A Virtual Reality System For Urban Overpass Bridges Based On PKPM3D Graphical Platform

The prompt development of modern software & hardware technology provides us with advantage to develop a new generational bridge CAD system. On the basis of the current states of bridge CAD application and the rapid development of software technology, this paper studies systematically on the software development technology of bridge CAD system, and develops a Virtual Reality System for Urban Overpass Bridges, which is based on the PKPM3D graphical platform of independent intellectual property. This system takes bridge component parametric modeling as the modeling method, and uses virtual reality technology. The study includes:(1) Since graphical platform plays an important role in the CAD system, the paper studies the secondary development characteristic of PKPM3D graphical platform which is of independent intellectual property. And it proves that it is feasible for PKPM3D to take the place of universal graphical platform AutoCAD as 2D or 3D CAD system's developing platform.(2) The approach to enhance the fidelity of the virtual overpass scene is discussed. A combination of geometric-based modeling and image-based modeling technology is used to create the model of the overpass. Texture mapping algorithm and Virtual roaming technique is used to increase the scene fidelity.(3) In the first place, structure and features of bridge is researched, using the design of parametric templates as a guide and applying the modern Programming techniques to create a template library of bridge components which can be expanded. And then a library of bridge components which can be derived is created. Besides, design and develop the windows for bridge parametric modeling module, bridge accessory module and virtual roaming module using MFC and the platform class library. Finally, after the road module is loaded, a Virtual Reality System for Urban Overpass Bridges is accomplished, which is supported by PKPM3D graphical platform and ACCESS database. It fills the gap in China in the field of bridge 3D modeling software which is based on graphical platform of independent intellectual property.(4) According to real project, the software feature is tested. This work proves that parametric modeling method for bridge components is really effective. This method shortens the modeling time and improves the efficiency of design work.