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+ Author for correspondence.
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helper applications stand-alone applications
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integrated applications.
A helperapplication can only be usedin combination with another application.The helperapplicationthen provides additional functionality. In the caseof a VRML viewer, the viewer itself would be the helper application started by a Web browser such as Netscape Navigator. In contrast a stand-alone application doesnot needany support from another application. A stand-aloneVRML viewer is able to display VRML files without the assistance a Web of browser.Theseviewerscan not only interpret VRML syntax but are also fully capable of the network protocol (seePlate 1). In both cases is necessary it to configure the Web browserso that the VRML viewer is launched.The integratedapplication approachhas the advantagethat the VRML viewer is completely embedded within the main application (e.g. the Web browser). In this caseno additional configuration of the Web browser by the useris necessary. Meanwhile a large number of VRML viewers supporting most hardware and software platforms are available. These viewers provide different user interfaces for browsing and navigation through the
file format. Thus a subset Open Inventor extended of with network functionality became main basisof the VRML 1.0. After the fall conferencePaul Strauss and Gavin Bell extracted the VRML parser library &Lib [3] from the Open Inventor sourcecode,which enabledeverybody to develop a VRML viewer. In spring 1995 at the third WWW conference in Darmstadt, Germany, the specification of VRML 1.0 [4] was presentedand SGI introduced a first browser Webspace.
e.mail:
koop@igd.fhg.de
Abstract-VRML
(Virtual Reality Modeling Language) has already established itself as standard the a for exchange 3-Ddescriptions theInternet. thispaper wantto giveanoverview thecurrentstate of on In we of of VRML andshowseveral areas, whichVRML will develop the nearfuture.A largenumber in in of people involvedin thedevelopment thefutureVRML standard. will givea general are of We overview of the futurecapabilities VRML withoutrelyingon anyparticular of proposal. Copyright0 1996 Elsevier Science Ltd
2. VRML 1.0
VRML is intended by its designersto be the standard language for exchanging virtual worlds (3-D scenes) including interaction possibilitiesand multi-userabilitiesvia the Internet [5]. Therefore the main efforts were laid on the development of a platform independent, extensible and over low bandwidth connections transferrabledescriptionlanguage.The first versionof VRML, VRML 1.O,meets only a subset thesedemands hasthe capacity of but to be extendedto full capability in the near future. VRML 1.0 allows the creation of a static 3-D scene with limited interaction possibilities. Using a VRML viewer, it is possible navigate freely through the to scene and to follow hyperlinks to new 3-D worlds, HTML documentsor other valid MIME types by selecting linked objectswithin the 3-D scene. 2.1. Viewers To make 3-D worlds described VRML visible, by an additional application,the viewer or browser,that interprets the VRML data, is necessary. VRML is currently transferred over a network, using the HTTP protocol. VRML pagesare usually accessed from World Wide Web pages. There are three different approaches how this can be realized: to
Comput. 4 Graphics, Vol. 20, No. 3, pp. 427-434, 1996 Copyright 0 1996 Elswier ScienceLtd Printed in Great Britain. All rights n.wved 0097-8493/96 $15.00+0.00
1. INTRODUCTION
Already a few monthsafter the first Internet browsers were released,Virtual Reality Markup Language (VRML) is established the standard 3-D format as for the distribution of virtual worlds on the Internet. In its initial versionit is still closelyrelatedto existing products. On the one hand the World Wide Web (WWW), which uses same the protocol (H’ITP [I]) to transmit data. On the other hand Open Inventor [2], since the initial draft specification was almost a subsetof it. However, the developmentof VRML has rapidly becomeindependent from its foundations.Currently, VRML is still a static scenedescription language, which doesnot includeinteractive behavior. The aim of this paper is to showthe current state of VRML and to introduce some of the key concepts for extendingVRML in the future. The ideaof a virtual reality interface to the WWW was born and first discussed the first WWW at conference in Geneva, Switzerland, Spring 1994. There the term VRML was coined for the 3-D extensionof the WWW because the relationshipto of HTML. Since VRML enablesthe reproduction of work from an existing solution of 3-D scenes, the term was changed to Virtual Reality Modeling Language. After the conference a mailing list on VRML wasestablished, which had an overwhelming number of participants in a short time. Mark Pesce announced a draft specification of VRML at the WWW fall conference. The VRML community decidedto proceedfrom an alreadyexisting solution dueto time pressures. vote on the future featuresof A VRML and the appropriate basiswasheld, wherea majority voted for Silicon Graphics Open Inventor