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					Technology of Virtual Reality

Overview of VRML
By Azura Mat Salim


Virtual Reality Modelling Language or simply VRML is an international standard file
format for describing interactive 3D multimedia on the Internet. It is not a general
purpose language like C,C++ but instead a scene description language that describes
behaviors of objects in 3D worlds. Also, it does not define an application programmer
interface (API).VRML 1.0 was created based on the Open Inventor file format. Its
capabilities were further extended with the release of VRML 2.0. However, with minor
improvements in its the working draft, VRML97 then replaced VRML 2.0 as the ISO
standard.


Features
VRML defines most common attributes found in 3D applications like transformation,
texture mapping, viewpoints and materials. VRML 1.0 was used to create static scenes
and objects, which was made to be more interactive in the VRML 2.0 specification.
VRML 1.0 lacked in dynamics and multi-user support as well as support for curved
objects (eg NURBS). The introduction of behavior into scenes was the major
enhancement over v1.0, which lead to sharing of dynamically changing geometry and
promotes more interactivity between the user and scene. VRML 2.0 further included
sensors for interaction between objects and events (collision, viewpoint).


 It is relatively easy to compose objects for VRML worlds using a generic text editor,
 similar to HTML. In the VRML 2.0 specification, it can be used both for defining
 VRML documents and or used as a file interchange format. VRML files can refer to
 many other file formats such as JPEG,BMP and GIF being used as texture maps or even
 Java as an independent standard chosen to be used with VRML. VRML also has support
 for various scripting languages (eg Javascript) custom protocol.
VRML uses a hierarchical scene graph in describing 3D objects and worlds. This makes
it easier to create large worlds from smaller parts. Nodes in the scene graph hold their
data in fields and communicate with each other through events. Events are generated
using sensors, which are the basic user interaction and animation of VRML. The VRML
2.0 design enables a prototyping mechanism that allows encapsulation and promotes
reusability of scene graphs using the PROTO statement. It also defines a method to
allow nodes to be external to the VRML file for extensibility using the
EXTERNPROTO statement.


A VRML browser is required to view VRML objects and worlds. It can be a Web
browser plug-in (e.g. Cortona by Parallel Graphics and Cosmo Player or standalone
applications that can view and manipulate VRML worlds (e.g.: Open World, FreeWRL,
an open source VRML browser for Linux).


VRML is most commonly used in creating virtual worlds for architectural
walkthroughs, scientific visualization, and entertainment and industrial designs. With
this, comes the need for creating multi-user worlds where people can meet and
collaborate in various fields. However, in the present, VRML still lacks the networking
and database protocols necessary to create true multi-user interactive 3D worlds. The
present technology of multi-user worlds requires the integration of VRML with other
languages such as Java. The 2 key elements in creating a virtual world are having a text
editor or build tools and a VRML browser to view the world. Basic knowledge in
VRML is sufficient enough to create a decent world but some amount of complex
programming, experience and artistic flair are necessary to create a fast, efficient and
striking world.


Reference
http://www.web3d.org/technicalinfo/specifications/vrml97/index.htm
http://home.hiwaay.net/~crispen/vrmlworks/faq/faq1.html#q1
http://www.web3d.org/vrml/types.htm
http://rikk.best.vwh.net/Book/ch1.htm
Java 3D
By Fadlynna Ilyani Zulkarim


Java 3D is a full-featured 3D graphics API (Applications Programming Interface) that has
the most essential features also found in similar graphics rendering tools. The Java 3D
implementation is layered on top of native low-level rendering APIs, namely OpenGL
and Direct3D. With a comprehensive library of 3D classes, it is a part of the Java Media
family of APIs. It is considered as a high-level programming language because it is based
on Java and it also shields users from low-level rendering details, e.g. hardware
acceleration. It also supports high levels of optimization and multiprocessor rendering.


Java 3D allows us to easily create virtual worlds that are immersive and even interactive.
Like other graphics APIs, it also lets users to deal with lighting, texture mapping and
various other behaviors.


Java 3D has a powerful yet easily mastered graphics capabilities. It is also able to support
applications that operate on a variety of output devices, thanks to its Java predecessors.
An added advantage would be the portability and networking capabilities provided by the
Java platform. A Java 3D applet or application may run on different operating systems,
different low-level graphics APIs or different graphics hardware. Thus, it gives a
platform-independent mechanism for the development of 3D graphics.


