GridFlow: Structured Latent Flow for Seamless City-Scale 3D Point Cloud Generation

arXiv:2608.29793v1 Announce Type: new Abstract: Generating realistic 3D city environments from remote sensing data is important for simulation, urban planning, and mixed reality, yet existing point cloud generation methods are limited to single objects or bounded indoor scenes and cannot handle the scale, seamless tiling, and partial observability challenges of city-scale generation. We present ours{}, a multi-stage framework that generates dense, colored point clouds (10^5 points per 150ext{m}{imes}150ext{m} tile) at city scale, conditioned on satellite imagery, semantic segmentation maps, and digital surface models (DSM). A Grid-Aligned VAE encodes each tile into a topology-preserving latent grid where tokens correspond to fixed spatial regions, enabling spatially coherent multi-modal conditioning and compact latent-space edge consistency that implicitly aligns thousands of boundary points for seamless cross-tile generation. A conditional rectified flow model synthesizes geometry latents from the fused multi-modal conditions, and an orientation-aware diffusion colorizer separately handles satellite-visible horizontal surfaces and occluded vertical facades. To support standardized evaluation, we build on public 3D data sources to introduce City3D-MultiGen, a benchmark of 163K densely annotated tiles from Melbourne and London with aligned point clouds, satellite images, semantic maps, and elevation data. Experiments show that ours{} outperforms adapted point cloud generation baselines across all geometry metrics and produces visually coherent colored point clouds with seamless boundaries over arbitrarily large urban extents. Our benchmark details are available at https://huggingface.co/datasets/e32/City3D-MultiGen

Source: arXiv cs.CV | 2026-09-01

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