Some Application Of Wavelets In Reverse Engineering

In feature based reverse engineering, surface reconstruction based on sectional curves and surface approximation has been broadly and deeply investigated. A feature based reverse engineering CAD modeling theory has been formed. How to introduce new mathematical methods into reverse engineering to improve the robustness and efficiency of algorithms, and how to use new methods extend existed function to facilitate product redesigning are becoming more and more attractive. Under this situation, the wavelets application in reverse engineering was studied in this thesis.Wavelets application in sectional curve based reverse engineering was studied. The concept scale factor and fluctuation were proposed to analyze sectional curve combined with detail-removed wavelet reconstruction. Based on the analysis, a fairing method of sectional curve-mean coordinate flow was proposed. Wavelets based feature point extraction method of sectional curve was presented. Finally a pipeline surface reconstruction method based on sectional contour was given out.A geometry image based mesh segmentation method was proposed. The parametrization of mesh that homeomorphic to a disk was presented firstly. The formation of geometry image based on geometry information was improved. Two segmentation methods of normal image were proposed. One is based on wavelets reconstruction that the approximation term was removed when wavelet reconstruction. Another one is based on gradient image segmentation method. The threshold segmentation method of curvature image was also studied. All these methods are combined with morphological methods to realize geometry image segmentation.A graph based mesh segmentation method was proposed. Two kinds of undirected, weighted graph were constructed to represent mesh. Vertices and triangles of mesh were taken as elements of graph respectively. The constructed graph was segmented by a disjoint-set forest, so the mesh. The filtering and enhancement of color information on mesh were researched too.A non-uniform B-spline wavelets decomposition fairing method of B-spline curves and surface was proposed. A fairing method of NURBS curve was given out. Different kinds of knot selection methods were used to realize local and global fairing.