Features
   Scene graph programming model: Java 3D is based on high-level scene graph
    programming model. Scene graphs are tree-like data structures used to store, organize
    and render 3D information and Java 3D’s scene graphs are made of objects called
    ‘nodes’. A 3D space that has 3D objects in it is called a ‘virtual universe’, which can
    be viewed on a display device. We can attach the scene graph to the virtual universe
    and changes are made by calling methods to the objects.
   Java 3D rendering control: It has its own rendering control whereby the Java 3D
    renderer can traverse a Java 3D scene graph and displays its visible geometry. It also
    processes user input and performing behaviors. Thus, the developer may have full
    control on the rendering process.
   Scalability: Java 3D was built with scalability in mind. As it is a high-level graphics
    API, it utilizes the hardware acceleration and high-level optimization features (e.g.
    view culling and parallel rendering). As in Java, Java 3D too supports multithreading,
    whereby threads (or lightweight processes) allows division of a program into smaller
    tasks that can be independently executed.
   Convenience and Utility Classes: Basic scene graph construction, mouse and
    keyboard navigation behaviors, etc may be found in Sun’s Java 3D convenience
    classes. This will effectively save the developers’ time and effort and concentrate on
    enhancing the program itself.


Java 3D is basically the Java programming interface for interactive 3D graphics.
Naturally, it provides developers and users platform-independent, high-performance
applications and applets. Since it uses scene graph programming model, it greatly
simplifies programming as opposed to other low-level APIs such as OpenGL and
DirectX. It is an optional package that is installed on top of Java 2.


Reference
Walsh, A.E, Gehringer D., Java 3D API Jump-Start (2002)
http://java.sun.com/products/java-media/3D/
http://www.j3d.org/
http://www.javaworld.com/javaworld/jw-12-1998/jw-12-media.html
MPEG-4
By Chieng Chin Yi


MPEG-4 is an ISO/IEC standard developed by MPEG (Moving Picture Experts Group),
the committee that also developed the standards known as MPEG-1 and MPEG-2. These
standards are what made interactive video on CD-ROM and Digital Television possible.
MPEG-4 is the result of another international effort involving hundreds of researchers
and engineers from all over the world. MPEG-4, whose formal ISO/IEC designation is
ISO/IEC 14496, was finalized in October 1998 and became an International Standard in
the first months of 1999. The fully backward compatible extensions under the title of
MPEG-4 Version 2 were frozen at the end of 1999, to acquire the formal International
Standard Status early in 2000.

MPEG-4 builds on the proven success of three fields:

      Digital television;

      Interactive graphics applications (synthetic content);

      Interactive multimedia (World Wide Web, distribution of and access to content)

MPEG-4 provides the standardized technological elements enabling the integration of the
production, distribution and content access paradigms of the three fields.

Features
The MPEG-4 standard provides a set of technologies to satisfy the needs of authors,
service providers and end users alike.
      For authors, MPEG-4 enables the production of content that has far greater
       reusability, has greater flexibility than is possible today with individual
       technologies such as digital television, animated graphics, World Wide Web
       (WWW) pages and their extensions. Also, it is now possible to better manage and
       protect content owner rights.
      For network service providers MPEG-4 offers transparent information, this can be
       interpreted and translated into the appropriate native signaling messages of each
       network with the help of relevant standards bodies. The foregoing, however,
       excludes Quality of Service considerations, for which MPEG-4 provides a generic
       QoS descriptor for different MPEG-4 media. The exact translations from the QoS
       parameters set for each media to the network QoS are beyond the scope of
       MPEG-4 and are left to network providers. Signaling of the MPEG-4 media QoS
       descriptors end-to-end enables transport optimization in heterogeneous networks.
      For end users, MPEG-4 brings higher levels of interaction with content, within the
       limits set by the author. It also brings multimedia to new networks, including
       those employing relatively low bitrate, and mobile ones. An MPEG-4 applications
       document exists on the MPEG Home page (www.cselt.it/mpeg), which describes
       many end user applications, including interactive multimedia broadcast and
       mobile communications.


For all parties involved, MPEG seeks to avoid a multitude of proprietary, non-
interworking formats and players.
MPEG-4 achieves these goals by providing standardized ways to:
      Represent units of aural, visual or audiovisual content, called "media objects".
       These media objects can be of natural or synthetic origin; this means they could
       be recorded with a camera or microphone, or generated with a computer;
      Describe the composition of these objects to create compound media objects that
       form audiovisual scenes;
      Multiplex and synchronize the data associated with media objects, so that they
       can be transported over network channels providing a QoS appropriate for the
       nature of the specific media objects; and
      Interact with the audiovisual scene generated at the receiver’s end.


