Math.sin(t/d * (Math.PI/2)) + b;
	},

	EASE_IN_OUT_SINE: function (t, b, c, d) {
		return c/2 * (1 - Math.cos(Math.PI*t/d)) + b;
	},

	EASE_IN_QUAD: function (t, b, c, d) {
		return c*(t/=d)*t + b;
	},

	EASE_OUT_QUAD: function (t, b, c, d) {
		return -c * (t/=d)*(t-2) + b;
	},

	EASE_IN_OUT_QUAD: function (t, b, c, d) {
		if ((t/=d/2) < 1) return c/2*t*t + b;
		return -c/2 * ((--t)*(t-2) - 1) + b;
	},

	EASE_IN_CIRC: function (t, b, c, d) {
		return c * (1 - Math.sqrt(1 - (t/=d)*t)) + b;
	},

	EASE_OUT_CIRC: function (t, b, c, d) {
		return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
	},

	EASE_IN_OUT_CIRC: function (t, b, c, d) {
		if ((t/=d/2) < 1)
			return c/2 * (1 - Math.sqrt(1 - t*t)) + b;
		return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
	},

	EASE_IN_EXPO: function (t, b, c, d) {
		return c * Math.pow(2, 10 * (t/d - 1)) + b;
	},

	EASE_OUT_EXPO: function (t, b, c, d) {
		return c * (-Math.pow(2, -10 * t/d) + 1) + b;
	},

	EASE_IN_OUT_EXPO: function (t, b, c, d) {
		if ((t/=d/2) < 1)
			return c/2 * Math.pow(2, 10 * (t - 1)) + b;
		return c/2 * (-Math.pow(2, -10 * --t) + 2) + b;
	},

	EASE_IN_QUINT: function (t, b, c, d) {
		return c * Math.pow (t/d, 5) + b;
	},

	EASE_OUT_QUINT: function (t, b, c, d) {
		return c * (Math.pow (t/d-1, 5) + 1) + b;
	},

	EASE_IN_OUT_QUINT: function (t, b, c, d) {
		if ((t/=d/2) < 1)
			return c/2 * Math.pow (t, 5) + b;
		return c/2 * (Math.pow (t-2, 5) + 2) + b;
	},

	EASE_IN_QUART: function (t, b, c, d) {
		return c * Math.pow (t/d, 4) + b;
	},

	EASE_OUT_QUART: function (t, b, c, d) {
		return -c * (Math.pow (t/d-1, 4) - 1) + b;
	},

	EASE_IN_OUT_QUART: function (t, b, c, d) {
		if ((t/=d/2) < 1)
			return c/2 * Math.pow (t, 4) + b;
		return -c/2 * (Math.pow (t-2, 4) - 2) + b;
	},

	EASE_IN_CUBIC: function (t, b, c, d) {
		return c * Math.pow (t/d, 3) + b;
	},

	EASE_OUT_CUBIC: function (t, b, c, d) {
		return c * (Math.pow (t/d-1, 3) + 1) + b;
	},

	EASE_IN_OUT_CUBIC: function (t, b, c, d) {
		if ((t/=d/2) < 1)
			return c/2 * Math.pow (t, 3) + b;
		return c/2 * (Math.pow (t-2, 3) + 2) + b;
	}
};

}).bind(this));