**Neumann László, Neumann Attila, Szirmay-Kalos László
Department of Control Engineering and Information Technology, Technical University of Budapest,
Budapest, Muegyetem rkp. 11, H-1111, HUNGARY
szirmay@fsz.bme.hu
**

**Abstract:**

We introduce a physically plausible mathematical model for a large class of BRDFs. The new model is as simple as the well-known Phong model, but eliminates its disadvantages. It gives a good visual approximation for a lot of practical materials: coated metals, plastics, ceramics, retro-reflective paints, anisotropic materials, etc. %As limiting cases the new model also includes %the ideal diffuse model and ideal mirror. Because of its illustrative properties it can be used easily in most commercial software and because of its low computational cost it is practical for VR. The model is based on a special basic BRDF definition, which meets the requirements of reciprocity and of energy conservation. Then a class of BRDFs is constructed from this basic BRDF with different weight functions. The definition of such weight functions requires the user to specify the profile of the highlights, from which the weight function is obtained by derivation. It is also demonstrated how importance sampling can be used with the new BRDFs.

**Keywords:**

Rendering, reflection models, BRDF, albedo, anisotropy, retro-reflective models,
coated metals, energy mirror, Monte Carlo, importance sampling.