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2.3 VRML - A definition

VRML is an acronym for the Virtual Reality Modelling Language, which was conceived in the spring of 1994 at the first World Wide Web conference, held in Geneva. As a three-dimensional graphical visualisation tool, VRML was intended to become the standard language for interactive simulations within the World Wide Web and was rapidly adopted by the wider internet community. A subset of the Open Inventor ASCII file format was used to form the basis of the language, and the development of VRML was speeded up considerably by the contribution of a VRML file parser into the public domain by the company Silicon Graphics. This and further development took place over the internet via an internet mailing list and later through a number of news-groups.

So what does VRML comprise? A VRML document takes the form of a human-readable text file describing a three-dimensional scene. This text file comprises in effect a list of commands which tell the computer to place objects, of given sizes and colours, at specific locations within a virtual world. Simple objects, for example the lollipop-tree we use as our example, can be constructed out of what are referred to as primitives. These comprise simple, pre-defined geometric shapes, for example cubes and spheres. By extensive use of primitives, very small, neat, files can be produced. More complex objects, for example archaeological landscapes and irregular buildings, cannot be adequately modelled using simple primitives. Here a much more basic building block is used, which can be referred to as a face or polygon. Most landscapes, given their near infinite complexity, require many thousands of individual faces, or polygons, to reproduce their topographic form, resulting in much larger and slower VRML files.

The resultant file, whether composed of primitives, faces or a combination of the two can be distributed over the internet and parsed by a browser program which sensually renders the document into an interactive form. All browsing is done on the client machine resulting in low bandwidth requirements (a whole screen may be smaller than a single rendered image) and hardware independent distribution (screens may be equally viewed on Apple Macintosh, Windows or UNIX based machines).


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