AN OVERVIEW OF VIRTUAL REALITY
In our world today we are surrounded by a wonderful array of technologies. We have assimilated many of these technologies into our everyday lives. Increasingly, these different technologies are becoming integrated to provide new capabilities and services. And most frequently a computer is the heart of this integration. This is the case with Virtual Reality - a so-called technology which actually is a very sophisticated integration of a number of technologies.
Virtual Reality is a computer-based technology which incorporates specialized input and output devices to allow the user to interact with and experience an artificial environment as if it were the real world. A VR system permits the user to explore a three-dimensional virtual - or artificial - environment and to interact with lifelike and/or fantasy elements created by the designer. In the virtual world, the user can do things as routine as throwing a ball or as fantastic as flying through space. And these things can be made to occur by something as simple as a hand gesture or a nod or (one day) a sound.
The following is an attempt to provide an introduction to virtual reality and some
of its basics.The technical paper provides a brief introduction to the new emerging technology followed by the two types of Virtual Reality systems viz. Desktop Virtual Reality System and Immersive Virtual Reality System.It also provides information about the various devices that are used for Immersive Virtual Reality System. Paper also covers the characteristics and applications of Virtual Reality. Finally the conclusion provides the importance of this emerging technology and attempts to give a brief look into how Virtual reality can affect the future.
INTRODUCTION TO VIRTUAL REALITY :-
Virtual Reality is generally a Computer Generated (CG) environment that makes the user think that he/she is in the real environment. One may also experience a virtual reality by simply imagining it, like Alice in Wonderland, but we will focus on computer generated virtual realities.
The virtual world is hosted on a computer in the form of a database (e.g. terrain database or environment database). The database resides in the memory of the computer. The database generally consists of points in space (vertices), as well as textures (images). vertices may be connected to form planes, commonly referred to as polygons. Each polygon consists of at least three vertices. The polygon could have a specific color, and the color could be shaded, or the polygon could have a texture pasted onto it. Virtual objects will consist of polygons. A virtual object will have a position (x, y, z), an orientation (yaw, pitch, roll) as well as attributes (e.g. gravity or elasticity). Virtual Reality (VR) provides the experience of perception
and interaction through the use of sensors and effectors in a simulated environment. Advances in simulation technology allow computer resources to be interconnected with humans through the use of sensor systems and robotic devices. The goal of the simulation is to have a viewer see only the simulation -- as if the viewer were inside the simulation itself. Head motion and orientation are used to change the viewerâ„¢s visual perception, making the experience appear real.
The virtual environment (also sometimes referred to as a synthetic environment) may be experienced with a Desktop VR System, or with an Immersive VR System.
DESKTOP VR SYSTEM :- With Desktop VR a computer screen is normally used as the display medium. The user views the virtual environment on the computer screen. In order to experience the virtual environment, the user must look at the screen the whole time.
IMMERSIVE VR SYSTEM :- With Immersive VR the user is 'immersed in' or 'surrounded by' the virtual environment. This may be achieved by using:
1.Head-Mounted Display (HMD)
The head-mounted display (HMD) was the first device providing its wearer with an immersive experience. Evans and Sutherland demonstrated a head-mounted stereo display already in 1965. The EyePhone from VPL Research was the first commercially available HMD (1989).
FIG 1. A HEAD-MOUNTED DISPLAY (HMD)
A typical HMD houses two miniature display screens and an optical system that channels the images from the screens to the eyes, thereby, presenting a stereo view of a virtual world. A motion tracker continuously measures the position and orientation of the user's head and allows the image generating computer to adjust
the scene representation to the current view. As a result, the viewer can look around and walk through the surrounding virtual environment.
The BOOM (Binocular Omni-Orientation Monitor) from Fakespace is a head-coupled stereoscopic display device. Screens and optical system are housed in a box that is attached to a multi-link arm. The user looks into the box through two holes, sees the virtual world, and can guide the box to any position within the operational volume of the device. Head tracking is accomplished via sensors in the links of the arm that holds the box.
FIG 2. The BOOM, a head-coupled display device
The CAVE (Cave Automatic Virtual Environment) was developed at the University of Illinois at Chicago and provides the illusion of immersion by projecting stereo images on the walls and floor of a room-sized cube. Several persons wearing lightweight stereo glasses can enter and walk freely inside the CAVE. A head tracking system continuously adjust the stereo projection to the current position of the leading viewer.
FIG 3. CAVE system (schematic principle)
4.Input Devices And Other Sensual Technologies
A variety of input devices like data gloves, joysticks, and hand-held wands allow the user to navigate through a virtual environment and to interact with virtual objects. Directional sound, tactile and force feedback devices, voice recognition and other technologies are being employed to enrich the immersive experience and to create more "sensualized" interfaces.