Implementation

MPEG-4 Video offers technology that covers a large range of existing applications as
well as new ones. The low-bit rate and error resilient coding allows for robust
communication over limited rate wireless channels, useful for e.g. mobile videophones
and space communication. There may also be roles in surveillance data compression
since it is possible to have a very low or variable frame rate. At high bit-rates, tools are
available to allow the transmission and storage of high-quality video suitable for the
studio and other very demanding content creation applications. It is likely that the
standard will eventually support data-rates well beyond those of MPEG-2.

A major application area is interactive web-based video. Software that provides live
MPEG-4 video on a web page has already been demonstrated. There is much room for
applications to make use of MPEG-4's object-based characteristics. The binary and
grayscale shape-coding tools allow arbitrary-shaped video objects to be composed
together with text and graphics. Doing so, a rich interactive experience for web-based
presentations and advertising can be provided; this same scenario also applies to set-top
box applications. Additionally, it is possible to make use of scalability tools to allow for a
smooth control of user experience with terminal and data link capabilities.

MPEG-4 video has already been used to encode video captures with a hand-held camera.
This form of application is likely to grow in popularity with its fast and easy transfer to a
web page, and may also make use of MPEG-4 still-texture mode for still frame capture.
The games market is another area where the application of MPEG-4 video, still-texture,
interactivity and SNHC shows much promise, with 3-D texture mapping of still images,
live video, or extended pre-recorded video sequences enhancing the player experience.
Adding live video of users adds to the user experience multi-player 3-D games, as does
use of arbitrary-shaped video, where transparency could be combined artistically with 3-
D video texture mapping.


Reference

http://mpeg.telecomitalialab.com/standards/mpeg-4/mpeg-4.htm
Overview of Open InventorTM
By Ernie Darlina Taib


        Open Inventor is an object-oriented 3D toolkit that includes a powerful yet easy-
to-use API for developing interactive 3D graphics applications. It presents a
programming model based on a 3D scene database that dramatically simplifies graphics
programming. It includes a rich set of objects such as cubes, polygons, text, materials,
cameras, lights, trackballs, handle boxes, 3D viewers, and editors that speeds up
programming time and extends 3D programming.
The Open Inventor file format is the basis of VRML (Virtual Reality Modeling
Language) for extending the World Wide Web to incorporate 3D graphics. Because it is
based on OpenGL, it can take advantage of OpenGL hardware acceleration when
available. And like OpenGL, Open Inventor is platform/window-system independent but
provides a rich suite of window system specific components that encapsulate commonly
used tasks in an object-oriented fashion. Written in C++, Open Inventor also defines a
standard file format for exchanging 3D data among applications and platforms.
This toolkit simplifies the software development process and allows very rapid
development of graphics applications. Simple enough to be an integral part of many
computer graphics courses taught at the university level, Open Inventor powers thousands
of production-quality applications used in almost every industry including CAD,
geosciences, medicine, academia, chemistry and movie production.

History
        Open Inventor came to life about 10 years ago. The first beta version of Inventor
(then known as Scenario) appeared in 1991. IRIS Inventor 1.0 was released in 1992. It
was based on GL and hence was not platform independent. Inventor was used in
Showcasetm (a multimedia authoring and presentation tool) by providing support for the
3D Gizmo (3D objects, textures, materials, lights, shadows, customizable extruded
models etc.) After a major revision and rewrite, Open Inventor 2.0 was introduced in
1994. Open Inventor was now based on OpenGL and was licensed to third parties for
porting to other platforms. The same year, a subset of its file format with some additions
was proposed to the Internet community as a possible scene description language for 3D
over the Internet. It was accepted as the VRML standard. The realization of VRML
popularized Inventor to thousands of people all over the world indirectly. Most VRML
authoring applications and browsers are written using Inventor-like APIs.
Over the years SGI has received numerous requests for a GNU/Linux® version of Open
Inventor. By open-sourcing this toolkit Silicon Graphics Inc. (SGI) made it available on
Linux and at the same time enabling this large and very active user community to study,
understand and enhance Open Inventor. Earlier in 2000, SGI released the source code of
the OpenGL Sample Implementation to the open source community, clearing the way for
high-quality OpenGL implementations on Linux. The release of Open Inventor source
codes to the community in August 2000 further highlights SGI's commitment to
providing hardware and software technologies that are relevant to graphics developers.

