UrbanBP-GS: Building-Aware Partitioning and Planarity-Constrained Updating for Morphology-Adaptive Urban Novel-View Synthesis

Block-wise reconstruction based on 2D Gaussian Splatting (2DGS) has emerged as a promising paradigm for high-fidelity novel-view synthesis of large urban scenes. However, this paradigm encounters bottlenecks in scene partitioning and primitive representation. Partitioning schemes suffer from inter-block primitive imbalance and building fragmentation, while 2DGS limits the rendering of geometrically irregular structures. To address these limitations, we propose UrbanBP-GS, a morphology-adaptive framework that uses building-aware scene partitioning to balance primitive counts and preserve building connectivity, and planarity-constrained 3D Gaussian updating to support high-fidelity urban rendering with irregularity-tolerant primitives. For building-aware scene partitioning, UrbanBP-GS first initializes scene partitioning under a primitive-balance constraint, then detects connected buildings spanning multiple blocks and consolidates each building into its dominant block under a per-block primitive-count variation budget. For planarity-constrained 3D Gaussian updating, UrbanBP-GS associates each planar region with its contributing Gaussians, estimates their normals through soft shortest-axis selection, and promotes orientation consistency among Gaussians in the same planar region while preserving nonzero-thickness primitives to represent irregular structures. Extensive experiments demonstrate that UrbanBP-GS achieves superior PSNR and LPIPS performance across multiple large-scale urban scenes, with particularly notable gains in densely built areas.