FIG 4. A data glove allows for interactions with the virtual world
AN EXAMPLE OF SHARED VIRTUAL ENVIRONMENT :-
In the example illustrated below, three networked users at different locations (anywhere in the world) meet in the same virtual world by using a BOOM device, a
CAVE system, and a Head-Mounted Display, respectively. All users see the same virtual environment from their respective points of view. Each user is presented as a virtual human to the other participants. The users can see each other, communicated with each other, and interact with the virtual world as a team.
6) CHARACTERISTICS OF IMMERSIVE VIRTUAL REALITY :-
The unique characteristics of immersive virtual reality can be summarized as follows:
Â¢ Head-referenced viewing provides a natural interface for the navigation in three-dimensional space and allows for look-around, walk-around, and fly-through capabilities in virtual environments.
Â¢ Stereoscopic viewing enhances the perception of depth and the sense of space.
Â¢ The virtual world is presented in full scale and relates properly to the human size.
Â¢ Realistic interactions with virtual objects via data glove and similar devices allow for manipulation, operation, and control of virtual worlds.
Â¢ The convincing illusion of being fully immersed in an artificial world can be enhanced by auditory, haptic, and other non-visual technologies.
Â¢ Networked applications allow for shared virtual environments.
7) NON-IMMERSIVE VR :-Today, the term 'Virtual Reality' is also used for applications that are not fully immersive. The boundaries are becoming blurred, but all variations of VR will be important in the future. This includes mouse-controlled navigation through a three-dimensional environment on a graphics monitor, stereo viewing from the monitor via stereo glasses, stereo projection systems, and others.
8) VIRTUAL REALITY MODELING LANGUAGE (VRML) :-
Most exciting is the ongoing development of VRML (Virtual Reality Modeling Language) on the World Wide Web. In addition to HTML (HyperText Markup Language), that has become a standard authoring tool for the creation of home pages, VRML provides three-dimensional worlds with integrated hyperlinks on the Web. Home pages become home spaces. The viewing of VRML models via a VRML plug-in for Web browsers is usually done on a graphics monitor under mouse-control and, therefore, not fully immersive. However, the syntax and data structure of VRML provide an excellent tool for the modeling of three-dimensional worlds that are functional and interactive and that can, ultimately, be transferred into fully immersive viewing systems. The current version VRML 2.0 has become an international ISO/IEC standard under the name VRML97.
9) APPLICATIONS OF VIRTUAL REALITY :-
There are numerous applications in the domains of health care, education and lifelong learning, manufacturing, and other areas where this technology shows great promise for improving productivity. Early results show an increase in productivity and a reduction in cost and resources. Examples of current use include: searching of networked databases and libraries; manipulation of molecules for development of nanotechnology devices and chemical systems; shared surgical interventions; modeling, simulation, and analyses; scientific and technical visualization applications; prototyping and planning; and training for and monitoring of complex human-computer tasks.
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Useful applications of VR also include training in a variety of areas (military, medical, equipment operation, etc.), education, design evaluation (virtual prototyping), architectural walk-through, human factors and ergonomic studies, simulation of assembly sequences and maintenance tasks, assistance for the handicapped, study and treatment of phobias (e.g., fear of height), entertainment, and much more.
10) Conclusion :-
A virtual environment can represent any three-dimensional world that is either real or abstract. This includes real systems like buildings, landscapes, underwater shipwrecks, spacecrafts, archaeological excavation sites, human anatomy, sculptures, crime scene reconstructions, solar systems, and so on. Of special interest is the visual and sensual representation of abstract systems like magnetic fields, turbulent flow structures, molecular models, mathematical systems, auditorium acoustics, stock market behavior, population densities, information flows, and any other conceivable system including artistic and creative work of abstract nature. These virtual worlds can be animated, interactive, shared, and can expose behavior and functionality.
In order to keep pace with real-time interaction, virtual reality technology must be supported by high performance computers, the associated software and high bandwidth network capabilities. Virtual reality also requires the development of new technologies such as displays that update in real-time with head motion; advances in sensory feedback such as force, touch, texture, temperature, and smell; and intelligent models of environments.
As the technologies of virtual reality evolve, the applications
of VR become literally unlimited. It is assumed that VR will reshape the interface between people and information technology by offering new ways for the communication of information, the visualization of processes, and the creative expression of ideas.
10) REFERENCES :-
1)Beier Peter,Virtual Reality:A short introduction,http://www-vrl.umich.edu
2)John Vince,Virtual Reality Systems,Addison-Wesley.
3)Rory Stuart,The Design Of Virtual Envoirnment,Barricade Books.
4)John Vince,Essential Virtual Reality Fast :How to understand the techniques and potential of Virtual Reality,Springer Verlag.
5)Jed Hartman,Josie Wernecke,Rick Carey,The VRML 2.0 Handbook â€œ Building Moving World on the Web,Addison-Wesley.