Virtual Reality Modeling Language (VRML)

Background

The first version of VRML (pronounced “vermal”) was released in November 1994 and was heavily based upon the Open Inventor file format from Silicon Graphics, Inc. (SGI). This was superseded in 1996 by VRML2, which ultimately became the VRML97 international standard (ISO/IEC 14772–1:1997) in December 1997. In 2002, an amendment to the standard was published incorporating support for geographic applications (GeoVRML), among other new features.

VRML files are often referred to as “worlds” and identified by a .wrl file extension (or .wrz for gzipped worlds). These world files can be interpreted and displayed by a software program called a VRML browser. These normally take the form of plug-ins for popular Web browsers, though they may also be stand-alone applications. A variety of commercial and open source VRML browsers have appeared over the years.

The VRML97 specification provides support for modeling 3D objects using polygons, lines, points, extrusions, and elevation grids, in addition to various built-in primitives, such as spheres, cones, boxes, and cylinders. Models can specify a range of surface materials, including color, transparency, textures, and movies. Scenes can also include lights; atmospheric effects, such as fog; predefined viewpoints; animation; hyperlinks to other Web content; and sound. The following simple example demonstrates how to create a green sphere using VRML97.

GeoVRML

The VRML97 specification allows users to extend the base format with new functionality implemented in Java or ECMAScript. This was used by researchers at SRI International to develop an extension to VRML97, called GeoVRML, that provides the ability to build or locate models using geographic coordinate systems, such as Universal Transverse Mercator (UTM), geodetic, and geocentric systems. GeoVRML also provides solutions for planetary-level visualization, such as dealing with single-precision rounding [Page 506]artifacts, altitude-scaled navigation velocity, and progressive streaming of large terrain grids. Following this work, a few VRML browsers implemented the GeoVRML specification natively, and it was ultimately included in Amendment 1 of the VRML97 standard in 2002.

X3D

The VRML97 standard is maintained by a nonprofit organization called the Web3D consortium (formerly the VRML Consortium). The Consortium has since developed a new standard to supersede VRML97, called X3D (Extensible 3D). X3D provides all of the functionality of VRML97 but uses an XML format for better integration with modern Web technologies. X3D was ratified as an ISO standard (ISO/IEC 19775) in 2004. However, VRML97 remains an active ISO standard.