Real surfaces often exhibit both specular (mirror-like) and matte
behavior. In many scientific fields this behavior is approximated by
the "Lambertian-specular" model, where a linear combination of
Lambertian and ideal specular reflection is assumed. While this
approximation is useful, it does not capture the dramatic surface
appearance for acute and near-perpendicular viewing angles. The model
presented in this paper does capture these angle-dependent behavior
changes by allowing the matte and specular coefficients to co-vary.
Furthermore, this modified matte-specular model uses a non-Lambertian
matte term to maintain reciprocity of the bidirectional reflectance
distribution function (BRDF), an important point for many rendering
engines. Finally, this model maintains the simplicity of the
traditional models.
A gzipped postscript version of the paper is available
here.
A pdf version of the paper is available
here.
