In the past decade, networked virtual environments (NVEs) have been an increasingly active area of research, with the first commercial systems emerging recently. Graphical and behavioral representation of users within such systems is a particularly important issue that has lagged in development behind other issues such as network architectures and space structuring. In this paper, we expose the importance of using virtual humans within these systems and provide a brief overview of several virtual humans technologies used in particular for simulation of crowds. As the main technical contribution, the paper presents the integration of these technologies with the COVEN-DIVE platform, the extension of the DIVE system developed within the COVEN project. In conjunction with this, we present our contributions through the COVEN project to the MPEG-4 standard concerning the representation of virtual humans.

In this paper we present a virtual tennis game. We describe the creation and modeling of the virtual humans and body deformations, also showing the real-time animation and rendering aspects of the avatars. We focus on the animation of the virtual tennis ball and the behavior of a synthetic, autonomous referee who judges the tennis games. The networked, collaborative, virtual environment system is described with special reference to its interfaces to driver programs. We also mention the virtual reality (VR) devices that are used to merge the interactive players into the virtual tennis environment, together with the equipment and technologies employed for this exciting experience. We conclude with remarks on personal experiences during the game and on future research topics to improve parts of the presented system.