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Introduction to VRMLIntroductionOne aspect of multimedia which has received a great deal of attention recently is Virtual Reality. There are a number of technologies associated with Virtual Reality, from full immersive environments to three dimensional representations on a standard monitor. This paper will provide a brief overview of just one of these technologies, VRML.The Virtual Reality Modeling Language (VRML, often pronounced 'vermal') was designed to allow 3D 'worlds' to be delivered over the World Wide Web (WWW). VRML files are analogous to HTML (hypertext markup language) files in that they are standard text files which are interpreted by browsers. Indeed, the original name suggested was the Virtual Reality Markup Language. Like HTML, VRML has been designed to be platform independent and to work over low bandwidth (i.e. low speed) connections. While HTML files describe a 2D page containing various text constructs, such as paragraphs and headings, VRML files describes a 3D space, or 'world'. Using a VRML browser the user can explore this world, zooming in and out, moving around and interacting with the virtual environment. This allows fairly complex 3D graphics to be transmitted across networks without the very high bandwidth that would be necessary if the files were transmitted as standard graphic files. VRML can also include multimedia elements, such as texture images, video and sounds. VRML filenames end in ".wrl", ".wrl.gz" or ".wrz", the latter two denoting that the files have been compressed (by a program called gzip), often being only 1/10th their uncompressed size. Most browsers, once correctly configured, will automatically uncompress the files. A VRML world is made up of lots of simple shapes, such as cones and spheres, grouped together to form objects. The more shapes in the file, the more detailed the world, but at a cost of increasing the file size and the time taken by the browser to display the world. One reason why VRML in particular, and virtual reality in general, has become more accessible recently is the increasing availability of relatively low cost, fast graphics cards and 3D accelerator chips, which allow complex worlds to be drawn quicker. HistoryVRML has its origin in Silicon Graphics Inc.'s (SGI) Open Inventor 3D graphics programming language. After a session at the First WWW Conference, the VRML 1.0 draft was created, with Mark Pesce, Anthony Parisi and Gavin Bell being the prime movers. The VRML 1.0 specification was first published in May 1995, and the first VRML browser embedded in a HTML browser (a 'plug-in'), WebFX, was introduced in August 1995. Although work began on version 1.1 later that year, it was later abandoned, and a request for proposals issued for a VRML 2.0 standard. SGI's "Moving Worlds" proposal was finally accepted as the VRML 2.0 standard in August 1996. VRML 2.0 was renamed VRML 97 and formally accepted as an ISO standard in December 1997.The biggest difference between VRML 1.0 and 2.0 is the degree of interactivity, where VRML 1.0 produced static worlds, VRML 2.0 can produce dynamic, multimedia worlds. Sound and video clips can be incorporated within the world, objects can be programmed to move and react automatically or to user input or the passage of time. To achieve this many new nodes were introduced, and most existing ones modified in some way The LanguageVRML files consist of collections of objects, called nodes. Nodes can be grouped into three main types:
For example, the following VRML code describes a tree trunk:
#VRML V2.0 utf8 the header - the first
line of every VRML file.
Separator { start of grouping node
Texture2 property node within the
group
{filename "bark.jpg"} the image file to be used as
a texture
Cylinder { shape node, which will be
parts ALL modified by the texture2
radius 0.5 node
height 4
}
}
The comments in italics on the right should be removed before trying to load this example. Comments can be included in a VRML file by starting the line with #, as in the header line.
Other nodes are also defined which do not fit into the three main categories. These include nodes which define the light source and viewpoints, allowing the user to select different views, for example from the 'front' or 'back' of the scene.
BrowsersThere are many VRML browsers available. Most of these are plug-ins which display the scene and provide user interface controls within your Web browser window. A few, however, are separate 'helper' applications. Most browsers allow you to move through a VRML world in several ways:
Authoring ToolsTo produce simple worlds, a text editor and a knowledge of the VRML specification is all that is required. However, as worlds become more complex, there are additional tools which can help. These fall into two categories, modelers or 'world builders' and conversion or translation programs.ModelersA VRML modeler is a 3-D drawing application which can be used to create VRML worlds. Some examples include:
Conversion programsConversion programs take output from other packages and convert it to VRML. Common formats which can be converted to VRML 1.0 and/or 2.0 include:
For links to many VRML sites, news updates and related reports see the VRML and Java 3D Information Centre at http://www.scs.leeds.ac.uk/vrmljava3d/ VRML in useVRML has been put to a variety of uses in higher education, from architecture through to medical applications, and indeed could be used anywhere where there is a need to view 3D objects. A few examples are given below to illustrate this wide variety of uses.
The FutureA number of working groups hosted by the Web 3D consortium (formerly the VRML Consortium) are looking at many different aspects of VRML. These include:
Further Information
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