An Interactive LLM-Based Framework for Spatial Relationship Query on Openbim Elements with Ifc4 Schema

Spatial relationships between BIM elements are crucial for various BIM-based analysis (e.g., identifying external building envelope components for energy simulation), however current BIM information retrieval researches are mainly in the field of extracting attributes from BIM element, a solution for obtaining implicit spatial information from BIM model is needed. Thus, this research focus on how to accurately and effectively obtaining spatial relationship between BIM elements and reliable answering spatial-related BIM query. Addressing this issue, we proposed a IFC-based spatial relation calculation and query-answer framework, which is summarized as follows: (1) extract geometric information of the IFC entities with openBIM standards and obtain the triangulated boundary data of each entities; (2) generate AABB tree of the entities using triangulated boundary data to index the entities and improve the search efficiency in spatial calculation; (3) bSDD-aided LLM workflow to align natural-language queries with corresponding IFC entities to answer spatial relationship queries. We use several building cases to verify our proposed method, the results indicate that our method can accurately understand the natural language query (92.1% correct rate on query understanding tasks) and efficiently determine elements’ spatial relationship (saving 61.4% average query time) to answer the original query. With our query method, users with minimal BIM experience (e.g., construction site workers) can still easily query the spatial relationship in a user-friendly way, improving the applicability of the BIM technique.