TWEEN.Interpolation

TWEEN.Interpolation = {

        Linear: function ( v, k ) {

                var m = v.length - 1, f = m * k, i = Math.floor( f ), fn = TWEEN.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: function ( v, k ) {

                var b = 0, n = v.length - 1, pw = Math.pow, bn = TWEEN.Interpolation.Utils.Bernstein, i;

                for ( i = 0; i <= n; i++ ) {
                        b += pw( 1 - k, n - i ) * pw( k, i ) * v[ i ] * bn( n, i );
                }

                return b;

        },

        CatmullRom: function ( v, k ) {

                var m = v.length - 1, f = m * k, i = Math.floor( f ), fn = TWEEN.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: function ( p0, p1, t ) {

                        return ( p1 - p0 ) * t + p0;

                },

                Bernstein: function ( n , i ) {

                        var fc = TWEEN.Interpolation.Utils.Factorial;
                        return fc( n ) / fc( i ) / fc( n - i );

                },

                Factorial: ( function () {

                        var a = [ 1 ];

                        return function ( n ) {

                                var s = 1, i;
                                if ( a[ n ] ) return a[ n ];
                                for ( i = n; i > 1; i-- ) s *= i;
                                return a[ n ] = s;

                        };

                } )(),

                CatmullRom: function ( p0, p1, p2, p3, t ) {

                        var v0 = ( p2 - p0 ) * 0.5, v1 = ( p3 - p1 ) * 0.5, t2 = t * t, t3 = t * t2;
                        return ( 2 * p1 - 2 * p2 + v0 + v1 ) * t3 + ( - 3 * p1 + 3 * p2 - 2 * v0 - v1 ) * t2 + v0 * t + p1;

                }

        }

};