Martin Šik
Charles University in Prague
Hisanari Otsu
The University of Tokyo
Toshiya Hachisuka
The University of Tokyo
Jaroslav Křivánek
Charles University in Prague

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We present a robust light transport simulation algorithm that fuses key ideas behind vertex connection and merging/unified path sampling (VCM/UPS) [Georgiev et al. 2012; Hachisuka et al. 2012] and Markov chain Monte Carlo methods. It outperforms state-of-the-art approaches, such as VCM/UPS or Metropolis light transport with manifold exploration (MEMLT) [Jakob and Marschner 2012], especially in scenes with complex glossy or specular transport and complex visibility. At the same time, the algorithm is substantially simpler than many of the recent Metropolis light transport variants.


Efficiently simulating light transport in various scenes with a single algorithm is a difficult and important problem in computer graphics. Two major issues have been shown to hinder the efficiency of the existing solutions: light transport due to multiple highly glossy or specular interactions, and scenes with complex visibility between the camera and light sources. While recent bidirectional path sampling methods such as vertex connection and merging/unified path sampling (VCM/UPS) efficiently deal with highly glossy or specular transport, they tend to perform poorly in scenes with complex visibility. On the other hand, Markov chain Monte Carlo (MCMC) methods have been able to show some excellent results in scenes with complex visibility, but they behave unpredictably in scenes with glossy or specular surfaces due to their fundamental issue of sample correlation. In this paper, we show how to fuse the underlying key ideas behind VCM/UPS and MCMC into a single, efficient light transport solution. Our algorithm is specifically designed to retain the advantages of both approaches, while alleviating their limitations. Our experiments show that the algorithm can efficiently render scenes with both highly glossy or specular materials and complex visibility, without compromising the performance in simpler cases.


Martin Šik, Hisanari Otsu, Toshiya Hachisuka, Jaroslav Křivánek:
Robust light transport simulation via metropolised bidirectional estimators (Proceedings of SIGGRAPH Asia), 35(6), 2016

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We would like to thank the reviewers for their insightful comments, and Wenzel Jakob for his rendering software Mitsuba, and Johannes Hanika and Anton S. Kaplanyan for their help with setting up half vector space light transport algorithm.
The work was supported by Charles University in Prague, project GA UK 164815, by the grant SVV–2016–260332, by the Czech Science Foundation grant 16–18964S, and by the JSPS KAKENHI Grant Number 15H05308.