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.

中文翻译：

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参与媒体的实用路径引导方法

渲染半透明材料的成本很高：光传输算法需要在达到收敛之前模拟材料内部的大量散射事件。对于反照率较大或平均自由程较小的材料，其成本特别高，在这些材料中，高阶散射效应占主导地位。简单来说，路径在介质中迷路了。已经提出了用于表面渲染的路径引导，以通过引导采样过程来加快收敛速度​​。在本文中，我们介绍了半透明材料的路径引导解决方案。我们学习了体积中辐射分布的自适应近似表示，并使用它来采样散射方向，并通过重采样的重要性采样将其与相位函数采样相结合。所提出的方法大大提高了参与介质中光传输模拟的性能，尤其是对于小光和具有折射边界的介质。我们的方法可以处理任何均质的参与介质，具有高或低散射，高或低吸收以及从各向同性到高度各向异性。