A Two-Scale Microfacet Reflectance Model Combining Reflection and Diffraction

Nicolas Holzschuch 1 Romain Pacanowski 2, 3
1 MAVERICK - Models and Algorithms for Visualization and Rendering
Inria Grenoble - Rhône-Alpes, LJK - Laboratoire Jean Kuntzmann, INPG - Institut National Polytechnique de Grenoble
3 MANAO - Melting the frontiers between Light, Shape and Matter
LaBRI - Laboratoire Bordelais de Recherche en Informatique, Inria Bordeaux - Sud-Ouest, LP2N - Laboratoire Photonique, Numérique et Nanosciences
Abstract : Adequate reflectance models are essential for the production of photorealistic images. Microfacet reflectance models predict the appearance of a material at the macroscopic level based on microscopic surface details. They provide a good match with measured reflectance in some cases, but not always. This discrepancy between the behavior predicted by microfacet models and the observed behavior has puzzled researchers for a long time. In this paper, we show that diffraction effects in the micro-geometry provide a plausible explanation. We describe a two-scale reflectance model, separating between geometry details much larger than wavelength and those of size comparable to wavelength. The former model results in the standard Cook-Torrance model. The latter model is responsible for diffraction effects. Diffraction effects at the smaller scale are convolved by the micro-geometry normal distribution. The resulting two-scale model provides a very good approximation to measured reflectances.
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Submitted on : Wednesday, May 10, 2017 - 4:07:56 PM
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Nicolas Holzschuch, Romain Pacanowski. A Two-Scale Microfacet Reflectance Model Combining Reflection and Diffraction. ACM Transactions on Graphics, Association for Computing Machinery, 2017, 36 (4), pp.12. ⟨10.1145/3072959.3073621⟩. ⟨hal-01515948⟩



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