Shrimp Shader Generator FLTK2 GUI (SVN)

Added a comment in the extras header to clear some confusion. The he_torrance geometric self-shadowing/masking function is the full Smith expression for geometric self-shadowing/masking, as used in the He-Torrance model. The Smith function is an approximation as used in the Torrance-Sparrow model. Note that Christophe Schlick has another similar approximation to the full Smith expression.
Added the initial revision of the sampling headers. This has the Schlick, Ward, Ashikhmin-Shirley (all isotropic & anisotropic), and the Phong and Beckmann distributions. Respective blocks for these are included.