建筑CAD及其实时漫游技术

一个完整的建筑造型通常都包含１０几万乃至上百万个多边形，若要在这样的环境中作实时漫游，则必须进行可见性预处理．通常当视点位于建筑物的内部时，只有少数面是可以看见的，而绝大多数面都被遮挡住了．如果能够只对这一小部分面进行消除或渲染处理，就可以大大提高计算速度．本文根据建筑ＣＡＤ的特点探索了一种基于“房间”结构的可见性预处理方法，这种方法速度较快，而且容易实现．在实时漫游中，只需根据预处理结果从视点所在房间的数据结构中提取相关的可见面进行计算，而不需处理整个建筑模型，从而大大提高了实时计算的速度．实践证明，采用可见性预处理技术，在微机上实现快速动态消除，在速度上可以满足实时漫游的需要．

VISIBILITY PREPROCESSING AND INTERACTIVE WALKTHROUGHS FOR ARCHITECTURAL CAD

Usually, a whole architectural model contains millions of polygons. Visibility preprocessing is necessary for real time walkthroughs in such an environment. When the viewpoint is in the building, only a small part of polygons can be seen by the viewer, the others are all hidden. The display will be speeded up if people just compute this small part of polygons. In this paper, an efficient algorithm of visibility preprocessing based on the "room" structure is proposed. During the real time walkthroughs, the visible polygons instead of those of the whole building are retrieved from the database and are sent to the hideor render pipeline.