WorldBridge: Bridging Indoor and Outdoor Spaces for Unified World Generation

Robots operating in the real world often need to complete continuous tasks across indoor and outdoor spaces, such as moving from a living room through a porch onto the street. However, existing methods typically treat indoor and outdoor scene generation as separate tasks, making it difficult to generate unified and spatially continuous open environments. This stems from two core challenges: (1) Continuous indoor-outdoor scene data is scarce, so reliable joint generation priors are hard to obtain; (2) Indoor layouts and outdoor connections need to be coordinated, while post-hoc stitching often yields unnatural transitions. To address these challenges, we propose WorldBridge, a procedural framework that bridges indoor and outdoor spaces to generate the unified open world. WorldBridge consists of three stages. First, Spatial Contract Coordination derives domain-specific contracts for indoor spaces, building envelopes, and outdoor environments, and reconciles them into a shared spatial contract. Second, Contract-Conditioned 3D World Realization jointly generates scene structure and assets under the shared spatial contract, producing a coherent 3D world. Finally, Physics-Aware Dynamic Extension attaches object and environmental dynamics to the structured scene, yielding an executable 4D world. Experiments demonstrate that WorldBridge reliably generates diverse, visually compelling, and spatially coherent indoor–outdoor worlds. Project page: https://anonymous.4open.science/w/worldbridge-4F42/.