| The activities in the information society are of group, interactivity, distribution and collaboration. With all the above features, CSCW is to be widely used in the future. Netmeeting, a kind of typical CSCW application system, is widely adopted nowadays. But all the existent netmeetings manipulate only multimedia information such as voice, video, text, image and so on. The graphics information produced by CAD/CAM system can't work in those netmeetings up to now. Therefore, it is pressing to develop a graphics browser, which can be embedded in net-conferencing system and used to browse distant graphics data and carry out distant discussion.The netmeeting-oriented graphics browser should be characterized by universe, interactivity and synchronization. As to universe, the system is required to read the graphics files produced by all the CAD/CAM systems used widely and currently and display them regardless of the variety of the computer operation system. Interactivity means the user can operate the entities during the conferencing so that it can observe them and get the feature information from different orientations. Synchronization indicates that the netmeeting must synchronize the displaying of graphics in all the users' computers to get the effect of "what you see is I see".Based on all above, the following points are finished in the dissertation:1. Analyzing the working environment of the net browser and put forward its whole frame.2. Reading graphics files and dispersing curves and surfaces. After lucubrating current algorithms dispersing trimmed surfaces, the mapping method is adopted. To avoid unnecessary or repeated calculations, a new tessellation algorithm for trimmed surface is introduced.3. Putting forward an architecture of rendering and interaction module, scene data structure, entity model based on the principles of realistic images. To speed up rendering, some optimization methods are given. Because of high precision of picking in the system, a picking algorithm based on ray-tracing is presented.4. Integrating the graphics browser into the netmeeting, including realizing communication interface, transferring shared data, synchronizing scenes.According to methods mentioned above, a prototype system NetSDBrowser is developed on the Windows 9X/NT/2000 and Unix platforms by C++, OpenGL and IGES. |
