A scan-line hidden surface removal procedure for constructive solid geometry

Abstract

This paper presents a new methodology for resolving visible surface images of solid models derived from Boolean combinations of volumetric building blocks. The algorithm introduced here is an extension of well-established scan-line hidden surface removal procedures, and it integrates knowledge of a Boolean construction tree in the surface resolution process. Several hidden surface coherence properties are discussed in terms of their possible exploitation in the intricate solid model visualization process. While many of the earlier coherence techniques depend on a polygon environment in which surfaces and volumes do not intersect, the Boolean process can not afford that luxury because it is inherently required to handle intersecting volumes and surfaces. Initial tests indicate that substantial performance improvements over previous methods can be achieved with the algorithm described in this paper, and that these improvements increase as model complexity increases. An underlying philosophy of a dual solid modeling system is proposed in this paper. It suggests that two solid modelers are necessary to successfully satisfy both analytical precision requirements and user interface visualization requirements. The visual solid modeling task addressed in this paper provides greatly improved response capabilities, as compared to other systems, by striving to optimize the constructive solid model (CSG) solid model computations specifically for display purposes.