STL模型布尔运算的实现

Implementation of boolean operations on STL models

首先建立STL模型的拓扑结构从而获得三角面片间的相邻关系.通过两个实体间的棱面相交性测试获得交点和交线,进而提取交线环.利用约束Delaunay方法对相交的三角形进行二次三角形划分,将相交表面沿交线环剖分为多个面域,利用射线法判断各个面域相对于另一实体的位置关系.通过提取相交环来决定有效的相交线降低了位置关系判断的复杂性,提高了布尔运算的稳定性.

The topological structure of STereo lithography（STL） models was built in order to obtain the neighborhood relationship among the triangular facets. The intersection test between every edge of one solid and every facet of another solid was taken to get the intersection points, the intersection seg- ments and the intersection loop. The intersected triangle was subdivided by the constrained delaunay triangulations. The intersected surfaces are divided into several surface patches along the intersection loops. The inclusion between the surface patch and the other solid was taken by Ray-Method. Detecting the loops for determination of the valid intersection lines greatly increases the efficiency and the reliability of the process.