VANTAGE: A Frame-Based Geometric Modeling System Programmer/User's Manual, V2.0

Abstract : Geometric modeling systems allow users to create, store, and manipulate models of three-dimensional (3-D) solid objects. these geometric modeling systems have found many applications in CAD/CAM and robotics areas. Graphic display capability which rivals photographic techniques allows realistic visualization of design and simulation. Capabilities to compute spatial and physical properties of objects, such as mass property calculation and static interference check, are used in the design and analysis of mechanical parts and assembly. Output from the geometric modelers can be used for automatic programming of NC machines and robots. These geometric modeling systems are powerful in many application domains, but have severe limitations to be used for tasks such as model-based computer vision. Among others, (1) there is no explicit symbolic representation of the two-dimensional information obtained by the projection of the 3-D model. The output image displayed on the screen is a set of pixel intensity values, with no knowledge of the logical grouping of points, lines and polygons. Also, the relationship between 3-D and 2-D information is not maintained properly. (2) Most of the current 3-D geometric modeling systems are designed with a closed architecture, with a minimum of documentation describing the internal data structures. Moreover, some of the data structures are packed into bit-fields, making understanding and modification difficult. (3) They run as stand-alone interactive systems and cannot easily be interfaced to other programs.