UBC Theses and Dissertations
Local illumination models from surface geometry microform Huo, Gang
In this thesis, we propose a model to simulate the small-scale geometry of cloth and develop a method to derive the BRDF (Bidirectional Reflectance-Distribution Function) of this model from the underlying surface geometry, taking into account the blocking and shadowing phenomena at the small scale. Sample images of cloth generated with this BRDF look highly realistic. As a starting point to the inter-reflection problem, we examine the secondary reflection phenomena on the surface model made of parallel cylinders (as proposed by Poulin and Fournier) and the model proposed here for cloth. Two solutions are presented sampling through raytracing and an analytical approximation. The results convincingly indicate that the intensity from multiply reflected light could be substantial for bumped surfaces with low specular exponent n. Therefore inter-reflection should be accounted for in the lighting model for these surfaces. Generated cloth images including secondary reflection effects exhibit a higher degree of realism. The computation of secondary reflection effects is however quite expensive. The techniques presented can be extended to extract macroscopic reflection behaviour from the knowledge of the microscopic geometric structure.
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