Research On Key Technologies Of Train Shape Interactive Design Based On WebGL

The research on trains involves many fields. As a technology-intensive industrial products, trains is one of representative industries in Chinese design and manufacturing areas and become the diplomatic card . Shape and appearance design are affected by aerodynamic performance, national culture, personal aesthetic and other factors, complexity of which becomes difficult problems for research workers. At present, the design of the train model rely on many kinds of professional modeling softwares such as UG, CATIA, Solidworks, etc.There are some shortcomings, for example, no-uniform model format, poor interaction way,low design flow convergence and intuitive expression of model. Therefore, to research on the key technologies of train shape designed by better interactive ways will improve the design efficiency. The characteristics of the WYSIWYG can also save the industrial cost. It also offers much reference and application value for other areas of model design.Based on the study of common design methods of train, the design of which is divided two parts in this thesis: model and appearance desgining. In the stage of model designing,based on the Nurbs surface construction theory, scattered data sets ara converted to complete the train 3D model reconstruction and provide convenient interactive ways to modify the model surface. Then, based on WebGL texture mapping and lighting model analysis, the train model will complete the shape rendering and lighting effects simulation to finish the process of train designing. The main work of this paper includes: (1) Based on the traditional point cloud surface reconstruction methods and Nurbs surface structure theories, a train surface reconstruction method which based on the idea of "point-line-plane" is proposed.Firstly, designing a way to pretreatment the scattered cloud data points located on the surface of train model, in which the filtering data reduction algorithm based on sliding window is presented. Secondly, using the Nurbs interpolation principle, the cumulative chord parameter method is used to determine the node vector, and the control points is calculated by combining the joint equations depending on the reduced data. Finally, through the unified curves cluster points which avoid the order and node refinement processing and the design of ridge line generation, the train shape surface reconstruction is achieved through the improved loft surface method. (2) The well-designed model modified scheme with trajectory deformation constraints is presented by discussing the edit ways of reconstruction model and deducing the influence of control points and weight on the lofting surface in Nurbs theory. (3)Based on the study of WebGL texture mapping, Phong material and mixed lighting model,the designing of the train appearance painting and rendering, train parts mapping and train lighting scene simulation are achieved. (4) Based on the research of key technologies such as train surface construction technology, train surface modification scheme, coating design and lighting effect simulation, the Internet-based interactive design experiment system of train shape based on WebGL is realized. With the system’s design and implementation, the good interactivity, real-time fluency and realistic scene is proved, also with the feasibility of the theoretical algorithm.