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

摘要

Local updating is a strategy for making incremental changes to a geometric model and its displayed image. Only those parts of a model that are affected by modifications are recomputed and redisplayed, which considerably increases efficiency compared to updating the complete model and its display. Methods are presented for local updating in a solid modelling 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. Special attention is given to precise determination of the screen areas that must be updated. It is performed in three stages: rectangular areas, edges, and parts of scan-lines of interest are successively determined. (Copyright (c) 1988, by Faculty of Technical Mathematics and Informatics, Delft, The Netherlands.)