Virtual reality interfaces for feature-based computer-aided design systems

A computer-aided design (CAD) system with a virtual reality (VR) interface simplifies the design of complex mechanical parts. To add a design feature (e.g., a hole, slot, or protrusion), the designer can navigate in the part to the appropriate face of the part where he/she wishes to attach the feature, and sketch directly on that face. Besides convenience, this method of feature specification implicitly enforces feature accessibility constraints, and also provides hints to the process-planner regarding the order in which the features may be manufactured. We detail the design of a VR-based prototype CAD system. The system maintains the knowledge of part cavities and their adjacencies, and a triangulated boundary-representation of an approximating polyhedron. We present incremental provably correct algorithms for updating this representation as the user edits the part. We also show how this representation supports real-time displays, navigation, and collision detection. The user-interface of the CAD system relies on these capabilities to provide the above-mentioned advantages. (C) 1997 Elsevier Science Ltd.