Research Of Boundary Extraction And Hole Repairing Algorithm Based On Scattered Point Cloud

With the continuous development of computer technology, reverse engineeringhas been widely used in many fields, such as3D solid modeling and rapid repairingof complex molds, and its essence is to process the point clouds which are obtainedby the3D scanner quickly and effectively. In the process of scanning the mold andthe solid, In the die during the scanning process, the point clouds will not be scannedcompletely because of the mold itself is damaged or the line of sight is blocked, itwill affect the following treatment effects of point clouds directly, so the data must bepreprocessed. For the questions of boundary point recognition and incomplete mouldpoint clouds in reverse engineering, this paper emphatically studies the algorithms ofboundary extraction and hole repairing based on scatted point cloud, and use theWindows operating system as the basis, combined with the OpenGL programmingtechnology in the Visual C++6.0, design and implement the functions ofpreprocessing on point cloud, and achieved the desired results in the experiments ofthe moulds such as turbine blade, the main work of this paper is as follows:(1) Propose an algorithm of boundary extraction based on tangent plane and themean field method. Firstly, use the method of kd-tree searching to establish the spatialtopological relationships and find the K nearest points, use least square method to fitthe tangent plane based on sampling point and its K nearest points, then project thesepoints on the plane, and parameterize the projected points. Then, identify theboundary characteristic points according to the theory of the field force can representsthe average effects of point sets. Finally, connect the characteristic points to eachother with lines on the method of NURBS curve interpolation, improved the visualeffects of the boundary features.(2) Propose an algorithm which is combined with implicit surface and thesteepest descent method. Firstly, homogenize the recognized hole feature polygon,and repair the hole in the two-dimensional space by the thought of local expansion;then, establish the implicit surface for the area of the hole according to theinterpolation constraints and the additional constraints which have already been collected; Finally, accomplish the hole repairing by the way of adjusting the addedpoints which are on the plane to the surface.(3) Design and implement the development of3D point cloud processingsoftware platform. Establish the software platform combined VC with OpenGLprogramming technology. This system has many functions,such as read and displaythe points quickly, interactive control and pickup operation on the points,it canprocess point cloud data quickly and effectively.Experiments show the feasibility andvalidity of the system, it spends1.195s in reading and displaying150000pointobjects.