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danielsuo/TWEEN Easing

Created December 21, 2013 01:55
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TWEEN Easing
TWEEN.Easing = {
Linear: {
None: function ( k ) {
return k;
}
},
Quadratic: {
In: function ( k ) {
return k * k;
},
Out: function ( k ) {
return k * ( 2 - k );
},
InOut: function ( k ) {
if ( ( k *= 2 ) < 1 ) return 0.5 * k * k;
return - 0.5 * ( --k * ( k - 2 ) - 1 );
}
},
Cubic: {
In: function ( k ) {
return k * k * k;
},
Out: function ( k ) {
return --k * k * k + 1;
},
InOut: function ( k ) {
if ( ( k *= 2 ) < 1 ) return 0.5 * k * k * k;
return 0.5 * ( ( k -= 2 ) * k * k + 2 );
}
},
Quartic: {
In: function ( k ) {
return k * k * k * k;
},
Out: function ( k ) {
return 1 - ( --k * k * k * k );
},
InOut: function ( k ) {
if ( ( k *= 2 ) < 1) return 0.5 * k * k * k * k;
return - 0.5 * ( ( k -= 2 ) * k * k * k - 2 );
}
},
Quintic: {
In: function ( k ) {
return k * k * k * k * k;
},
Out: function ( k ) {
return --k * k * k * k * k + 1;
},
InOut: function ( k ) {
if ( ( k *= 2 ) < 1 ) return 0.5 * k * k * k * k * k;
return 0.5 * ( ( k -= 2 ) * k * k * k * k + 2 );
}
},
Sinusoidal: {
In: function ( k ) {
return 1 - Math.cos( k * Math.PI / 2 );
},
Out: function ( k ) {
return Math.sin( k * Math.PI / 2 );
},
InOut: function ( k ) {
return 0.5 * ( 1 - Math.cos( Math.PI * k ) );
}
},
Exponential: {
In: function ( k ) {
return k === 0 ? 0 : Math.pow( 1024, k - 1 );
},
Out: function ( k ) {
return k === 1 ? 1 : 1 - Math.pow( 2, - 10 * k );
},
InOut: function ( k ) {
if ( k === 0 ) return 0;
if ( k === 1 ) return 1;
if ( ( k *= 2 ) < 1 ) return 0.5 * Math.pow( 1024, k - 1 );
return 0.5 * ( - Math.pow( 2, - 10 * ( k - 1 ) ) + 2 );
}
},
Circular: {
In: function ( k ) {
return 1 - Math.sqrt( 1 - k * k );
},
Out: function ( k ) {
return Math.sqrt( 1 - ( --k * k ) );
},
InOut: function ( k ) {
if ( ( k *= 2 ) < 1) return - 0.5 * ( Math.sqrt( 1 - k * k) - 1);
return 0.5 * ( Math.sqrt( 1 - ( k -= 2) * k) + 1);
}
},
Elastic: {
In: function ( k ) {
var s, a = 0.1, p = 0.4;
if ( k === 0 ) return 0;
if ( k === 1 ) return 1;
if ( !a || a < 1 ) { a = 1; s = p / 4; }
else s = p * Math.asin( 1 / a ) / ( 2 * Math.PI );
return - ( a * Math.pow( 2, 10 * ( k -= 1 ) ) * Math.sin( ( k - s ) * ( 2 * Math.PI ) / p ) );
},
Out: function ( k ) {
var s, a = 0.1, p = 0.4;
if ( k === 0 ) return 0;
if ( k === 1 ) return 1;
if ( !a || a < 1 ) { a = 1; s = p / 4; }
else s = p * Math.asin( 1 / a ) / ( 2 * Math.PI );
return ( a * Math.pow( 2, - 10 * k) * Math.sin( ( k - s ) * ( 2 * Math.PI ) / p ) + 1 );
},
InOut: function ( k ) {
var s, a = 0.1, p = 0.4;
if ( k === 0 ) return 0;
if ( k === 1 ) return 1;
if ( !a || a < 1 ) { a = 1; s = p / 4; }
else s = p * Math.asin( 1 / a ) / ( 2 * Math.PI );
if ( ( k *= 2 ) < 1 ) return - 0.5 * ( a * Math.pow( 2, 10 * ( k -= 1 ) ) * Math.sin( ( k - s ) * ( 2 * Math.PI ) / p ) );
return a * Math.pow( 2, -10 * ( k -= 1 ) ) * Math.sin( ( k - s ) * ( 2 * Math.PI ) / p ) * 0.5 + 1;
}
},
Back: {
In: function ( k ) {
var s = 1.70158;
return k * k * ( ( s + 1 ) * k - s );
},
Out: function ( k ) {
var s = 1.70158;
return --k * k * ( ( s + 1 ) * k + s ) + 1;
},
InOut: function ( k ) {
var s = 1.70158 * 1.525;
if ( ( k *= 2 ) < 1 ) return 0.5 * ( k * k * ( ( s + 1 ) * k - s ) );
return 0.5 * ( ( k -= 2 ) * k * ( ( s + 1 ) * k + s ) + 2 );
}
},
Bounce: {
In: function ( k ) {
return 1 - TWEEN.Easing.Bounce.Out( 1 - k );
},
Out: function ( k ) {
if ( k < ( 1 / 2.75 ) ) {
return 7.5625 * k * k;
} else if ( k < ( 2 / 2.75 ) ) {
return 7.5625 * ( k -= ( 1.5 / 2.75 ) ) * k + 0.75;
} else if ( k < ( 2.5 / 2.75 ) ) {
return 7.5625 * ( k -= ( 2.25 / 2.75 ) ) * k + 0.9375;
} else {
return 7.5625 * ( k -= ( 2.625 / 2.75 ) ) * k + 0.984375;
}
},
InOut: function ( k ) {
if ( k < 0.5 ) return TWEEN.Easing.Bounce.In( k * 2 ) * 0.5;
return TWEEN.Easing.Bounce.Out( k * 2 - 1 ) * 0.5 + 0.5;
}
}
};
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