3D virtual humans and physical human-like robots can be used to interact with people in a remote location in order to increase the feeling of presence. In a telepresence setup, their behaviors are driven by real participants. We envision that in the absence of the real users, when they have to leave or they do not want to do a repetitive task, the control of the robots can be handed to an artificial intelligence component to sustain the ongoing interaction. At the point when human-mediated interaction is required again, control can be returned to the real users. One of the main challenges in telepresence research is the adaptation of 3D position and orientation of the remote participants to the actual physical environment to have appropriate eye contact and gesture awareness in a group conversation. In case the human behind the robot and/or virtual human leaves, multi-party interaction should be handed to an artificial intelligence component. In this paper, we discuss the challenges in autonomous multi-party interaction among virtual characters, human-like robots, and real participants, and describe a prototype system to study these challenges.

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.

COVEN (Collaborative Virtual Environments) is a European project that seeks to develop a comprehensive approach to the issues in the development of collaborative virtual environment (CVE) technology. COVEN brings together twelve academic and industrial partners with a wide range of expertise in CSCW, networked VR, computer graphics, human factors, HCI, and telecommunications infrastructures. After two years of work, we are presenting the main features of our approach and results, our driving applications, the main components of our technical investigations, and our experimental activities. With different citizen and professional application scenarios as driving forces, COVEN is exploring the requirements and supporting techniques for collaborative interaction in scalable CVEs. Technical results are being integrated in an enriched networked VR platform based on the dVS and DIVE systems. Taking advantage of a dedicated Europe-wide ISDN and ATM network infrastructure, a large component of the project is a trial and experimentation activity that should allow a comprehensive understanding of the network requirements of these systems as well as their usability issues and human factors aspects.

In order to feel the sense of presence in a virtual environment, it is important for the participants to become a part of this environment and interact with it through natural behaviors. This interaction is even more important in networked collaborative virtual environments, in which the participants need to see and interact with each other. We present the Virtual Life Network (VLNET), a joint research effort in the field of networked collaborative virtual environments at MIRALab of the University of Geneva and the Computer Graphics Laboratory of the Swiss Federal Institute of Technology, Lausanne. In VLNET each participant is represented by a virtual human actor with realistic appearance and movements similar to the actual body. Interacting with the environment through his virtual body, the participant is perceived by himself and others in a natural way. Since it is generally not possible to track all degrees of freedom of the human body in order to reproduce realistic body motion, we introduce the motor functions that generate natural motion for standard tasks such as walking and arm motion; they are based on limited tracked information (hand and head positions). By using the same virtual human representation, but with the addition of high-level control, autonomous virtual actors can be introduced into the environment to perform some useful tasks or simply to make the environment more appealing. To further enhance the realistic feel of the virtual environment and to simplify object manipulation we provide the facility of defining object behaviors by attaching motor functions to the objects.