Papers in PDF format

VRML and the Web: A Basis for Multi-User Virtual
Environments on the Internet
Wolfgang Broll
GMD - German National Research Center for Information Technology
Institute for Applied Information Technology (FIT)
D-53754 Sankt Augustin, Germany
email: wolfgang.broll@gmd.de
www: http://orgwis.gmd.de/~broll
Abstract: VRML is the basis for WWW based 3D data on the Internet. Although VRML was a static description language during its initial phase,
it is currently extended to support interactive virtual environments and behavior of virtual world entities. In this paper we show, how this standard
can be further extended in order to support multiple users and shared interactions. We will also show, how shared applications running on arbitrary
servers may be integrated into this approach. Beside extensions of the language specification itself, extensions to browsers, servers and the
communication protocol will be discussed. We will present a scalable solution based on multicasting.
1 Introduction
VRML -the Virtual Reality Modeling Language- is the standard for 3D data on the Web. In its initial version [Bell et al.
95] [Pesce 95] it was a static scene description language, without any possibilities to realize behaviors or user
interactions. The scene descriptions (world files) are distributed over the Internet by HTTPD servers, using the standard
HTTP protocol [Berners-Lee et al. 95], and displayed on the individual host by VRML browsers such as SGI's
Webspace or our prototype SmallView [Plate 1]. But already after less than one year the VRML community voted on
future extensions in the area of behaviors and multimedia extensions. For that reason six proposals [Broll et al. 96]
[Mitra et al. 95] [VAG 96] for the new VRML 2.0 standard were submitted to the VAG (VRML Architecture Group).
Although there was a wide agreement upon the members of the VRML community to add multi-user support to future
VRML specifications, most of the submitted proposals did not show, how this might be integrated into their behavior
approach later on.
In this paper we will present the key concepts introduced in our proposal, going beyond interactions and behavior, in
order to support multiple users and shared virtual environments based on VRML. We will focus on these additional
extensions, which are rather independent of the final behavior specification and might be added in future releases of
VRML. In the first part of this paper we will show, how the VRML specification can be extended to support avatars,
shared applications as well as shared behavior and multi-user interactions. In the second part of this paper we will focus
on the required network infrastructure, the distribution of avatars and virtual world entity updates.