Cornell University Program of Computer Graphics
Non-linear approximation of reflectance functions.Eric P. F. Lafortune, Sing-Choong Foo, Kenneth E. Torrance, and Donald P. Greenberg.
In Turner Whitted, editor, SIGGRAPH 97 Conference Proceedings, Annual Conference Series, pages 117--126. ACM SIGGRAPH, Addison Wesley, August 1997.
We introduce a new class of primitive functions with non-linear parameters for representing light reflectance functions. The functions are reciprocal, energy-conserving and expressive. They can capture important phenomena such as off-specular reflection, increasing reflectance and retro-reflection. We demonstrate this by fitting sums of primitive functions to a physically-based model and to actual measurements. The resulting representation is simple, compact and uniform. It can be applied efficiently in analytical and Monte Carlo computations.
This paper is available as a PDF file LFTG97.pdf (1.4M).