逆向工程中点云模型孔洞边界的检测是孔洞修补的前提,完美的孔洞轮廓线有利于提高孔洞修补的质量。首先参照二维图像中边界的定义,给出了三维点云模型中孔洞边界的定义;之后通过分析待测点邻域协方差矩阵特征值之间的关系,设计了一种边界点检测算子,用于初步提取孔洞边界特征点;然后采用改进的Kruskal最小生成树算法构建点云最小生成图,并在最小生成图中完成孔洞边界点的排序与孔洞轮廓线的提取。实验结果表明:所提边界检测算子步骤简单,算法效率高;基于计算机图论的孔洞轮廓线生成算法提取的孔洞轮廓线具有光滑、连续的优点,并且在生成轮廓线的同时完成了孔洞聚类。

The detection of the hole boundary of the point cloud model in reverse engineering is necessary for the hole repair, and a perfect hole contour line is conducive to improving the quality of the hole repair. Based on the definition of boundary in two-dimensinal images, the definition of hole boundary in three-dimensional point cloud was given. By analyzing the relationship between the eigenvalues of the covariance matrix of neighboring points, a boundary point detection operator was proposed to initially extract the feature points of the hole boundary, and then, the improved Kruskal minimum spanning tree algorithm was used to construct the minimum generated map of the point cloud. Subsequently, the hole boundary points were sorted and outline of the hole was extracted in the minimum generated graph. The experimental results show that the proposed boundary detection operator has simple steps and high efficiency. The hole contour line extracted by the hole contour line generation algorithm based on computer graph theory has the advantages of being smooth and continuous, and hole aggregation is completed while generating the contour line.