Failing to Reflect Reality: Gaussian Splatting’s Collapse on Non-Lambertian Surfaces

We explore the applicability of Gaussian Splatting (GS) to the view synthesis (VS) of non-Lambertian objects. Materials with anisotropic appearance have always been a failure case for VS, until the recent introduction of spherical harmonics promising satisfying results to handle view-directional aspects. Nevertheless, we demonstrate that highly non-Lambertian objects, such as glass or mirrors, remain impossible to correctly reconstruct and render with Gaussian primitives and spherical harmonics. This paper clarifies the reasons: (1) Gaussian Splatting optimization converges to incorrect geometry, and (2) spherical harmonics fail to represent consistent view dependencies. Benchmarking experiments confirm that gs produces false geometry even with ground truth data. Our findings call into question current material representations in view synthesis and motivate the use of more realistic primitives.