ShellMaker: Language-Guided Exterior Completion under Structural Constraints

Despite advances in indoor scene generation, synthesizingcoherent building exteriors consistent with generated interiors remainslargely unexplored. Existing methods can generate floor plans and walllayouts but typically stop at a structural shell, lacking stylistically con-sistent facades and roofs. Completing these exteriors is challenging be-cause the footprint, wall geometry, and opening semantics must remainfixed—constraints that unconstrained generative models often violate.We introduce ShellMaker, a language-guided exterior completion frame-work that operates under these structural constraints. Given a build-ing scaffold and a text style prompt, ShellMaker generates a completeexterior mesh with PBR materials by combining parametric roof gen-eration, LLM-based part-aware prompt refinement, joint wall–roof ma-terial retrieval, and geometry-aware assembly. Operating on a format-agnostic scaffold representation, ShellMaker generalizes to indoor gener-ators, CityGML, and CAD inputs, while maintaining structural consis-tency and improving architectural coherence over retrieval and uncon-strained generative baselines. The project page is available at https://ruiqixu37.github.io/ShellMaker_web/.