Arbitrary cut algorithm based on 3D geological objects represented by TIN structure

This paper presents a novel arbitrary cut algorithm based on 3D geological objects represented by TIN structure. The geological model is composed by a series of TIN surfaces. Compared with the classical cut algorithm, the algorithm brings some obvious improvements on the following two aspects: the generation of arbitrary section and the partition of cut geological bodies. According judging the position between cut object with the geological model, the result section can be generated. And different methods can be used to deal with different cut types. The thesis gives a new algorithm based on oriented bounding box tree (OBBT) to judge between point and polyhedron to solve the above problem. It converts the complex cutting problem to a series of simple operations: collision detection, intersection between a line segment and a triangle, triangle mesh reconstruction, the position test between point and curve or surface, etc. It use geometric surface or geometric entity to cut any geological model according to the algorithm. Therefore, users can analyze the interior structure of any geological model efficiently. By testing with some underground geological model of Shanghai, China, the algorithm successfully solves the problems of 3D geological models analysis such as arbitrary cutting, generating fence diagram, foundation ditch digging, pit excavation, tunnel digging and virtual drilling.