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Resampling-aware Weighting Functions for Bidirectional Path Tracing Using Multiple Light Sub-Paths

delete2020-03-03
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K
Kei Iwasaki
Y
Yoshinori Dobashi
DOI:10.1145/3338994delete
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Abstract

Abstract

En 中文
Bidirectional path tracing (BPT) with multiple importance sampling (MIS) is a popular technique for rendering realistic images. Recently, it has been shown that BPT can be improved by preparing multiple light sub-paths and by resampling a small number of light sub-paths from them to generate full paths with large contribution. Traditionally, for MIS weights, the balance heuristic has widely been used to minimize the upper bound of variance, where each full path is weighted in proportion to the probability of the path. Although the probability of the path can change due to the resampling process, the weighting functions used in the previous methods remain unaffected by the change in probability, resulting in less efficiency. To address this problem, we propose new weighting functions for BPT with multiple light sub-paths. Our main contribution is a precise formulation of the variance and the derivation of the weighting functions that can appropriately treat the change in probability. We demonstrate that our weighting functions significantly improve the image quality. We will release a simple version of our implementation as open source to ensure reproducibility.
Keywords:
Bidirectional path tracing
multiple importance sampling
resampling importance sampling
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Journal

ACM Transactions on Graphics cover
ACM Transactions on Graphics
IF:
9.5
Papers:
4.7K
Citations:
3.6W

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Hokkaido University
Scholars:
3.6W
Papers: 2.5W
Citations: 2.6W
Wakayama University cover
Wakayama University
Scholars:
373
Papers: 336
Citations: 190