Virtual assembly modeling based on hierarchical and constrained structure

In order to solve the problems such as information completeness and model complexness of assembly modeling in virtual environment, a hierarchical and constraint-based virtual assembly model is proposed in this paper. This virtual assembly model includes product layer, component layer, part layer, feature layer, surface layer and polygon layer, the hierarchical mapping relationships are existed among the elements in different layers, and the constraint relationships are existed among the elements in the same layer. Based on data transformation from CAD to virtual reality system, the generation algorithm of the virtual assembly model is realized, and the structure of virtual assembly scene graph is given. The hierarchical and constraint-based virtual assembly model has high integration of information and can satisfy the real-time demands, and it is convenient to be integrated with CAD systems and scene graph. The examples are given to demonstrate the effectiveness of the proposed virtual assembly as well.