3D Mesh Models Segmentation And Modeling Of Automobile Appearance Design

In recent years, with the rapid development of digital geometry processing and 3D scanning technology, the three-dimensional geometric model of the emerging digital media has been further developed and applied. The quantity and quality of the 3D model is also improved continually, so people begin to think about how to reuse the existing 3D models so as to decrease the cost of manpower and financial resources in redesigning the model. Based on the current situation, this paper summarizes the segmentation of the three-dimensional model, the research progress of interactive modeling and its application in various fields in the current international and domestic. And then taking the automobile appearance as the research object, a new method to realize auto appearance design is put forward, using the mesh segmentation and splicing. In this paper, main research contents and innovations are as follows:(1)After analyzing and comparing the mesh segmentation method based on the boundary and region, a method to split auto appearance model according to the remarkable features and recessive features is put forward. For the segmentation of remarkable features, the remarkable features regions in the model, including corners, valley lines, inflection points, ridges, edges, boundary lines and so on are extracted by using the method of "minimum rules" and the model feature point set is also confirmed. In the form of single seed point or multiple seed points, using the analysis method of principal components, the main direction of feature point set is obtained. Then along the main direction, a new feature point is found as the next iterative point, iterating in turn until finding the initial feature point or unable to find the next iterative point. Finally, using B-spline curve, matching these feature points one by one forms a splitted loop. For the segmentation of recessive features, in the way of specifying multiple points, a closed geodesic cubic B-spline curve is directly generated to form a splitted loop. Using the above segmentation method can achieve different users’ segmentation requirements for different parts of different car models.(2)Through a comparative study on some commonly used mesh deformation methods, the process of mesh edit and deformation is divided into two stages: global deformation and local deformation stage. In the global deformation stage, the NFFD free deformation method is used to deform the splitted parts as a whole. However, the point-constraints free-form deformation method is used to deform the local characteristic of splitted parts for making up the deficiency of NFFD in the local deformation stage. Meanwhile, in order to edit and deform the local details much better and ensure the surface smoothing degree after deformation, point-constraints free-form deformation method is improved and a deformation method is proposed, which is to determine the deformation region using the k ring neighborhood search based on local refinement.(3)A method is proposed to splice the components of auto mesh models using the implicit curved surface which is based on radial basis function, and the mesh splicing process is mainly divided into the following steps: the pre-processing of mesh components, extract splicing boundary, pretreatment of splicing boundary, establish the implicit curved surface equation of splicing area and display the meshing of implicit curved surface, so that components from different cars can be combined together to generate a new gird model, which can realize the rapid prototyping of the auto appearance.