2014/10/15 下午 10:04:34

iphone Programming Glossary: beziertangent

Find the tangent of a point on a cubic bezier curve (on an iPhone)

http://stackoverflow.com/questions/4089443/find-the-tangent-of-a-point-on-a-cubic-bezier-curve-on-an-iphone

It draws approxidistant points along the curve and it draws the tangents. bezierInterpolation finds the points and bezierTangent finds the tangents There is also an alternate version of Michal's answer which is more explanatory . To repeat bezierInterpolation.. You can use either routine bezierInterpolation or altBezierInterpolation for identical results. In both cases use bezierTangent to find the tangents. Finally at the bottom is a code block containing only the two routines you need for the calculation.. a little clearer CGFloat t2 t t CGFloat t3 t2 t return a a 3 t 3 a a t t 3 b t 6 b b 3 t t c 3 c 3 t t2 d t3 CGFloat bezierTangent CGFloat t CGFloat a CGFloat b CGFloat c CGFloat d note that abcd are aka x0 x1 x2 x3 the four coefficients .. A x3 3 x2..

How do I detect a touch on a UIBezierPath and move a ball along that?

http://stackoverflow.com/questions/4854035/how-do-i-detect-a-touch-on-a-uibezierpath-and-move-a-ball-along-that

3.0 c 3.0 b a CGFloat C2 3.0 c 6.0 b 3.0 a CGFloat C3 3.0 b 3.0 a CGFloat C4 a return C1 t t t C2 t t C3 t C4 CGFloat bezierTangent CGFloat t CGFloat a CGFloat b CGFloat c CGFloat d CGFloat C1 d 3.0 c 3.0 b a CGFloat C2 3.0 c 6.0 b 3.0 a CGFloat C3 3.0..