Integration of CAD and virtual reality bases on OMG's CAD services interface

The work presented in this paper concentrates on questions of integration CAD and Virtual Reality (VR). The crucial dilemma is the kind of data handled in both systems: CAD systems on the one hand operate on semantically rich data, where assemblies, parts, features or topological entities can be created and modified. VR systems, on the other hand, mainly operate on dumb triangles.As VR and CAD will remain different areas that will be slow in merging together, we have to find a way to combine both technologies in a single system for VR-based CAD. The first step in this direction is the identification and evaluation of interfaces. In this context, the authors examined the CAD Services interface of the Object Management Group (OMG). The interface not only allows read access to tessellated data, topology and features; it also supports modification of data - especially design features. A software prototype was implemented based on Autodesk's Mechanical Desktop (MD) as a backend CAD system, a partial implementation of the CAD Service interface and ZGDV's VR Framework JSTB, based on Java 3D. The resulting application can be used to visualize arbitrary MD models in an immersive VR environment and interact with the design features of the models. To replace the backend system with any other commercial CAD systems, only the CAD Services interface has to be re-implemented to work on a new set of API functions.The prototype demonstrates the feasibility of this flexible and integrative approach, where a commercial CAD system is linked to a VR environment. Even though the complexity of the models that can be handled in real-time is quite limited in this prototype, the evaluation identifies a high potential of the CAD Services interface. Based on this work, improvements to the interface can be formulated to overcome current limitations of the OMG specification.