lcIllumination.h
incudes a bunch of illumination models and useful shading tools, mostly form 'The Renderman Shading Language Guide' by Rudy Cortes
shadingnormal - pixars faceforward util
lcSchlickFresnel - a fresnel approximation
lcFresnel - a full on fresnel function
lcOrenNayar - a nice diffuse shading model
lcSeeliger
lcDiffuseWrap
lcDiffuseBias
lcSpecPhong
lcSpecGlossy - glossy ceramic like model
lcSpecSchlick
lcSpecWestinMetal
lcGather - raytracing using 'gather', also supports a env map where ray is null
lcEnv - environment mapping
