RAGA: Real Time Ray Traced Gaussian Shadow Casting for 3DGS Avatar-Scene Interaction

We study the problem of physically plausible shadow castingwhen animating 3D Gaussian Splatting (3DGS) avatars, either individu-ally or in multi-avatar and object-interaction scenarios, within existing3DGS scenes. In contrast to prior methods that rely on binary hit tests andmesh-based shadow casters, our method performs shadow computationentirely in Gaussian space, without requiring any mesh reconstruction. Weintroduce RAGA, a Ray-Traced Gaussian Shadow Casting formulationbased on exact ray–Gaussian line integrals. For each occluding Gaussian,we integrate the opacity profile along the shadow ray and normalize bythe theoretical maximum integral, producing a weight that captures howthe ray traverses the occluder rather than merely whether an intersectionoccurred. To reduce temporal variance from clothing deformations in ani-mated avatars, we further introduce an avatar proxy representation thatstabilizes shadow casting while preserving visual fidelity. We implement*Work partly done as intern at Snap Inc.RAGA using custom CUDA kernels integrated with the NVIDIA OptiXframework; as such, our shadow tracer runs at rates of about 50 FPS.We evaluate on single-avatar, multi-avatar, and avatar–object interactionscenarios across multiple datasets, demonstrating substantially improvedshadow realism, temporal stability, and scene coherence. Our project pageis available at https://miraymen.github.io/raga/.