:DESCRIPTION:
Oren Nayar shader is based on the research paper "Generalization of Lambert's Reflectance Model". The shader is based on a more physical approach to shading rough surfaces, and considers rough surfaces to have microscopic grooves and hills. Unlike the conventional Lambert shader that assumes its a smooth surface that reflects light equally. It has a roughness parameter that when placed at zero is the default Lambert shading. When higher values are inputted the surface becomes rougher and absorbing more light. While reflecting the light at the glancing angles.