Overlap Operations and Raster Graphics

Abstract

This paper outlines the development of a volume and surfaces modelling system for use with raster graphic displays. The ideas are presented in a historical framework to make the reasoning behind the design decisions clear and to indicate the main influences which have guided the work. There are two outcomes of importance: a language form for defining volumes and surfaces and hardware to convert this representation directly into a display. The hardware provides hidden-line or hidden-area removal as a display primitive which, in an appropriate implementation, can be fast enough to support a range of real-time display applications. Linked to this hidden-line, hidden-area removal facility is an ability to provide interference tests for objects that are being moved around in a scene. Again there appears to be a hierarchy of applications ranging in complexity from interactive volume editing to robot control and vision systems. The new facilities complement existing point and line based display operations, on which most current displays- hardware is based. A good case is emerging for integrating the two approaches into a single hardware implementation for CAD workstations and for simulator display systems.