Scanline Methods for Solid Modelling

The modelling of solid objects is becoming increasingly important in the application of computer graphics to a wide variety of problems, such as CAD/CAM, simulation,and molecular modelling. A variety of methods for rendering solid objects exists, including Z-Buffer, Scanline and Ray Tracing. This paper is concerned with a scanline method for the production ofstill images of complex objects. The implementation of a scanline algorithm is discussed, in conjunction with a consideration of performance in relation to other methods.

Many scanline methods cater only for a restricted class of primitives, such as polygons or spheres. This investigation has resulted in the development of a general purpose scanline algorithm capable of being extended to handle a variety of primitives. The primitives currently available are polygons, spheres, spheres swept along straight-line trajectories, and cylinders, with polygonal models of cubes, cones and cylinders. Additionally, the approach is capable of dealing with ``positive'' and``negative'' volumes, allowing objects with holes to be modelled and displayed.

It has further been extended to cater for the inclusion of transparent objects into a scene, and consequently allows the modelling of coloured "glass'' objects.