Rendering volumetric scattering media, including clouds, fog, smoke, and other complex materials, is crucial for realism in computer graphics. Traditional path tracing, while unbiased, requires many long path samples to converge in scenes with scattering media, and a lot of work is wasted by paths that make a negligible contribution to the image. Methods to make better use of the information learned during path tracing range from photon mapping to radiance caching, but struggle to support the full range of heterogeneous scattering media. This paper introduces a new volumetric rendering algorithm that extends and adapts the previous \emph{path graph} surface rendering algorithm. Our method leverages the information collected through multiple-scattering transport paths to compute lower-noise estimates, increasing computational efficiency by reducing the required sample count. Our key contributions include an extended path graph for participating media and new aggregation and propagation operators for efficient path reuse in volumes. Compared to previous methods, our approach significantly boosts convergence in scenes with challenging volumetric light transport, including heterogeneous media with high scattering albedos and dense, forward-scattering translucent materials, under complex lighting conditions.

中文翻译：

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使用路径图渲染参与媒体

渲染体积散射介质（包括云、雾、烟和其他复杂材质）对于计算机图形的真实感至关重要。传统的路径追踪虽然无偏差，但需要许多长路径样本在具有散射介质的场景中收敛，并且对图像的贡献可以忽略不计的路径浪费了大量工作。更好地利用路径跟踪过程中学到的信息的方法包括从光子映射到辐射缓存，但很难支持全系列的异构散射介质。本文介绍了一种新的体积渲染算法，该算法扩展并适应了之前的 \emph{path graph} 表面渲染算法。我们的方法利用通过多个​​散射传输路径收集的信息来计算较低噪声的估计，通过减少所需的样本数量来提高计算效率。我们的主要贡献包括参与媒体的扩展路径图以及新的聚合和传播运算符，以实现批量有效的路径重用。与以前的方法相比，我们的方法显着提高了具有挑战性的体积光传输场景的收敛性，包括在复杂的照明条件下具有高散射反照率的异构介质和致密的前向散射半透明材料。