Constructive solid geometry for automatic topology-aware BIM reconstruction from point clouds

The automatic reconstruction of Building Information Models (BIMs) remains challenging, especially when applied to multi-storey buildings and indoor environments with non-Manhattan layouts and curved structures. To address these challenges, this paper presents a novel method that places Constructive Solid Geometry (CSG) at the core of building reconstruction from point clouds. The methodology also integrates the Segment Anything Model (SAM) and knowledge-based rules to reconstruct as-built BIMs while preserving the geometry and topology of building elements. The proposed approach consists of two main stages: SAM-based segmentation and CSG-based modelling. First, SAM is used to segment rooms, as well as door and window openings. Solids are then generated for the indoor spaces and openings. Finally, a set of Boolean operations is applied to reconstruct building elements, including slabs, walls, indoor spaces, doors, and windows, while subtracting openings of doors, windows, and staircases. Finally, the reconstructed model is encoded with semantic information following the Industry Foundation Classes (IFC) schema. The method was evaluated on seven two-storey building point clouds and demonstrated strong performance, achieving a mean Intersection over Union (mIoU) greater than 90% for floor plan reconstruction, a precision above 87% for door and window detection, and mean geometric deviations below 8 cm for BIM reconstruction.