Notes on the ward brdf.

Technical report PCG-05-06, Program of Computer Graphics, Cornell University, April 2005.

The anisotropic BRDF introduced in [Ward 1992] has become widely used in computer graphics, but some important implementation details are less widely known. We discuss how to efficiently evaluate the Ward BRDF. Then we derive the probability density function for its associated Monte Carlo sampling scheme and the correct weights to use with the generated samples. Finally for the isotropic version, we describe how to bound the maximum possible BRDF value over a region of (direction) space.

This paper is available as a PDF file Wal05.pdf (710K).