Virtual Scanning Method Based on BIM and Ray Tracing for Occlusion Evaluation and Geometry Extraction

This paper presents a virtual scanning method based on Building Information Model (BIM) which can simulate the real scan process and occlusion condition. The method converts the geometry of BIM into triangular mesh and point cloud. The multilevel data encoding is performed for the triangular mesh and point cloud and an octree is created based on point cloud to accelerate query speed. Two stage intersection tests (ray-octree leaf node and ray-triangle intersection tests) are organized to minimize computational cost. The scanning process of the scanner is parameterized and returns the nearest point with a component label along the emitted ray. The virtual scanning method is validated on a steel structure with over 800,000 triangular meshes.The calculations of over 100 million rays are completed within 10 minutes with serial computation. The visibility ratio of every component is obtained by compare the number of points between virtual scan component and complete component with the same point cloud spacing. Furthermore, the method is validated by comparing the consistency between the virtual scan cross-sections and real scan cross-sections. The real component axis extracted by the registration between virtual scan cross-sections and real scan cross-sections demonstrates better stability.