Towards practical physical-optics rendering
Towards practical physical-optics rendering
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DOI：
10.1145/3528223.3530119
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发表时间：
2022-07
期刊：
影响因子：
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通讯作者：
Shlomi Steinberg;P. Sen;Ling-Qi Yan
中科院分区：
文献类型：
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作者：
Shlomi Steinberg;P. Sen;Ling-Qi Yan
物理光输运（PLT）算法能够全面表征场景中光的波动性质，与麦克斯韦电磁学理论相一致。因此，它们能够再现真实物理光学的波干涉和衍射效应。然而，最近提出PLT的作品过于昂贵，无法应用于具有复杂几何形状和材料的现实场景。为了解决这个问题，我们提出了一个新的物理光传输框架，该框架基于几个关键思想，实际上使PLT适用于复杂场景。首先，我们将光的空间相干形状限制为各向异性高斯形状，并用基于熵的一般参数来证明这一限制。这一限制有助于简化其余的推导，而不会丧失实际的通用性。为了描述部分相干光，我们提出了新的渲染基元，这些基元基于众所周知的Stokes参数，概括了辐射亮度和辐照度。我们能够表示任意光谱含量和偏振状态的光，并且具有任何相干体积和各向异性。我们还提出了波的BSDF，以准确地呈现衍射和波的干涉效应。此外，我们提出了一种对该波BSDF进行重要采样的方法，以促进双向路径跟踪，这在以前是不可能的。我们与最先进的方法表现出良好的一致性，但与他们不同的是，我们能够渲染复杂的场景，其中所有的材料都是新的，相干感知物理光学材料，并且性能接近“经典”渲染方法。
Physical light transport (PLT) algorithms can represent the wave nature of light globally in a scene, and are consistent with Maxwell's theory of electromagnetism. As such, they are able to reproduce the wave-interference and diffraction effects of real physical optics. However, the recent works that have proposed PLT are too expensive to apply to real-world scenes with complex geometry and materials. To address this problem, we propose a novel framework for physical light transport based on several key ideas that actually makes PLT practical for complex scenes. First, we restrict the spatial coherence shape of light to an anisotropic Gaussian and justify this restriction with general arguments based on entropy. This restriction serves to simplify the rest of the derivations, without practical loss of generality. To describe partially-coherent light, we present new rendering primitives that generalize the radiometric radiance and irradiance, and are based on the well-known Stokes parameters. We are able to represent light of arbitrary spectral content and states of polarization, and with any coherence volume and anisotropy. We also present the wave BSDF to accurately render diffractions and wave-interference effects. Furthermore, we present an approach to importance sample this wave BSDF to facilitate bi-directional path tracing, which has been previously impossible. We show good agreement with state-of-the-art methods, but unlike them we are able to render complex scenes where all the materials are new, coherence-aware physical optics materials, and with performance approaching that of "classical" rendering methods.