Research map / 3D vision / Gaussian splatting
IRGS: Inter-Reflective Gaussian Splatting with 2D Gaussian Ray Tracing
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Proposes IRGS, an inverse rendering framework that applies the full rendering equation to 2D Gaussian splatting using a differentiable 2D Gaussian ray tracer to compute visibility and indirect radiance on the fly.
Problem
Inverse rendering with Gaussian splatting usually simplifies the rendering equation or uses learnable parameters for incident light, which fails to capture inter-reflection and yields inaccurate material and lighting estimates.
Approach
Ray tracing directly over 2D Gaussian primitives (with well-defined ray-splat intersections) lets a pretrained 2DGS model be used as a differentiable ray tracer, so the full rendering equation with Monte Carlo sampling and indirect light can be evaluated and optimized, plus a split-sum-based indirect query for relighting.
Key results
- On TensoIR, IRGS reaches 33.80 albedo PSNR and 29.91 relighting PSNR, outperforming baselines on relighting and albedo.
- On Synthetic4Relight, IRGS achieves 34.90 relighting PSNR and 0.7 hours training time, versus 0.9 hours for R3DG.
- 2D Gaussian ray tracing on a pretrained 2DGS checkpoint gives PSNR 34.06 versus 26.90 for 3D Gaussian ray tracing on a 3DGS checkpoint.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use IRGS instead of R3DG | inverse rendering on Synthetic4Relight · Synthetic4Relight | Relighting PSNR: 31.00 -> 34.90 | Helped |
| use IRGS instead of R3DG | inverse rendering on Synthetic4Relight · Synthetic4Relight | NVS PSNR: 36.80 -> 35.48 | Hurt |
| use IRGS instead of R3DG | inverse rendering on TensoIR · TensoIR | Relighting PSNR: 27.367 -> 29.907 | Helped |
| use IRGS instead of R3DG | inverse rendering on TensoIR · TensoIR | NVS PSNR: 37.343 -> 35.876 | Hurt |
| add indirect-light gradients through ray tracing (ablation) | IRGS · Synthetic4Relight (four-scene average) | Relighting PSNR: 34.22 -> 34.68 | Helped |
| include indirect light during training (ablation) | IRGS · Synthetic4Relight (four-scene average) | Albedo PSNR: 30.10 -> 30.81 | Helped |
| include indirect light during training (ablation) | IRGS · Synthetic4Relight (four-scene average) | Relighting PSNR: 33.93 -> 34.68 | Helped |
| query indirect radiance during relighting (ablation) | IRGS · Synthetic4Relight (four-scene average) | Relighting PSNR: 33.84 -> 34.68 | Helped |
| increase sampled rays from Nr = 16 to Nr = 256 (ablation) | IRGS · Synthetic4Relight (four-scene average) | Relighting PSNR: 29.46 -> 34.68 | Helped |
| increase sampled rays from Nr = 64 to Nr = 256 (ablation) | IRGS · Synthetic4Relight (four-scene average) | NVS PSNR: 34.98 -> 35.48 | Helped |
Surprising findings
- Directly applying 3D Gaussian ray tracing to a pretrained 3DGS checkpoint drops PSNR from 38.59 to 26.90, while 2D Gaussian ray tracing loses much less (37.55 to 34.06).
Limitations
- High computational cost of rendering equation evaluation prevents high frame-rate rendering
- Rendering is slow (about 1 second per image)
Experimental setup
Datasets: Synthetic4Relight TensoIR Stanford-ORB
Benchmarks: Synthetic4Relight TensoIR Stanford-ORB
Metrics: PSNR SSIM LPIPS MAE MSE
Baselines: NeRFactor InvRender TensoIR GS-IR R3DG
Builds on: 2D Gaussian splatting 3DGRT R3DG GS-IR Nvdiffrec
Closest papers by meaning
- GaussianShader: 3D Gaussian Splatting with Shading Functions for Reflective Surfaces (CVPR 2024 · similarity 0.92)
- Reflective Gaussian Splatting (ICLR 2025 · similarity 0.90)
- Ref-GS: Directional Factorization for 2D Gaussian Splatting (CVPR 2025 · similarity 0.89)
- Subsurface Scattering for Gaussian Splatting (NeurIPS 2024 · similarity 0.87)
- Hardware-Rasterized Ray-Based Gaussian Splatting (CVPR 2025 · similarity 0.87)
- Gaussian Splashing: Unified Particles for Versatile Motion Synthesis and Rendering (CVPR 2025 · similarity 0.87)
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