Ray tracing enables 3D Gaussian fields to serve as a representation for physically based light transport. Faithful inverse rendering requires forward rendering and backward optimization to be defined within a consistent light-transport pipeline. Existing inverse rendering methods estimate G-buffers via splatting and optimize materials in screen space, tying the recovered properties to a rasterization-based pipeline. This pipeline mismatch, together with simplified rendering equations that neglect indirect illumination, often leads to inconsistent shading, visible artifacts, and inaccurate material-lighting estimation under path-traced rendering. Therefore, we propose a splatting-free path-traced inverse rendering framework for 3D Gaussian fields, where forward light transport and backward gradient propagation are defined within a unified ray-tracing pipeline. Our key idea is to define a path-space equivalent interaction model for overlapping Gaussian primitives, under which Monte-Carlo-based path tracing is unbiased for the induced light-transport integral, while pathwise gradients are replayed over the same ray-traced interactions rather than splatting-derived screen-space buffers. The framework optimizes materials and a compact Spherical-Gaussian environment under the full rendering equation with ray-traced visibility and multi-bounce light transport. Extensive experiments demonstrate competitive material inversion and improved path-traced rendering quality, producing more plausible shadows, reflections, and relighting results under global illumination.

翻译：光线追踪使得3D高斯场能够作为基于物理的光传输表示。对忠实逆渲染而言，前向渲染和反向优化需在一致的光传输流水线中定义。现有逆渲染方法通过抛雪球法估计G缓冲区并在屏幕空间优化材质，将恢复的属性与栅格化流水线绑定。这种流水线不匹配，加之忽略间接照明的简化渲染方程，常导致路径追踪渲染下着色不一致、可见伪影以及材质-光照估计不准确。为此，我们提出一种无抛雪球法的3D高斯场路径追踪逆渲染框架，其中前向光传输和反向梯度传播在统一的光线追踪流水线中定义。核心思想是为重叠高斯基元定义路径空间等效交互模型，使得基于蒙特卡洛的路径追踪对推导的光传输积分无偏，同时路径梯度在相同光线追踪交互上回放，而非基于抛雪球法导出的屏幕空间缓冲区。该框架在含光线追踪可见性和多反弹光传输的完整渲染方程下优化材质和紧凑球面高斯环境。大量实验证明该方法在材质反演和路径追踪渲染质量上具有竞争力，能在全局光照下产生更逼真的阴影、反射和重照明结果。