Design & Architecture

         The Open Inventor toolkit includes: a 3D scene database that includes shape,
property, group, engine, and sensor objects, used to create a hierarchical 3D scene; a set
of node kits that provide a convenient mechanism for creating pre-built groupings of
Inventor nodes; a set of manipulators, including the handle box and trackball, which are
objects in a scene database that the user can interact with directly; and an Inventor
Component Library for Xt, including a render area (a window used for rendering),
material editor, viewers, and utility functions, used to provide some high-level interactive
tasks.
For displaying and interaction the Component Library is the most important part of
Inventor. The component library is window-system dependent but is available for most
platforms thus maintaining the common look-and-feel for applications across platforms.
On X-windows systems, the Inventor Xt Component Library makes heavy use of
Xt/Motif for windows and events. OpenGL is used for all shading, lighting, and drawing
via the GLX extension provided by OpenGL. An inventor scene is an ordered collection
of objects (nodes). The scene database recognizes all the registered inventor nodes. New
nodes and behaviors can be added by the programmer in a number of ways. By using
dynamic shared objects (DSO) the new nodes can be made available to any Inventor
application for reading/rendering. This provides a powerful plug-and-play ability
allowing sharing of data/code among applications. Even if a DSO is not provided for a
new node, alternate representations that use existing nodes can be specified for use with
other applications.


Reference
http://www.motifzone.com/tmd/articles/OpenInventor/OpenInventor.html
http://www.sgi.com/software/inventor/
http://web.mit.edu/1.125/www/OpenInv/openindex.html
http://www.studierstube.org/openinventor/



Other Languages for VR
By Norkhairul Wahab


AC3D

AC3D is popular 3D object/scene modeler available for Linux, Windows 95/NT, and
SGI. It’s very easy to use but powerful too. It outputs POV-Ray, VRML (1 and 2),
RenderMan, Dive, Massive and other formats.


Features

      Multi platform program - AC3D file format compatible across platforms

      Easy to use intuitive interface.

      Built-in fast OpenGL 3D renderer with adjustable field-of-view - instantly see
       results of your actions in 3D. Spin the model or switch into 'walk mode' for
       Quake-style control.

      Headlight and up to 7 possible of lights position.

      24-bit color palette with adjustable diffuse; ambient; emissive; shininess and
       transparency

      Attach URLs to objects for use in VRML files
Minimal Reality (MR)

MR toolkit is a set of software tools for the production of virtual reality systems and other
forms of three-dimensional user interfaces. It consists of a set of subroutine libraries,
device drivers, support programs and a language for describing geometry and behavior.

Benefits

      Applications developed using MR will run at most MR sites with little or no
       modification to the source code.

      The MR toolkit was designed to be easy to extend.

      Complete source code is provided with the MR distribution (Open source).

TCL/TK
Visual Tcl is a high-quality application development environment for UNIX, Windows,
Macintosh, and AS400 platforms. Visual Tcl is written entirely in Tcl/Tk and generates
pure Tcl/Tk code.

Features

      Extensible widget and geometry manager support.

      Create compound widgets and widget libraries.

      Visual Tcl features new ready-to-use widgets: combo box, multicolumn list box,
       progress bar

      Predefined compounds available including scrolled text, scrolled list box, scrolled
       canvas, horizontal and vertical splitters.


X3D

X3D is the next-generation open standard for 3D on the web. It is an extensible standard
that can easily be supported by content creation tools, proprietary browsers, and other 3D
applications. It replaces VRML, but also provides compatibility with existing VRML
content and browsers.


Benefits:
        There are significant commercial and open-source movements for advancing
         X3D.
        X3D content is modular and reusable.
        X3D supports optional XML encoding for tight integration with other Web
         technologies.


Reference
http://www.web3d.org/TaskGroups/x3d/faq
http://www.comp.lancs.ac.uk/computing/users/andy/ac3d.html/


Summary

             VRML         JAVA3D       MPEG-4         Open          AC3D         Minimal     Tcl/Tk     X3D
                                                       Inventor                  Reality
 Genre       File format 3D            Standard        Toolkit      3D           S’ware to App.         Open
             for         graphics      for            & API for     object/      produce    Developme   Standard
             interactive API           interactive    interactive   scene        VR system nt           for 3D on
             3D on web                 video          3D            modeler                 Environ-    web
                                                                                            ment.
 Language    VRML        Java                         C++                        Callable   Tcl/Tk      Multiple
                                                                                 Using
                                                                                 C,C++,Fort
                                                                                 ran
 Multi-                                                                                          
 platform
 Scene                                                                                        
 graph -
 based
 Applica-    Interactive Interactive    Interactive   Interactive   Creation     VR Sys.               3D
 tion        3D virtual 3D virtual      web-based     3D            of      3D   & 3D                   animation
             worlds      worlds        video         graphics      objects      user                   player
                                                      app.                       interface

				
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