GRay: Ray Tracing 3D Gaussians Near the Speed of Splats

Abstract

3D Gaussian Splatting (3DGS) is a popular representation for radiance field reconstruction, distinguished by the rendering speed of its rasterization-based renderer. While 3D Gaussians can also be ray traced, this approach has so far been slower, with 3D Gaussian Ray Tracing (3DGRT) taking nearly one order of magnitude longer to optimize. To address this, we present GRay, a fast ray tracer for 3D Gaussians designed to close this performance gap and match 3DGS's speed. Our method leverages the algorithmic difference between both approaches: unlike rasterization, ray tracing evaluates only Gaussians that are actually intersected by a ray, leading to potentially logarithmic--rather than linear--scaling in the number of primitives. This property allows ray tracing to better exploit dense scenes composed of numerous tiny Gaussians, a configuration which has largely been overlooked. Notably, we show that dense initialization--which creates many small Gaussians--slows down rasterization, but instead speeds up ray tracing. Designed to leverage this effect, GRay renders nearly 4x faster and optimizes nearly 10x faster than 3DGRT while maintaining similar quality, and has competitive speed with 3DGS albeit at somewhat lower quality. Code is available at https://repo-sam.inria.fr/nerphys/gray.

12 pages plus supplementary material, 33 pages total; Proceedings of the ACM on Computer Graphics and Interactive Techniques, I3D 2026

References in corpus (6)

• RoMa: Robust Dense Feature Matching
• Comparison of Image Quality Models for Optimization of Image Processing Systems
• Reducing the Memory Footprint of 3D Gaussian Splatting
• AdR-Gaussian: Accelerating Gaussian Splatting with Adaptive Radius
• Don't Splat your Gaussians: Volumetric Ray-Traced Primitives for Modeling and Rendering Scattering and Emissive Media
• Editable Physically-based Reflections in Raytraced Gaussian Radiance Fields