Spherical harmonics transformations, projections, convolutions, and utility functions. Used for environment map processing.
I have code for the fast transform (in addition to the discrete here) that I will add sometime.
Consult the following papers for insight:
Spherical Harmonic Lighting: The Gritty Details
A Fast Transform For Spherical Harmonics
Spherical Harmonics - Volker Schönefeld
An Efficient Representation for Irradiance Environment Maps
Frequency Space Environment Map Rendering
