Virtual Reality (VR) systems (such as the CAVE™) generate images in real-time on the basis of the viewer’s view in the virtual world, so that the viewer sees a three-dimensional view of a given scene. The concurrency and real-time features in virtual environments systems make them difficult to design, implement and test. Collaborative Virtual Environments (CVEs) make this more complicated by adding network considerations into their designs. CVEs demand high Quality-of-Service (QoS) requirements on the network to maintain natural and real-time interactions among users. By using formal methods to model CVEs and analyze their real-time behavior, we can evaluate the network effects on CVEs and the performance of CVEs. To model temporal uncertainties in CVEs, we propose an extension of Fuzzy-Timing Petri Nets (EFTN) in this paper. We give our EFTN models for the CAVE, the TCP protocol and the NICE (Narrative Immersive Constructionist / Collaborative Environments) project and we analyze the network effects on the NICE and the dynamic performance of NICE.

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Zhou, Y., Murata, T., DeFanti, T., Modeling and Performance Analysis Using Extended Fuzzy-Timing Petri Nets for Networked Virtual Environments, IEEE Transactions on Systems, Man and Cybernetics, Part B, vol 30, no 5, pp. 737-756, October 1st, 2000.