Function Kochanek_Bartels_Spline

See http://en.wikipedia.org/wiki/Kochanek-Bartels_curves Tension: -1 = Round -> 1 = Tight Bias: -1 = Pre-shoot (bias left) -> 1 = Post-shoot (bias right) Continuity: -1 = Box corners -> 1 = Inverted corners If T=B=C=0 it's the same matrix as Catmull-Rom. If T=1 & B=C=0 it's the same as Cubic. If T=B=0 & C=-1 it's just linear interpolation See http://news.povray.org/povray.binaries.tutorial