Research And Application On The Technology Of NURBS Surface Adaptive Mesh Generation Based On Metric Map

Mesh generation is one of important research contents on computer graphics. There has been a great deal of applications of mesh generation on computing and engineering science. Surface mesh generation plays a special role in engineering analysis. The thesis implements adaptive mesh generation of parametric NURBS surface using metric map. The surface mesh is used in a GCAD system DressingSim EX.Our research aims at NURBS surface models. The models are transferred from exterior CAD/CAM system to EX system by IGES files. Chapter 2 starts from the introduction of IGES data exchange file formats. The details of IGES file structures are presented. A back processor of IGES file is designed to extract NURBS surface parametric data.The NURBS surface models from exterior CAD/CAM system only have parametric data. They must be transformed to geometrical model presented by triangular mesh for EX system. In chapter 3, a metric map for NURBS surface triangular mesh generation is described. The detail of data structure for metric map is presented, including a Z-ordering linear quadtree data structure, neighbors navigation equations. Last, a procedure of how to build the metric map using Z-ordering linear quadtree is introduced.A key problem of surface mesh generation by mapping technology is mapping distortion. In chapter 4, based on adaptive discretization boundary of surface, a simple mapping mesh generation method is presented firstly. Then the thesis will describe how to use the metric map in AFM meshing procedure. The details of NURBS surface adaptive mesh generation based on surface curvature using AFM technology with the metric map are presented in this chapter. An algorithm for search remained holes on surface also is introduced.Based on the above research, EX system frame is introduced in chapter 5. Brief introduction on development environment of EX system is described. Detailed description on application of this thesis in EX system is provided as well.Finally, a summary of the thesis research is included in chapter 6. The advices and prospects for the perspectives of technology and application of this project are also included.