es6-tween
Version:
ES6 implementation of amazing tween.js
121 lines (76 loc) • 1.98 kB
JavaScript
const Interpolation = {
Linear( v, k ) {
const m = v.length - 1;
const f = m * k;
const i = Math.floor( f );
const fn = Interpolation.Utils.Linear;
if ( k < 0 ) {
return fn( v[ 0 ], v[ 1 ], f );
}
if ( k > 1 ) {
return fn( v[ m ], v[ m - 1 ], m - f );
}
return fn( v[ i ], v[ i + 1 > m ? m : i + 1 ], f - i );
},
Bezier( v, k ) {
let b = 0;
const n = v.length - 1;
const pw = Math.pow;
const bn = Interpolation.Utils.Bernstein;
for ( let i = 0; i <= n; i++ ) {
b += pw( 1 - k, n - i ) * pw( k, i ) * v[ i ] * bn( n, i );
}
return b;
},
CatmullRom( v, k ) {
const m = v.length - 1;
let f = m * k;
let i = Math.floor( f );
const fn = Interpolation.Utils.CatmullRom;
if ( v[ 0 ] === v[ m ] ) {
if ( k < 0 ) {
i = Math.floor( f = m * ( 1 + k ) );
}
return fn( v[ ( i - 1 + m ) % m ], v[ i ], v[ ( i + 1 ) % m ], v[ ( i + 2 ) % m ], f - i );
} else {
if ( k < 0 ) {
return v[ 0 ] - ( fn( v[ 0 ], v[ 0 ], v[ 1 ], v[ 1 ], -f ) - v[ 0 ] );
}
if ( k > 1 ) {
return v[ m ] - ( fn( v[ m ], v[ m ], v[ m - 1 ], v[ m - 1 ], f - m ) - v[ m ] );
}
return fn( v[ i ? i - 1 : 0 ], v[ i ], v[ m < i + 1 ? m : i + 1 ], v[ m < i + 2 ? m : i + 2 ], f - i );
}
},
Utils: {
Linear( p0, p1, t ) {
return ( p1 - p0 ) * t + p0;
},
Bernstein( n, i ) {
const fc = Interpolation.Utils.Factorial;
return fc( n ) / fc( i ) / fc( n - i );
},
Factorial: ( ( () => {
const a = [ 1 ];
return n => {
let s = 1;
if ( a[ n ] ) {
return a[ n ];
}
for ( let i = n; i > 1; i-- ) {
s *= i;
}
a[ n ] = s;
return s;
};
} ) )(),
CatmullRom( p0, p1, p2, p3, t ) {
const v0 = ( p2 - p0 ) * 0.5;
const v1 = ( p3 - p1 ) * 0.5;
const t2 = t * t;
const t3 = t * t2;
return ( 2 * p1 - 2 * p2 + v0 + v1 ) * t3 + ( -3 * p1 + 3 * p2 - 2 * v0 - v1 ) * t2 + v0 * t + p1;
}
}
}
export default Interpolation;