边界模型布尔分割环自动识别

Automatic Recognition of Boolean Segmentation Loops for B-Rep Models

布尔分割环是设计特征在边界模型上造型的痕迹,其自动识别是后续设计特征自动重构的基础.在对特征造型过程形状演化分析基础上,提出一种布尔分割环几何表示和自动识别构建方法.首先依据边界的凹凸特性及顶点的邻接特性构建边界模型的特征顶点邻接图,并对邻接图开展顶点节点树搜索;然后将搜索方法分为初始节点选择、节点增长、搜索评估和反向传播4个步骤,在节点增长步骤中,采用相邻节点到特征面距离最小判定方法及顶点虚拟邻接构成伪边的方法,实现分割环的封闭和特征面的有效分割.实例结果表明,该方法能够从复杂特征相交形成的交线中自动识别和构造出布尔分割环.

Boolean segmentation loops are the traces of design features modeled on B-rep models,and theirautomatic recognition is the foundation for the subsequent reconstruction of design features.Based on theshape evolution analysis of the part models in the feature-based modelling process,an approach to automaticrecognition for Boolean segmentation loops is presented.This approach first constructs a feature vertex adjacentgraph of the part model to be reconstructed according to the convex-and-concave properties of geometricedges and the adjacency properties of geometric vertexes,and implements searching for the vertexnode of segmentation loops.Then,the search procedure is divided into four steps,namely the initial nodeselection,the node growth,searching evaluation,and feedback operations.In the node growth step,a decisionmethod in terms of the minimum distance to the feature surface and a method of forming pseudo edgesby virtually linking adjacency vertexes are employed,which can ensure the segmenting loop closed.Theexperimental results show that this method can automatically recognize Boolean segmentation loops fromthe complex intersecting edges formed by intersection of design features.