Existing fiber scattering models in rendering are all based on tracing rays through fiber geometry, but for small fibers diffraction and interference are non-negligible, so relying on ray optics can result in appearance errors. This paper presents the first wave optics based fiber scattering model, introducing an azimuthal scattering function that comes from a full wave simulation. Solving Maxwell's equations for a straight fiber of constant cross section illuminated by a plane wave reduces to solving for a 3D electromagnetic field in a 2D domain, and our fiber scattering simulator solves this 2.5D problem efficiently using the boundary element method (BEM). From the resulting fields we compute extinction, absorption, and far-field scattering distributions, which we use to simulate shadowing and scattering by fibers in a path tracer. We validate our path tracer against the wave simulation and the simulation against a measurement of diffraction from a single textile fiber. Our results show that our approach can reproduce a wide range of fibers with different sizes, cross sections, and material properties, including textile fibers, animal fur, and human hair. The renderings include color effects, softening of sharp features, and strong forward scattering that are not predicted by traditional ray-based models, though the two approaches produce similar appearance for complex fiber assemblies under many conditions.

中文翻译：

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基于波动光学的光纤散射模型

现有的渲染中的光纤散射模型都是基于通过光纤几何形状追踪光线，但对于小光纤来说，衍射和干涉是不可忽略的，因此依赖射线光学会导致外观错误。本文介绍了第一个基于波光学的光纤散射模型，介绍了来自全波模拟的方位角散射函数。求解由平面波照射的恒定截面直光纤的麦克斯韦方程可简化为求解 2D 域中的 3D 电磁场，我们的光纤散射模拟器使用边界元法 (BEM) 有效地解决了这个 2.5D 问题。从得到的场中，我们计算消光、吸收和远场散射分布，我们用它们来模拟路径跟踪器中的纤维的阴影和散射。我们针对波模拟验证了我们的路径示踪剂，并针对单根纺织纤维的衍射测量进行了模拟。我们的结果表明，我们的方法可以复制具有不同尺寸、横截面和材料特性的各种纤维，包括纺织纤维、动物毛皮和人类头发。渲染包括颜色效果、锐化特征的软化和传统基于射线的模型无法预测的强前向散射，尽管这两种方法在许多条件下为复杂的纤维组件产生相似的外观。包括纺织纤维、动物毛皮和人发。渲染包括传统基于射线的模型无法预测的颜色效果、锐化特征的软化和强前向散射，尽管这两种方法在许多条件下为复杂的纤维组件产生相似的外观。包括纺织纤维、动物毛皮和人发。渲染包括颜色效果、锐化特征的软化和传统基于射线的模型无法预测的强前向散射，尽管这两种方法在许多条件下为复杂的纤维组件产生相似的外观。