WheelColliderSource-WheelFrictionCurveSource

The WheelFrictionCurveSource class provides a mapping of values from slip (x axis) to force (y axis). The function is a piecewise function constructed using two Hermite curves and a constant value.

I originally implemented the evaluation using the bisection method over the t [0, 1] values of the Hermite curves. I quickly realized however that the float precision was not high enough to handle the extreme values involved in the force axis (y). This forced me to implement an alternate method of sampling the curve, mainly taking a fixed number of samples across the curve (linearly increasing t) and storing the result in arrays which would later be searched and it's values linearly interpolated to give an approximation of the curve at a given slip axis (x). This resulted in very accurate results, what's more the error difference is minimal and can be decreased by using more samples or using a non linear sampling of t and over an amortized running time is more efficient.