“Bidirectional Path Tracing Using Backward Stochastic Light Culling”

  • ©Yusuke Tokuyoshi and Takahiro Harada

  • ©Yusuke Tokuyoshi and Takahiro Harada

  • ©Yusuke Tokuyoshi and Takahiro Harada


Entry Number: 72


    Bidirectional Path Tracing Using Backward Stochastic Light Culling



    Bidirectional path tracing (BPT) produces noticeable variance for specular-diffuse-specular reflections even if they are not perfectly specular. This is because sampling of the connection between a light vertex and eye vertex does not take bidirectional reflectance distribution functions (BRDFs) into account. This paper presents a novel unbiased sampling method referred to as backward stochastic light culling which addresses the problem of specular-diffuse-glossy reflections. Our method efficiently performs Russian roulette for many light vertices according to the glossy BRDF at a given eye vertex using a hierarchical culling algorithm. We combine our method with light vertex cache-based BPT using multiple importance sampling to significantly reduce variance when rendering caustics reflected on highly glossy surfaces.


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