Study On Reconstruction Of NURBS Surfaces Based On Re-Sampling

Digital three-dimensional mold repair and visualization is an effective mean to achieve rapid and accurate defect mold, high-quality, high efficiency, low cost repair. With the major manufacturers for mold repair defects and higher requirements putting forward, how to meet the accuracy requirements of the premise of the process itself as much as possible to improve the speed, shorten the production cycle, reduce the cost of production has become the hot spot areas subject. Therefore, this paper complex do some deep research about resampling technique and surface reconstruction and verify research results through system software development with the actual mold.The main research contents are as follows:(1)Curvature of the point cloud data as a basis for processing, in order toimprove the accuracy of estimation of curvature, through comparative analysis of the domestic and foreign scholars on the curvature estimated, propose improvements Meyer optimum algorithm, and experimental verification. Experiment results show that this method for a variety of surfaces can be achieved relatively good results, the obtained average error is low, but also lay a good foundation for the follow-up based on zoning curvature, with its effectiveness.(2)In order to effectively implement the data point zoning propose zoningmethod based on curvature. By comparising the size of the average curvature values with specified mean curvature threshold for each data point,it can divide point cloud data points into feature region and the flat region which is prepared for subsequent re-sampling point cloud data. Experimental results show that this method can effectively implement zoning.(3)For mass processing time-consuming, inefficient results,low accuracy ofsurface reconstruction with point cloud data, an improved resampling algorithm is putting forword. The feature region and the flat areas are sampled on different ways on the basis of the zoning, this method not only retain details of the model feature characteristics, but also allow point cloud data distribution and prevent the emergence of the advantages of a blank area, and own higher surface reconstruction accuracy, reduce the data processing time compared to the only curvature sampling algorithm, which has its practical significance.(4)In order to achieve the establishment of the digitized mold CAD model andthe design and manufacture,do some research about surface reconstruction technology, and put forward NURBS surface reconstruction method. Experiments show that, NURBS surfaces have great flexibility and high efficiency,which can be accurate and simple expression of an existing free-form surface, while enabling the analysis of surfaces, edit, and draw on this basis.(5)In order to calculate the accuracy of NURBS surface reconstruction, putforward an iterative search method based zoning, calculating the shortest distance between point cloud and real fit surfaces. The average deviation test available to fit the shortest distance between the surface and the real point cloud is 0.0186 mm, which achieve the meet of continuity between surfaces.(6)In order to verify the validity of theoretical research, design and build pointcloud data processing software systems. The system based on the single document OpenGL graphics programming environment and vs2012 can complete the whole process from the physical reconstruction of the mold to the CAD model, achieve the reading of point cloud data, display, basic interactions, zoning curvature-based, heavy sampling, NURBS surface reconstruction, preservation and other operations,and can meet the expectations of the point cloud data processing.