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DTSTAMP:20240214T070245Z
LOCATION:Meeting Room C4.8\, Level 4 (Convention Centre)
DTSTART;TZID=Australia/Melbourne:20231213T164000
DTEND;TZID=Australia/Melbourne:20231213T165000
UID:siggraphasia_SIGGRAPH Asia 2023_sess146_papers_574@linklings.com
SUMMARY:Multiple-bounce Smith Microfacet BRDFs using the Invariance Princi
 ple
DESCRIPTION:Technical Communications, Technical Papers\n\nYuang Cui (Anhui
  Science and Technology University); Gaole Pan and Jian Yang (Nanjing Univ
 ersity of Science and Technology); Lei Zhang (The Hong Kong Polytechnic Un
 iversity); Ling-Qi Yan (University of California, University of California
  Santa Barbara); and Beibei Wang (Nankai University, Nanjing University of
  Science and Technology)\n\nSmith microfacet models are widely used in com
 puter graphics to represent materials. Traditional microfacet models do no
 t consider the multiple bounces on microgeometries, leading to visible ene
 rgy missing, especially on rough surfaces. Later, as the equivalence betwe
 en the microfacets and volume has been revealed, random walk solutions hav
 e been proposed to introduce multiple bounces, but at the cost of high var
 iance. Recently, the position-free property has been introduced into the m
 ultiple-bounce model, resulting in much less noise, but also bias or a com
 plex derivation. In this paper, we propose a simple way to derive the mult
 iple-bounce Smith microfacet bidirectional reflectance distribution functi
 ons (BRDFs) using the invariance principle. At the core of our model is a 
 shadowing-masking function for a path consisting of direction collections,
  rather than separated bounces. Our model ensures unbiasedness and can pro
 duce less noise compared to the previous work with equal time, thanks to t
 he simple formulation. Furthermore, we also propose a novel probability de
 nsity function (PDF) for BRDF multiple importance sampling, which has a be
 tter match with the multiple-bounce BRDFs, producing less noise than previ
 ous naive approximations.\n\nRegistration Category: Full Access\n\nSession
  Chair: Hongzhi Wu (Zhejiang University; State Key Lab of CAD and CG, Zhej
 iang University)
URL:https://asia.siggraph.org/2023/full-program?id=papers_574&sess=sess146
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