Incremental Display of Constructive Solid Geometry (CSG) Models Using Local Updating

摘要

A local updating strategy for making incremental changes to a geometric model and its displayed image is described. Only those parts of a model that are affected by modifications are computed and redisplayed, which considerably increases efficiency compared to updating the complete model and its display. Methods for local updating in a solid modeling system with a constructive solid geometry (CSG) scan-line visible-surface algorithm that can display shaded images directly from a CSG tree using polyhedral primitives are presented. Precise determination of the screen areas that must be updated is performed in three stages: rectangular areas, edges, and parts of scan-lines of interest are successively determined.