The Common Geometry Module (CGM): A Generic, Extensible Geometry Interface

Geometry modeling has in the past five years emerged as a commodity capability; several geometry modeling engines are available which provide largely the same capability, and most high-end CAD systems provide access to their geometry through APIs. However, subtle differences still exist between these modelers, both at the syntax level and in the underlying topological models. A modeler-independent interface to geometry is critical to solving many of the geometry-based problems which exist in applications like mesh generation. The Common Geometry Module, or CGM, provides such an interface to geometry. CGM consists of a set of wrapper functions which translate function calls such that they access geometry in its native format. However, CGM also provides functionality not found in most modelers, like support for non-manifold topology, and alternative geometric representations, including mesh-based and facet-based geometry. CGM is designed to be extensible, so that applications can define application-specific behavior for geometry entities. CGM is also designed to be easily portable to other geometry modeling engines. Ports to SolidWorks and Pro/Engineer are underway. 1 SANDIA IS A MULTIPROGRAM LABORATORY OPERATED BY SANDIA CORPORATION, A LOCKHEED MARTIN COMPANY, FOR THE UNITED STATES DEPARTMENT OF ENERGY UNDER CONTRACT DE-AC04-94AL85000.