3DGS in short
NeRF (Neural Radiance Fields) forms images by sampling a neural field along many rays, which looks good but can be slow. 3D Gaussian Splatting (3DGS) replaces heavy per-pixel networks with many Gaussian splats and anisotropic points with color, opacity, and orientation. The renderer projects and blends them on screen, a point-based rendering style that maps well to GPUs and supports real-time novel view synthesis. Because splats remain differentiable, you can still optimize them with standard losses. If you need basics, see our overview.
Hybrid rendering model
HybridSplat is hybrid by design. The scene is split into two parts and rendered in one pipeline:
- Diffuse and background use standard splatting (point-based rendering with many Gaussian splats from 3D Gaussian Splatting (3DGS)).
- Specular and reflections use Gaussian Ray Tracing (ray–Gaussian intersection) to deliver view-dependent shading with proper parallax and specular highlights that plain SH-based 3DGS often misses.
This is not “just descriptors.” Reflections come from ray tracing, while most pixels still come from fast rasterized splats. That is the “hybrid” in HybridSplat, not a replacement of NeRF (Neural Radiance Fields) but a targeted fix for shiny materials.
Speed and benchmarks context
The page reports about 7× faster than earlier tracing-heavy splat methods on reflective sets, and fewer primitives after pruning. Note the nuance that HybridSplat is faster than prior ray-traced 3DGS baselines, but usually slower than vanilla 3DGS on purely diffuse scenes, because rays are still traced where reflections matter. The gain is the quality/speed balance for glossy content.
HybridSplat also uses tiled ray tracing. Rays and Gaussians are grouped by AABB tiles to improve L1/L2 cache use, not just a generic tile rasterizer. This is the “pipeline-level acceleration” the authors highlight.
Training signals and geometry
Upstream data stays familiar for AI and Computer vision pipelines:
- structure from motion (SfM) with COLMAP for camera pose estimation (pose estimation)
- geometry seeds from a point cloud or coarse mesh
- optional AI depth estimation (mono) or a stereo vision camera for better scale
For reflections to look correct, normals matter. Add normal estimation and a Normal Consistency Loss during differentiable rendering so reflective Gaussians align with the real surface. This helps the traced rays return stable answers frame to frame.
Source: HybridSplat
Renderer details that matter
HybridSplat’s draw path combines both branches:
- Tiled Gaussian grids with tight bounds
- Batched rasterization and persistent threads to keep SMs busy
- Memory arranged with GPU memory tiling (structure-of-arrays)
- Precision keep FP32 for ray/normal math; use mixed precision FP16 only where error won’t show up in highlights and edges
- Optional stability add-ons: multi-resolution splats, mipmapping for splats, light LOD heuristics for distant content
- Throughput aids caching strategies, streaming loaders, asynchronous transfer, and compute-graphics interop to hand results to a real-time renderer in Unity or Unreal Engine
Limits to keep in mind
Near-field specular reflections of very small or highly curved objects close to the camera remain difficult. You may see aliasing unless you increase sampling or add filtering, which will reduce FPS. The “4× fewer primitives” result depends on pruning settings, and pruning too aggressively can remove tiny mirror details. Precision is important for ray steps and normals, and relying too much on FP16 can cause shimmer.
Where it fits
HybridSplat drops into real projects that need real-time novel view synthesis with shiny materials:
- AR/VR, digital twins, 3D mapping, free-viewpoint video
- robotics and autonomous navigation that benefit from fast views for 3D perception, object tracking, multi-object tracking, and real time object detection
- R&D stacks built on Python computer vision with PyTorch (a quick PyTorch computer vision example can prototype the path), or Nerfstudio (Splatfacto) for baseline training before custom kernels
Why does this work for reflections
HybridSplat keeps diffuse parts fast with splatting and sends mirror-like regions to Gaussian Ray Tracing. That choice preserves view-dependent shading and correct parallax in reflections, rather than approximating them with low-order bases. Tiled ray tracing limits memory traffic, so you get realistic reflections without paying the full cost of tracing every pixel.
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