player/js/utils/bez.js

var bez = (function(){

    var easingFunctions = {};
    var storedBezierCurves = {};

    function pointOnLine2D(x1,y1, x2,y2, x3,y3){
        return Math.abs(((x2 - x1) * (y3 - y1)) - ((x3 - x1) * (y2 - y1))) < 0.0000001;
    }

    function getEasingCurve(encodedFuncName, coOrdArray) {
        coOrdArray = encodedFuncName;
        encodedFuncName = 'bez_' + coOrdArray.join('_').replace(/\./g, 'p');
        if(easingFunctions[encodedFuncName]){
            return easingFunctions[encodedFuncName];
        }
        var	polyBez = function(p1, p2) {
            var A = [null, null], B = [null, null], C = [null, null],
                bezCoOrd = function(t, ax) {
                    C[ax] = 3 * p1[ax], B[ax] = 3 * (p2[ax] - p1[ax]) - C[ax], A[ax] = 1 - C[ax] - B[ax];
                    return t * (C[ax] + t * (B[ax] + t * A[ax]));
                };
            return function(t) {
                var x = t, i = 0, z;
                while (++i < 14) {
                    z = bezCoOrd(x, 0) - t;
                    if (Math.abs(z) < 1e-3) break;
                    x -= z / (C[0] + x * (2 * B[0] + 3 * A[0] * x));
                }
                return bezCoOrd(x, 1);
            }
        };
        easingFunctions[encodedFuncName] = function(x, t, b, c, d) {
            return c * polyBez([coOrdArray[0], coOrdArray[1]], [coOrdArray[2], coOrdArray[3]])(t/d) + b;
        };
        return easingFunctions[encodedFuncName];
    }

    function drawBezierCurve(pt1,pt2,pt3,pt4){
        var bezierName = (pt1.join('_')+'_'+pt2.join('_')+'_'+pt3.join('_')+'_'+pt4.join('_')).replace(/\./g, 'p');
        if(storedBezierCurves[bezierName]){
            return storedBezierCurves[bezierName];
        }
        var curveSegments = 500, absToCoord, absTiCoord;
        var k;
        var i, len;
        var triCoord1,triCoord2,triCoord3,liCoord1,liCoord2,ptCoord,perc,addedLength = 0;
        var ptDistance;
        var point,lastPoint = null;
        var bezierData = {
            points :[],
            segmentLength: 0
        };
        if(pointOnLine2D(pt1[0],pt1[1],pt2[0],pt2[1],pt1[0]+pt3[0],pt1[1]+pt3[1])
            && pointOnLine2D(pt1[0],pt1[1],pt2[0],pt2[1],pt2[0]+pt4[0],pt2[1]+pt4[1])){
            curveSegments = 2;
        }
        for(k=0;k<curveSegments;k+=1){
            point = [];
            perc = k/(curveSegments-1);
            ptDistance = 0;
            absToCoord = [];
            absTiCoord = [];
            len = pt3.length;
            for(i=0;i<len;i+=1){
                if(absToCoord[i] == null){
                    absToCoord[i] = pt1[i] + pt3[i];
                    absTiCoord[i] = pt2[i] + pt4[i];
                }
                triCoord1 = pt1[i] + (absToCoord[i] - pt1[i])*perc;
                triCoord2 = absToCoord[i] + (absTiCoord[i] - absToCoord[i])*perc;
                triCoord3 = absTiCoord[i] + (pt2[i] - absTiCoord[i])*perc;
                liCoord1 = triCoord1 + (triCoord2 - triCoord1)*perc;
                liCoord2 = triCoord2 + (triCoord3 - triCoord2)*perc;
                ptCoord = liCoord1 + (liCoord2 - liCoord1)*perc;
                point.push(ptCoord);
                if(lastPoint !== null){
                    ptDistance += Math.pow(point[i] - lastPoint[i],2);
                }
            }
            ptDistance = Math.sqrt(ptDistance);
            addedLength += ptDistance;
            bezierData.points.push({partialLength: ptDistance, point: point});
            lastPoint = point;
        }
        bezierData.segmentLength = addedLength;
        storedBezierCurves[bezierName] = bezierData;
        return bezierData;
    }

    function buildBezierData(keyData){
        keyData.bezierData = drawBezierCurve(keyData.s,keyData.e,keyData.to,keyData.ti);
    }

    var ob = {
        getEasingCurve : getEasingCurve,
        drawBezierCurve : drawBezierCurve,
        buildBezierData : buildBezierData
    };

    return ob;
}());