A Local Frequency Analysis of Light Scattering and Absorption
A Local Frequency Analysis of Light Scattering and Absorption
复制标题
光散射和吸收的局部频率分析
DOI：
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发表时间：
2014
影响因子：
6.2
通讯作者：
C. Soler
中科院分区：
文献类型：
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作者：
Laurent Belcour;Kavita Bala;C. Soler
渲染参与的媒体需要大量的计算，但体积散射的效果最终通常是平滑的。提出了一种在傅里叶域内分析局部光场吸收和散射的新方法，并推导了相应的光场功率谱协方差矩阵上的算子集。这种分析为光在参与介质中沿光路的行为提供了一种有效的预测工具。我们利用这一分析，通过组合体积中的每个光路信息，在3D中得出适当的频率预测度量。我们演示了使用这些度量来显著改进用于模拟参与介质中的多重散射的各种现有方法的收敛。首先，我们提出了一种高效的通量二阶导数的计算方法，用于辐照度缓存等方法。其次，我们推导了图像空间自适应采样和重建的合适的滤波器和自适应样本密度。第三，我们提出了一种自适应采样的方法来整合摄像机的散射光照。最后，我们通过预测聚光半径在哪里可以停止减小来改善渐进光子光束的会聚。参与介质中的光路可能非常复杂。我们的主要贡献在于，分析傅立叶域中的局部光场揭示了此类介质中光照的一致性，并提供了一套简单而有用的规则用于加速现有的全局照明方法。
Rendering participating media requires significant computation, but the effect of volumetric scattering is often eventually smooth. This article proposes an innovative analysis of absorption and scattering of local light fields in the Fourier domain and derives the corresponding set of operators on the covariance matrix of the power spectrum of the light field. This analysis brings an efficient prediction tool for the behavior of light along a light path in participating media. We leverage this analysis to derive proper frequency prediction metrics in 3D by combining per-light path information in the volume. We demonstrate the use of these metrics to significantly improve the convergence of a variety of existing methods for the simulation of multiple scattering in participating media. First, we propose an efficient computation of second derivatives of the fluence, to be used in methods like irradiance caching. Second, we derive proper filters and adaptive sample densities for image-space adaptive sampling and reconstruction. Third, we propose an adaptive sampling for the integration of scattered illumination to the camera. Finally, we improve the convergence of progressive photon beams by predicting where the radius of light gathering can stop decreasing. Light paths in participating media can be very complex. Our key contribution is to show that analyzing local light fields in the Fourier domain reveals the consistency of illumination in such media and provides a set of simple and useful rules to be used to accelerate existing global illumination methods.