We propose a volumetric representation based on primitives to model scattering and emissive media. Accurate scene representations enabling efficient rendering are essential for many computer graphics applications. General and unified representations that can handle surface and volume-based representations simultaneously, allowing for physically accurate modeling, remain a research challenge. Inspired by recent methods for scene reconstruction that leverage mixtures of 3D Gaussians to model radiance fields, we formalize and generalize the modeling of scattering and emissive media using mixtures of simple kernel-based volumetric primitives. We introduce closed-form solutions for transmittance and free-flight distance sampling for 3D Gaussian kernels, and propose several optimizations to use our method efficiently within any off-the-shelf volumetric path tracer by leveraging ray tracing for efficiently querying the medium. We demonstrate our method as an alternative to other forms of volume modeling (e.g. voxel grid-based representations) for forward and inverse rendering of scattering media. Furthermore, we adapt our method to the problem of radiance field optimization and rendering, and demonstrate comparable performance to the state of the art, while providing additional flexibility in terms of performance and usability.

翻译：我们提出一种基于基元的体积表示方法，用于建模散射与发射介质。在许多计算机图形学应用中，能够实现高效渲染的精确场景表示至关重要。能够同时处理基于表面和体积的表示、并允许物理精确建模的通用统一表示方法，目前仍是一个研究挑战。受近期利用三维高斯混合来建模辐射场的场景重建方法启发，我们形式化并推广了使用基于简单核的体积基元混合来建模散射与发射介质的方法。我们针对三维高斯核引入了透射率和自由程采样的闭式解，并提出了若干优化策略，通过利用光线追踪高效查询介质，使我们的方法能够在任何现成的体积路径追踪器中高效使用。我们展示了本方法作为其他形式体积建模（例如基于体素网格的表示）的替代方案，用于散射介质的正向与逆向渲染。此外，我们将本方法应用于辐射场优化与渲染问题，并证明了其性能与当前最优方法相当，同时在性能与可用性方面提供了额外的灵活性。