Non-linear approximation of reflectance functions
Eric P. Lafortune, Sing-Choong Foo, Kenneth E. Torrance, Donald P. Greenberg · 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.