Path-Traced Inverse Rendering with Global Illumination in 3D Gaussian Fields

Researchers from multiple institutions have proposed a splatting-free inverse rendering framework for 3D Gaussian fields that grounds both forward rendering and backward optimization within a unified ray-tracing pipeline. The approach addresses a longstanding mismatch in existing methods, which estimate geometry buffers via rasterization-based splatting and then optimize materials in screen space — a disconnect that produces inconsistent shading, visible artifacts, and inaccurate material-lighting decomposition when the final render is path-traced.

The key contribution is a path-space interaction model for overlapping Gaussian primitives that makes Monte Carlo path tracing unbiased for the induced light-transport integral, while allowing pathwise gradients to be replayed over ray-traced interactions rather than screen-space buffers. The framework jointly optimizes surface materials and a compact Spherical-Gaussian environment representation under the full rendering equation, incorporating ray-traced visibility and multi-bounce light transport. Experiments show competitive material inversion and improved rendering quality, with more plausible shadows, reflections, and relighting under global illumination.