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Computational Visual Media 2020, 6(1): 37-51 https://doi.org/10.1007/s41095-020-0160-1
Research Article | Open Access | Issue | Published: 23 March 2020

A practical path guiding method for participating media

Show Author's Information Hong Deng1,  Beibei Wang1( ),  Rui Wang2,  Nicolas Holzschuch3
Nanjing University of Science and Technology, Nanjing 210094, China.
State Key Lab of CAD&CG, Zhejiang University, Hangzhou 310058, China.
Univ. Grenoble-Alpes, Inria, CNRS, Grenoble INP, LJK, 38000 Grenoble, France.
Keywords:
Monte Carlo, ray tracing, path guiding, volume light transport, participating media, rendering
Cite this article:
Deng H, Wang B, Wang R, et al. A practical path guiding method for participating media. Computational Visual Media, 2020, 6(1): 37-51. https://doi.org/10.1007/s41095-020-0160-1
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Abstract Full text Electronic supplementary material About this article

Rendering translucent materials is costly: light transport algorithms need to simulate a large number of scattering events inside the material before reaching convergence. The cost is especially high for materials with a large albedo or a small mean-free-path, where higher-order scattering effects dominate. In simple terms, the paths get lost in the medium. Path guiding has been proposed for surface rendering to make convergence faster by guiding the sampling process. In this paper, we introduce a path guiding solution for translucent materials. We learn an adaptive approximate representation of the radiance distribution in the volume and use it to sample the scattering direction, combining it with phase function sampling by resampled importance sampling. The proposed method significantly improves the performance of light transport simulation in participating media, especially for small lights and media with refractive boundaries. Our method can handle any homogeneous participating medium, with high or low scattering, with high or low absorption, and from isotropic to highly anisotropic.


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About this article

A practical path guiding method for participating media

Show Author's information Hong Deng1, Beibei Wang1( ), Rui Wang2, Nicolas Holzschuch3
Nanjing University of Science and Technology, Nanjing 210094, China.
State Key Lab of CAD&CG, Zhejiang University, Hangzhou 310058, China.
Univ. Grenoble-Alpes, Inria, CNRS, Grenoble INP, LJK, 38000 Grenoble, France.

Abstract

Rendering translucent materials is costly: light transport algorithms need to simulate a large number of scattering events inside the material before reaching convergence. The cost is especially high for materials with a large albedo or a small mean-free-path, where higher-order scattering effects dominate. In simple terms, the paths get lost in the medium. Path guiding has been proposed for surface rendering to make convergence faster by guiding the sampling process. In this paper, we introduce a path guiding solution for translucent materials. We learn an adaptive approximate representation of the radiance distribution in the volume and use it to sample the scattering direction, combining it with phase function sampling by resampled importance sampling. The proposed method significantly improves the performance of light transport simulation in participating media, especially for small lights and media with refractive boundaries. Our method can handle any homogeneous participating medium, with high or low scattering, with high or low absorption, and from isotropic to highly anisotropic.

Keywords: Monte Carlo, ray tracing, path guiding, volume light transport, participating media, rendering

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Publication history

Revised: 06 February 2020
Accepted: 19 February 2020
Published: 23 March 2020
Issue date: March 2020

Copyright

© The author(s) 2020

Acknowledgements

We thank the reviewers for their valuable comments. This work was partially supported by the National Key R&D Program of China under Grant No. 2017YFB0203000, the National Natural Science Foundation of China under Grant Nos. 61802187 and 61872223, the Natural Science Foundationof Jiangsu under Grant No. BK20170857, the fundamental research funds for the central universities No. 30918011320, and ANR project ANR-15-CE38-0005 "Materials" .

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