自由曲面检测中点云偏差色斑图的显示

The Display of Deviation Color Map in Inspection of Free-Form Surface

针对基于实体CAD模型的数字化检测过程中可视化偏差表示的效率问题,提出了一种采用K-D树的近似偏差可视化表达方法.与点到自由曲面精确偏差表达不同,首先对待测CAD模型曲面进行指定尺度的离散,形成CAD模型点云数据.然后,利用K-D树的分治搜索策略,使点与面距离计算近似地表达成点与点的距离计算,使算法的运算复杂度由O(N3)降低为O(N2logN),其表达精度达到全局性观测的目的,并在ACISRⅡ与HOOPS800图形平台上通过结点颜色插值实现点云色斑图的显示.最后,以某型号车灯零件为例进行验证,取得了较好的效果.

It is necessary to improve the efficiency of point cloud deviation＇s visual expression during the inspection of free-form surface based on solid CAD model. A new method was proposed that use K-D tree to describe the deviation of the point cloud to solid CAD model approximately. Differing from the exact description of the deviation calculation, the method firstly facets the surface of inspection in a certain resolution to make a point cloud of the CAD model, then uses the strategy of K-D tree＇s divide and conquer to query the closest point in the point cloud of inspection. The distance between a point to a surface is replaced by one of two points. It makes the complexity of the algorithm from O（N^3） to O（N^2 log N）. The resolution of the method meets the need of observation and the color map is displayed by interpolation of nodes＇ color value in the geometric model system ACISR Ⅱ and the graphic platform HOOPS800. The experimental results of a car lamp indicate that the method is robust and efficient.