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Section 3: Virtual Reality Methods and Techniques#

3.8 X3D#

3.8.1 What is X3D?

X3D (eXtensible 3D) is being developed by the Web3D consortium as the next-generation open standard for 3-D on the web and as a replacement for VRML. X3D has an extensible format which uses XML (eXtensible Mark-up Language) to express the geometry and behavioural capabilities of VRML (see Section 3.7). In developing X3D the aim has been to address the limitations of VRML and to provide a fully specified standard.

The development of the standard has involved a browser working group (including browser companies such as Blaxxun, Nexternet, OpenWorlds and ParallelGraphics) and a task group. The aim has been to develop a standard which can be supported by content creation tools, proprietary browsers and other 3-D applications, and which is also compatible with existing VRML models as well as with the MPEG-4 and XML standards. X3D was launched by the Web3D consortium in August 2001 who made the specification available for implementation and review with the longer-term aim to submit it to ISO (the International Standards Organisation) for ratification. Since then the X3D specification has been actively developed, with the Final Committee Draft (SO/IEC FCD 19775:200x) being submitted to ISO for review in December 2002.

The X3D specification includes backwards-compatible VRML and XML encoding, a Scene Authoring Interface, components to provide extensibility and a lightweight profile that is recognised by MPEG-4. There is also a register of extensions to X3D, including details of their implementation.

3.8.2 Viewing X3D

The X3D browser working group and browser companies have been working to develop viewers which can be used to render both X3D and VRML content. For example, the Java 3D working group (see Section 3.9) and Sun Microsystems have been developing an open source X3D browser called Xj3D. Blaxxun intend to develop their open source Contact VRML 97 browser for use with X3D content.

3.8.3 Authoring tools

Some existing modelling and animation packages already export to formats that are compatible with X3D. For example, Open Worlds is an X3D compatible system that was launched in August 2001 and provides a software developer's kit for 3D multimedia graphics applications. X3D-Edit is an integrated XML authoring tool which allows for VRML to X3D integration and is available from the Web 3D consortium.

3.8.4 Finding out more

Web3D consortium – X3D specification
Web 3D repository – X3D resources including the Open Worlds Horizon Browser, X3D-Edit and XJ3D

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