A computer-aided design (CAD) system with a virtual reality (VR) inter
face simplifies the design of complex mechanical parts. To add a desig
n feature (e.g., a hole, slot, or protrusion), the designer can naviga
te 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 conv
enience, this method of feature specification implicitly enforces feat
ure 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 m
aintains the knowledge of part cavities and their adjacencies, and a t
riangulated boundary-representation of an approximating polyhedron. We
present incremental provably correct algorithms for updating this rep
resentation as the user edits the part. We also show how this represen
tation supports real-time displays, navigation, and collision detectio
n. The user-interface of the CAD system relies on these capabilities t
o provide the above-mentioned advantages. (C) 1997 Elsevier Science Lt
d.