Method ComputeLengthNorm

Implemented as:

1/sqrt( steepness * (Math.Abs(x-min) + Math.Abs(x-max) - (max-min)) + 1 )

.

This degrades to

1/Math.Sqrt(x)

when min and max are both 1 and steepness is 0.5

:TODO: potential optimization is to just flat out return 1.0f if numTerms is between min and max.

public virtual float ComputeLengthNorm(int numTerms)