clamptosphere expression function

Clamps a vector to always end between a minimum and maximum sphere.

This function computes a vector R that is parallel to the given (x,y,z) vector. R is adjusted so that its magnitude is always between the min and max radii (i.e min_radius ≤ |R| ≤ max_radius)

This function returns one of the components of the vector R according to the value of constant_type: “X”, “Y” or “Z”.