Research map / 3D vision / Gaussian splatting
Dynamic 3D Gaussian Fields for Urban Areas
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Proposes 4DGF, a hybrid scene representation combining 3D Gaussians as a geometry scaffold, hash-grid neural fields for appearance and transient geometry, and a scene graph with deformations for dynamic objects, enabling large-scale heterogeneous urban NVS at interactive rates.
Problem
Novel-view synthesis of large-scale, dynamic urban areas from heterogeneous captures (varying weather, season, lighting) at interactive rendering speeds, which prior NeRF and 3DGS methods cannot handle.
Approach
Use 3D Gaussians without per-primitive appearance as a geometry scaffold, with hash-grid neural fields predicting per-sequence color and opacity attenuation (transient geometry), a scene graph of sequence/object nodes for global rigid motion, and canonical-space deformations for non-rigid objects, plus multi-GPU ADC and pose optimization.
Key results
- On Argoverse 2 multi-sequence NVS, 4DGF reaches 24.97 mean PSNR versus 21.15 for ML-NSG (over 3 dB better) with 0.074 s render time versus 21.7 s.
- On KITTI [75%], 4DGF achieves 31.34 PSNR and 0.945 SSIM, outperforming StreetGaussians (25.79 PSNR).
- On Waymo Dynamic-32, 4DGF reaches 29.04 full-image PSNR and 29.34 dynamic-only PSNR, with 0.025 s rendering, about 700x faster than the best alternative.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use 4DGF instead of ML-NSG | Argoverse 2 Residential + Downtown (Mean) · Argoverse 2 | PSNR: 21.15 -> 24.97 | Helped |
| Use 4DGF instead of ML-NSG | Argoverse 2 Residential + Downtown (Mean) · Argoverse 2 | render time: 21.7 -> 0.074 | Helped |
| Use dynamic modeling (ablation) | 4DGF, single-sequence · Residential split | PSNR: 24.31 -> 28.55 | Helped |
| Use neural fields instead of per-Gaussian appearance attributes (ablation) | 4DGF, single-sequence · Residential split | GPU memory: 8.6 GB -> 4.5 GB | Helped |
| Add the generated 3D Gaussian background (ablation) | 4DGF, single-sequence · Residential split | PSNR: 28.49 -> 28.81 | Helped |
| Add sequence appearance modeling (ablation) | 4DGF, multi-sequence · Residential split | PSNR: 22.37 -> 25.13 | Helped |
| Add transient-geometry modeling (ablation) | 4DGF, multi-sequence · Residential split | PSNR: 25.13 -> 25.78 | Helped |
| Add deformation head χ for non-rigid motion (ablation) | 4DGF · Waymo Open Dynamic-32 subset (12 sequences with most non-rigid objects), Full Image | PSNR: 29.52 -> 29.60 | Helped |
| Use modified ADC instead of vanilla ADC (ablation) | 4DGF · Residential split, single-sequence | PSNR: 28.60 -> 28.81 | Helped |
| Use predicted rather than ground-truth 3D boxes (ablation) | 4DGF · Residential split, single-sequence | PSNR: 28.81 -> 28.52 | Hurt |
| Use predicted rather than ground-truth 3D boxes (ablation) | 4DGF · Residential split, multi-sequence | PSNR: 25.78 -> 25.67 | Hurt |
| Add regularization on 3D Gaussian scales (ablation) | 4DGF · Urban scene reconstruction | view synthesis metrics | No clear effect |
Surprising findings
- Modeling per-Gaussian appearance with neural fields is on par with spherical harmonics in quality while halving peak training GPU memory (8.6 GB to 4.5 GB).
- Neural field queries account for only 13.3% of average runtime, with scene graph evaluation and rasterization dominating.
Limitations
- Assumes a pinhole camera model and does not handle distortions such as rolling shutter, white balance, or blur.
- Does not model other sensors such as LiDAR or non-pinhole cameras like equirectangular.
- Large Gaussians can cause fog-like artifacts in free-viewpoint renderings.
Experimental setup
Datasets: Argoverse 2 KITTI VKITTI2 Waymo Open
Benchmarks: Argoverse 2 NVS benchmark KITTI VKITTI2 Waymo Open Dynamic-32
Metrics: PSNR SSIM LPIPS render time
Baselines: SUDS ML-NSG Nerfacto NSG MARS StreetGaussians EmerNeRF NeuRAD
Builds on: 3D Gaussian splatting Neural Scene Graphs Instant-NGP EmerNeRF SUDS
Closest papers by meaning
- Multi-Level Neural Scene Graphs for Dynamic Urban Environments (CVPR 2024 · similarity 0.91)
- 4D3R: Motion-Aware Neural Reconstruction and Rendering of Dynamic Scenes from Monocular Videos (NeurIPS 2025 · similarity 0.88)
- DynamicCity: Large-Scale 4D Occupancy Generation from Dynamic Scenes (ICLR 2025 · similarity 0.88)
- Deformable 3D Gaussians for High-Fidelity Monocular Dynamic Scene Reconstruction (CVPR 2024 · similarity 0.88)
- Real-time Photorealistic Dynamic Scene Representation and Rendering with 4D Gaussian Splatting (ICLR 2024 · similarity 0.87)
- Swift-Mapping: Online Neural Implicit Dense Mapping in Urban Scenes (AAAI 2024 · similarity 0.87)
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