34 function keySpline (mX1, mY1, mX2, mY2) {
36 this.
get =
function(aX) {
37 if (mX1 == mY1 && mX2 == mY2)
return aX;
38 return CalcBezier(GetTForX(aX), mY1, mY2);
41 function A(aA1, aA2) {
return 1.0 - 3.0 * aA2 + 3.0 * aA1; }
42 function B(aA1, aA2) {
return 3.0 * aA2 - 6.0 * aA1; }
43 function C(aA1) {
return 3.0 * aA1; }
46 function CalcBezier(aT, aA1, aA2) {
47 return ((A(aA1, aA2)*aT + B(aA1, aA2))*aT + C(aA1))*aT;
51 function GetSlope(aT, aA1, aA2) {
52 return 3.0 * A(aA1, aA2)*aT*aT + 2.0 * B(aA1, aA2) * aT + C(aA1);
55 function GetTForX(aX) {
58 for (var i = 0; i < 4; ++i) {
59 var currentSlope = GetSlope(aGuessT, mX1, mX2);
60 if (currentSlope == 0.0)
return aGuessT;
61 var currentX = CalcBezier(aGuessT, mX1, mX2) - aX;
62 aGuessT -= currentX / currentSlope;