Abstract: A separable decomposition of bidirectional reflectance distributions (BRDFs) is used to implement arbitrary reflectances from point sources on existing graphics hardware. Two-dimensional texture mapping and compositing operations are used to reconstruct samples of the BRDF at every pixel at interactive rates.

A change of variables, the Gram-Schmidt halfangle/difference vector parameterization, improves separability in the case of glossy "microfacet" BRDFs. Two decomposition algorithms are also presented. The singular value decomposition (SVD) minimizes RMS error. The normalized decomposition is fast, simple, and online, using no more space than what is required for the final representation.