Bi-Scale Radiance Transfer
Peter-Pike Sloan, Xinguo Liu, Heung-Yeung Shum, John Snyder
In ACM Transactions on Graphics, 22(3), July 2003.
Abstract: Radiance transfer represents how generic source lighting is shadowed and scattered by an object to produce view-dependent appearance. We generalize by rendering transfer at two scales. A macro-scale is coarsely sampled over an object's surface, providing global effects like shadows cast from an arm onto a body. A meso-scale is finely sampled over a small patch to provide local texture. Low-order (25D) spherical harmonics represent lowfrequency lighting dependence for both scales. To render, a coefficient vector representing distant source lighting is first transformed at the macro-scale by a matrix at each vertex of a coarse mesh. The resulting vectors represent a spatially-varying hemisphere of lighting incident to the meso-scale. A 4D function, called a radiance transfer texture (RTT), then specifies the surface's meso-scale response to each lighting basis component, as a function of a spatial index and a view direction. Finally, a 25D dot product of the macro-scale result vector with the vector looked up from the RTT performs the correct shading integral. We use an id map to place RTT samples from a small patch over the entire object; only two scalars are specified at high spatial resolution. Results show that bi-scale decomposition makes preprocessing practical and efficiently renders self-shadowing and interreflection effects from dynamic, low-frequency light sources at both scales.
Keyword(s): Keywords: Graphics Hardware, Illumination, Monte Carlo Techniques,Rendering, Shadow Algorithms
@article{Sloan:2003:BRT,
author = {Peter-Pike Sloan and Xinguo Liu and Heung-Yeung Shum and John Snyder},
title = {Bi-Scale Radiance Transfer},
journal = {ACM Transactions on Graphics},
volume = {22},
number = {3},
pages = {370--375},
month = jul,
year = {2003},
}
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