Research On Light Weight Product Model For Collaborative Product Development

Collaborative development based on PLM is widely used between companies or in a company. Limited by the bandwidth of network and complex data of 3D models including shape information, construction information, restriction information and feature information, data exchange and data transmission of complex 3D models become a bottleneck problem in a network-based collaborative development environment. To compress data of 3D models in collaborative development environment, several key technologies to simplify the data of complex model are systematically studied in this dissertation. Data of models include geometry information and non-geometry information. In collaborative development environment, non-designers pay more attention to geometry information. Therefore, a method of cutting non-geometry data from model is presented. This method compresses the data of model by drawing out, copying, and reconstructing topology data and geometry data. After cutting off non-geometry, a lot of complex free-formed curves and surfaces are in geometry model. These curves and surfaces are computed by control points. And with the number of control points increment, the data of model increases rapidly. As models need lower precision in collaborative design, a new approach to reduce the numbers of control points of free-formed curves and surfaces is proposed. With the knots vector changed in limited range, the curve and surface can change a little. This approach simplifies curves and surfaces by sampling points, interpolating curves and surfaces, computing error and moving control points to reduce error. In geometry model, interpolation surface almost has lots of control points which make data of surface large. As control points of surface is distributed equably and densely, growing compress method and ratio compress method are proposed. These methods increase the compress ratio of Huffman algorithm based on that the datum between two rows of control points net are almost the same. As an application of the above research, a module of model simplification has been accomplished. And it is embedded into a 3D construction system——GEMS, which is supported by the 863——Hi-tech Research and Development Program of China(Grant No. 2003AA4Z3110) .