CityGaussian: Real-time high-quality large-scale scene rendering with Gaussians

Original Article ↗ Hacker News Discussion ↗

Performance, “Real-Time,” and Hardware

  • Reported 36 FPS on an A100 leads to debate over what “real-time” means; several note the traditional graphics-paper pattern of using modest resolutions and very high-end GPUs.
  • Some argue A100-level performance will trickle down to consumer GPUs in a few years; others note deliberate market segmentation between “pro” and “consumer” lines.
  • There’s discussion about whether memory bandwidth (A100) or raw compute (e.g., 4090) is the bottleneck; unclear from the thread.
  • Multiple commenters cite other Gaussian splatting implementations already achieving 60–400+ FPS on consumer hardware or in browsers, though performance is highly device-dependent.

Scaling, LOD, and Optimization

  • CityGaussian is praised as one of the first 3D Gaussian Splatting methods to use LOD and spatial blocking for large-scale scenes.
  • Many believe there is substantial room for optimization (LOD streaming, pruning, formats, compression), and that research code tends to be far from production-quality.

Use Cases: Maps, Games, VR, and “3D Photos”

  • Strong interest in applications to Google Maps/Earth–style city exploration and virtual production, but skepticism about mobile viability in the short term.
  • For games, key challenge is dynamics: current methods are mostly static with baked lighting. Efficient animation, object interaction, and consistent lighting in hybrid pipelines remain open problems.
  • Some see 3DGS as ideal for “3D photographs” and static environments (VR, virtual sets), with hybrid pipelines mixing splats and traditional meshes.

Comparison to Photogrammetry and Meshes

  • Proponents say 3DGS outperforms classical photogrammetry on complex, semi-volumetric, or fine-detail content (foliage, hair, rough surfaces).
  • Skeptics argue 3DGS is data-heavy, slow, blurry up close, and poorly suited to non-Lambertian materials due to underlying Structure-from-Motion limitations.
  • Several suggest 3DGS may be better as an output/final-render format, with meshes still useful for editing and animation; others point to active work on converting between meshes and splats.

Data, Demos, and Related Work

  • The showcased city dataset (MatrixCity) is identified as derived from Unreal Engine’s Matrix city, i.e., synthetic but photorealistic, with perfect camera poses.
  • Commenters link related large-scale GS work (e.g., octree-based methods) and simple web demos mixing Google 3D tiles with splats.

Miscellaneous

  • Interest in open-source licensing and engines.
  • Brief off-topic subthread discusses how motion blur is implemented via motion vectors and post-processing in games.