MODELER-INDEPENDENT FEATURE RECOGNITION IN A DISTRIBUTED ENVIRONMENT

Solid modelers and other CAD/CAM subsystems are moving to distributed heterogeneous computing environments, so as to support design and manu facturing processes that are temporally and spatially distributed. Com munication and collaboration among the software components of such dis tributed systems require protocols for accessing remote objects. This paper discusses an approach that provides transparent access to divers e solid modelers in a distributed environment. A solid modeler is augm ented with a software wrapper, called an adaptor, so as to provide a u niform application programming interface (API). Applications interact with the uniform API and need not concern themselves with the specific s of the modeling systems used. API calls are implemented in a client- server architecture, in which a modeler and its adaptor function as a geometry server, and various applications communicate with the server through remote procedure calls (RPCs). A few adaptors have been implem ented at the University of Southern California's Programmable Automati on Laboratory, and have been used routinely for several years. This pa per discusses adaptor design problems and our approach to their soluti ons. It illustrates the application of our methods through an example that involves the incremental recognition of machinable features in a distributed environment. This environment includes a geometry server, a simple feature-based design system, a state-of-the-art feature recog nizer, and a graphics renderer, all running as separate processes in d ifferent machines. To our knowledge, this is the first documented effo rt in which a complex application such as feature recognition is capab le of running, unmodified, on top of modelers based on constructive so lid geometry or on boundary representations, which are fundamentally d ifferent. (C) 1998 Elsevier Science Ltd. All rights reserved.