Position-free multiple-bounce computations for smith microfacet BSDFs - Inria - Institut national de recherche en sciences et technologies du numérique Access content directly
Journal Articles ACM Transactions on Graphics Year : 2022

Position-free multiple-bounce computations for smith microfacet BSDFs


Bidirectional Scattering Distribution Functions (BSDFs) encode how a material reflects or transmits the incoming light. The most commonly used model is the microfacet BSDF. It computes the material response from the microgeometry of the surface assuming a single bounce on specular microfacets. The original model ignores multiple bounces on the microgeometry, resulting in an energy loss, especially for rough materials. In this paper, we present a new method to compute the multiple bounces inside the microgeometry, eliminating this energy loss. Our method relies on a position-free formulation of multiple bounces inside the microgeometry. We use an explicit mathematical definition of the path space that describes single and multiple bounces in a uniform way. We then study the behavior of light on the different vertices and segments in the path space, leading to a reciprocal multiple-bounce description of BSDFs. Furthermore, we present practical, unbiased Monte Carlo estimators to compute multiple scattering. Our method is less noisy than existing algorithms for computing multiple scattering. It is almost noise-free with a very-low sampling rate, from 2 to 4 samples per pixel (spp).

Dates and versions

hal-03937876 , version 1 (13-01-2023)





Beibei Wang, Wenhua Jin, Jiahui Fan, Jian Yang, Nicolas Holzschuch, et al.. Position-free multiple-bounce computations for smith microfacet BSDFs. ACM Transactions on Graphics, 2022, 41 (4), pp.1-14. ⟨10.1145/3528223.3530112⟩. ⟨hal-03937876⟩
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