virtual reality, while initially focused on immersive viewing via expensive equipment,
is rapidly expanding and includes a growing variety of systems for interacting with 3D
computer models in real-time.
From an immersive graphical point of view, virtual reality can also be classified as
Full-immersive3Dgraphic: Full immersive systems include full scale representa-
tion, stereoscopic viewing, and head-referenced navigation. The term virtual real-
ity initially referred to these systems. Head-mounted display (HMD) is currently
commercially available for providing users with a certain level of immersive virtual
Semi-immersive3Dgraphic: Semi-immersive systems include large screen projec-
tions with or without stereo or table projection systems.
Non-immersive 3D graphic: Non-immersive systems only have monitor-based
viewing of 3D objects. This is the simplest way to display a virtual reality world
through the use of appropriate projection. Most Web-based virtual reality systems
are currently used on the use of non-immersive technology due to hardware, cost,
and bandwidth constraints.
As applications of virtual reality, virtual world or virtual environment (VE) is often used
to refer to the use of 3D graphics, 3D sound, and real-time interaction in an environmental
simulation. Specifically, a VE is an environment, which is partially or totally based on user
or computer generated sensory input, which may include information from the three most
important senses of sight, hearing, and touch.
Web-based vIrtual realIty
The rapid development of the World Wide Web in recent decades has created an important
variant of virtual reality applications, that of Web-based virtual reality. Applications in this
domain are usually developed using the main programming languages of virtual reality
modeling language (VRML) as well as the 3D API extension of the Java language. The
former is a specification obtained from an extended subset of the SGI Open Inventor scene
description language, which is a higher level programming tool for OpenGL.
Figure 3 presents the relationship between VRML and Java 3D. As shown, a 3D Web-
based application will have programming codes in Java or Java3D in general. Some of
these codes would invoke the Java3D API, which will in turn invoke lower level routines
in libraries such as DirectX or OpenGL.
Regardless of the programming language used, a Web-based 3D application is typically
carried out through a browser working under a client-server approach. The 3D plug-in that
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