Multiple Scattering in Inhomogeneous Participating Media Using Rao‐Blackwellization and Control Variates
Multiple Scattering in Inhomogeneous Participating Media Using Rao‐Blackwellization and Control Variates
复制标题
使用 Rao-Blackwell 化和控制变量在非均匀参与介质中进行多重散射
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
M. Sbert
中科院分区：
文献类型：
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作者：
László Szirmay;M. Magdics;M. Sbert
渲染不均匀的参与介质需要大量的体积样本，因为消光系数需要沿沿着光路积分。光线行进使小步，这是耗时的，并导致有偏见的算法。Woodcocklike方法使用分析抽样和随机拒绝方案，保证期望值与原始模型相同。这些模型和消光控制变量的应用已经成功地计算透射率和单次散射，但没有充分利用在多次散射模拟。我们的论文攻击在非均匀介质中的多次散射问题，并修改光-介质相互作用模型，允许使用简单的解析公式，同时保持正确的期望值。模型转换在Rao-Blackwellization的帮助下降低了估计值的方差，并将控制变量应用于消光系数和入射辐射率。基于变换后的模型，得到了高效的蒙特卡罗绘制算法。
Rendering inhomogeneous participating media requires a lot of volume samples since the extinction coefficient needs to be integrated along light paths. Ray marching makes small steps, which is time consuming and leads to biased algorithms. Woodcocklike approaches use analytic sampling and a random rejection scheme guaranteeing that the expectations will be the same as in the original model. These models and the application of control variates for the extinction have been successful to compute transmittance and single scattering but were not fully exploited in multiple scattering simulation. Our paper attacks the multiple scattering problem in heterogeneous media and modifies the light–medium interaction model to allow the use of simple analytic formulae while preserving the correct expected values. The model transformation reduces the variance of the estimates with the help of Rao‐Blackwellization and control variates applied both for the extinction coefficient and the incident radiance. Based on the transformed model, efficient Monte Carlo rendering algorithms are obtained.