NAG Ltd, Wilkinson House,
Jordan Hill Road, Oxford OX2 8DR, UK
Abstract. The Virtual Reality Modelling Language (VRML) is used to publish 3D scenes on the World Wide Web. In this paper, we give a brief account of the development of VRML and discuss its use in the context of scientific visualisation. We pay particular attention to the new features that have been added to the language at version 2.0, and assess these for their utility in sharing visualisations of complex 3D datasets. Chief among the new features is the ability to add behaviour to the scene, and we present a number of examples (garnered from our own work, and scenes which we have discovered on the Web) of dynamic visualisations which make use of these enhancements. Finally, we describe some of the shortcomings which we perceive in VRML 2.0, and indicate ways in which the language could usefully evolve in the future.
Introduction
The World Wide Web (WWW) has had an enormous impact on the way in which information can be shared between disparate locations. Many factors have contributed to the explosive growth in its use, but the initial impetus undoubtedly came from the definition of a language--the well-known HyperText Markup Language (HTML)--for the description of text, images, sound, movies and other types of data that can be published on servers around the globe. Once this language had been defined, the way was clear for the development of browser and authoring tools for documents composed of these datatypes.
For some time now, this list of `Web-aware' datatypes has been supplemented with 3D geometry, owing to the definition of a language for describing 3D scenes on the WWW. The Virtual Reality Modelling Language (VRML) is a standard for the interchange of 3D data and, following the definition of version 1.0 of the language in 1995, the number of sites which offer 3D scenes has increased dramatically, in a fashion that parallels the overall growth in WWW activity.
A new version--2.0--of the language was defined in 1996. The major enhancement over version 1.0 is the introduction of behaviour into the scenes which may be described using this language. This leads to the possibility of sharing geometry which is dynamically changing, and new ways for the user to interact with the scene. In this paper we examine some of the implications of VRML for the field of scientific visualisation. We present several examples of visualisations which have been created in VRML, paying particular attention to those which make use of the new features of VRML 2.0. Some of these scenes have been developed at NAG, but there are others which have been downloaded from other sites on the Web.
Our paper is arranged as follows. We give a brief survey of the history of VRML in the following section, and describe its relationship to the Open Inventor[4] graphics library. We then (SS2) present three examples of the way in which VRML has been used as a delivery mechanism for sharing visualisations on the WWW: a Visualisation Web Server, which allows users to produce visualisations of their data over the Web, with the results being returned to them as VRML; a molecular hyperglossary, where VRML is used as an enabling technology in the exploration of multidimensional data spaces; and finally, an airline planning system. Here, several datatypes are displayed in the same space to produce a visualisation of airline routes, which is then shared with remote sites (actually, the control towers of interested airports) via VRML. Section 3 contains a description of the new functionality that VRML 2.0 offers over version 1.0 of the language, followed by a number of examples of its use. Some of these have been constructed using IRIS Explorer [5], a data visualisation toolkit based on Open Inventor. Finally, in Section 4, we attempt to assess VRML as a language for scientific visualisation, discussing the parts which we have found to be useful, the parts which have received less attention and outlining ways in which it could be further enhanced in the future.
[3] David Knight
[4]. Wernecke, J. (1994) The Inventor Mentor. Programming Object-Oriented Graphics with Open Inventor, Release 2, Addison-Wesley.
[5]. The Numerical Algorithms Group (1995) IRIS Explorer User's Guide.