Quality Detection And Modification Of Curves And Surfaces

The design quality of curves and surfaces greatly influences the appearance of car body. It affects people's first impression to the whole car. Thus affect the power of this automobile in the drastic market competition. Therefore, how to effectively detect and modify the quality of curves and surfaces of car body in a simple way during the design process is always the pursuing target of engineering designers and researchers of this field.On the basis of analyzing the present status of the relative technical research in this field in detail, the technology and theory of computer-aided quality detecting and modifying of curves and surfaces has been thoroughly investigated in this dissertation.A set of surface tessellation algorithm facing to surface quality detection with high quality and high efficiency is put forward. Surfaces are tessellated with 3D equidistant iso-parametric lines by parameters of maximum approximation error and maximum grid size. To better content the requirement of surface quality analysis and modification with local unfairness, the density of tessellation is adjusted by parameters of maximum deviation of normal direction along the grid corner. The information of surface boundary is used to check the public boundary meshes of two surfaces. To raise the connection efficiency of the public boundary meshes and reduce the mesh number when sewing up two surface meshes, connected surface meshes are modified by mesh vertex substitute and mesh deletion according to the certain rule and the demand of the boundary mesh connection.A new method is proposed to quickly build contour lines for surface quality analysis. First, every vertex field value is computed. Then, points with equivalent field value on every mesh edge is judged and computed according to the vertexes related to the mesh edge. Finally, a series of ordinal points with equivalent field value are traced to form contour lines according to the topological relation. In this method, the point with equivalent field value on every mesh edge is estimated and stored only once and the field value of each mesh vertex is also computed and stored only once, which save memory occupation and computing cost when creating contour lines. As a result, the speed of making contour lines and the efficiency of processing contour lines are improved greatly. This algorithm can satisfy the demand...