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VIRTUS: A Collaborative Multi-User Platform Kurt Saar Institut fir Betriebs- und Dialogsysteme University of Karlsruhe Kaiserstrasse 12 D- 76 128 Karlsruhe ABSTRACT VRML is a file format for the description of dynamic scene graphs containing 3D objects with their visual appearance, multimedia content, an event model, and scripting capabilities. It is designed to be used on the Internet and on local system and to be used as an exchange tile format. Although equipped with sophisticated techniques for user interaction the current VRML standard still lacks direct support for sharing virtual worlds that can not only be visited but also manipulated by multiple users distributed over the network. Several multi-user technologies have been developed in the past and some use VRML as the rendering and interaction vehicle. This paper gives a short review of design considerations for distributed virtual environments and approaches taken so far in the development of multi-user technologies. We present the design and implementation of VIRTUS, a multi-user platform that allows multiple geographically separated users to enter and manipulate shared VRML scenes. CR Categories and Subject Descriptors: C.2.4 [Computer- Communication Networks]: Distributed Applications - H.5.3 [Information Interfaces and Presentation]: Collaborative Computing - 1.3.2 [Computer Graphics]: Distributed/Network Graphics - 1.3.3 [Computer Graphics]: Picture/Image Generation - Viewing Algorithms; 1.3.6 [Computer Graphics]: Methodology and Techniques - Interaction Techniques; 5.6 [Computer Applications]: Computer-Aided -Engineering Additional Keywords: VRML, Virtual Worlds, Virtual Environments, VRML Event Model, Multi-User Technologies, Distributed Environments, Living Worlds, Collaborative Virtual Environment (CVE), Computer Supported Collaborative Work (CSCW), Architecture Construction Engineering (ACE), Dead Reckoning 1 INTRODUCTION Essentially he WWW is a solitary place where many people see the same information but have no perceptible support for interaction or awareness of one another. Multi-user worlds or DVEs (Distributed Virtual Environments) have the potential to evolve the Web from a pure information space to a social space and to radically alter the way we learn, work, consume, and play from isolated pursuits to collaborative activities. Pelmission to make digital or hard copses ofall or part ofthis work for personal or classroom use is granted wthout fee prowded that copies arc no1 made or distnhuted for prolit or comnicrc~al advantage and that copies bear this notice and the full citation on the first page. To copy otherwise. to republish. to post on servers or to redistribute to lists, requires pnor specific permssion and/or a fee. VRML 99 Paderbom Gemlany Copyright ACM 1999 l-58113-079-1/99/02...$5.00 Steady progress has been made over the last 20 years of research in DVEs and many current systems can portray large, complex, rapidly changing environments containing a large number and variety of actors with some degree of fidelity. But two factors have delayed public interest in DVEs: real time graphics, audio hardware, and networks have not been accessible to everyone. These barriers disappear with the availability of powerful graphics accelerators for PCs, high-speed modems, ISDN-adapters and ADSL. The user interfaces of many traditional and new applications can now take the next step in the evolution from command-line to desktop metaphor to a real 3D-community metaphor which allows us to change virtual worlds and observe changes made by other geographically separated people. Large scale DVEs may turn out to be a new Grand Challenge for computer science. Most of the DVE systems developed so far have been limited to certain platforms, proprietary applications, or network protocols. As the Living Worlds [17] initiative and Open Community indicate there is increasing movement towards open standards. VRML is central to this movement. Since the current VRML standard does not offer language constructs for direct multi-user support most VRML scenes today run on a single machine, have limited interaction and respond to a single user’s input. The implementation and authoring of multi-user environments still requires skilled programmers with thorough knowledge of VRML, Java, JavaScript, and the EAI. We present VIRTUS, a multi-user platform based on VRML2.0, Java and TCP/IP, which eases the development and authoring of distributed environments with a special focus on collaborative work. In a case study we use VIRTUS for architectural construction and engineering purposes. Figure 1: Screenshot of the VIRTUS user interface 141