| With the rapid development of the current digital measuring technology, the reverse engineering technology has been widely applied in the projects. Accordingly, the study of reconstruction for surface of point cloud data has also been received significant attention. NURBS surface reconstruction of scattered data and the following of path planning of NC process based on the reconstruction mesh are researched in this thesis.The foundation of geometry topology relation between points each other and being many redundancy data are two great difficulties in the process of reconstruction of scattered data. In order to realize precise compression of scattered data and predigest the establishing process of geometry topology relation, scattered data is converted into scan line data, the point cloud is disposed by the method of direct slicing, the algorithm of intersection between line and surface based on a pair of the least distance relation points and the algorithm of track based on eight directions coding of the section contour data are carried out and the method feasibility is proved by the example.The approximating method of NURBS curve is in detail discussed based on the section contour data. The parameterization of section contour data is carried out by the method of accumulated chord length, the reasonable math model on the selection of node vector is given, the approximating of NURBS curve to section contour data is carried out by the least square method and the most reasonable number of control point is obtained by the dimidiate algorithm, which makes the approximating of NURBS curve reach the extent of complete automation.The technology on obtaining mesh is in detail discussed based on the contour curve. Quadrangle mesh is obtained on the basis of curve compatibility and skinning, the triangulation algorithm is realized on the basis of curve compatibility, the algorithm of triangulation mesh simplification is carried out by computing NURBS curve's curvature and the precision of thesimplified triangulation mesh is analyzed. Finally, the algorithm feasibility is proved by the example.Oriented to NC process, the tool path planning based on STL model is discussed in the thesis. On the basis of STL slicing, slicing data is interpolated by three degrees subsection NURBS curve. After CL data is computed through CC data, the NC tool path planning is realized.Finally, the task in the paper is summarized. The module's interface about establishing model, the whole frame and curve and surface's display under the condition of OpenGL are introduced. A practical project is still put forward in the thesis, which proved the function of the module about establishing model. |
