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Virtual“
refers to its computer-generated existence
Reality
means levels of realistic detail are needed and affordable .
1- DEFINATION
There are many different ways of interpreting the term virtual reality. It can be seen as a technology that enables interaction with 'three-dimensional databases' or as a way of 'integrating man with information'.
This idea of information being at the core of VR is supported by those who promote VR as a method of transferring knowledge or of turning information into knowledge, for example about a route, area or other virtual space
2-DEFINATION
An artificial environment created with computer hardware and software and presented to the user in such a way that it appears and feels like a real environment.
To "enter" a virtual reality, a user dons special gloves, earphones, and goggles, all of which receive their input from the computer system.
. In this way, at least three of the five senses are controlled by the computer. In addition to feeding sensory input to the user, the devices also monitor the user's actions.
The goggles, for example, track how the eyes move and respond accordingly by sending new video input.
The term virtual reality is sometimes used more generally to refer to any virtual world represented in a computer, even if it's just a text-based or graphical representation.
To date, virtual reality systems require extremely expensive hardware and software and are confined mostly to research laboratories
3-DEFINATION
Broadly, virtual reality (VR) is the label given to a range of computer-based approaches to the visualisation of concepts, objects or spaces in three or more dimensions .
4-DEFINATION
VR is as surreal, artificial worlds into which participants are immersed via various futuristic gadgets. Putting this image aside, VR is rapidly developing into a practical and powerful imaging tool for a wide variety of applications. Consequently, when developing VR projects it may be wise to avoid definitions and concentrate on what it is that the technology can do.
ORIGIN OF VIRTUAL RIALITY
As a three-dimensional computer graphics capability, VR enables the developer to create pictorial representations, abstract or naturalistic, and display them, with apparent depth, on a computer screen.
A VR world can simulate the 'real' conditions of a hospital operating theatre, an aircraft landing, or a racing car in a wind tunnel, and it was in just these sorts of simulator scenarios that the earliest VR technologies began to develop.
The power of VR is that it can take the created world, real or fantastic, and allow a user to interact with it. Interactivity is one of the core elements of VR and separates it from other two- and three-dimension.
VR can allow one or many people to interact with computer-generated objects and worlds in the way that they would interact with the real-world (or other) equivalents
A VR world is effectively an interface that gives users some feeling of existence within an artificial world created by computer graphics.
Users may be represented in the world in a range of forms: as a complete virtual body (an avatar), as a part of a body such as a hand or as a controllable viewpoint
FLEXIBILITY AND INTERACTION
Video or paintings can be used to represent certain limited conditions, but a computer-based model is theoretically unbounded.
For example, the same model of an airport may be viewed under a variety of programmed conditions (bad weather, night-time etc.). The scope for designing worlds, and the objects within them, is limitless as real-world constraints, such as gravity, dimension or even common sense, do not have to apply.
A variety of visualisation systems and external hardware devices are used to enable interactions with VR worlds. The level of 'immersion' within a world is dependent upon the devices that are used, and the sort of interactivity that is designed into the world. The most common systems for viewing VR worlds can be summed up as:
Projected. The user's field of vision is effectively filled by screens displaying a projected virtual world. Projection may be onto large concave screens in front of the user or within 'caves' or 'sheds' that users walk into. The latter can fill a 360 degree field of vision
Headsets. Users wear stereoscopic glasses or head-mounted displays (HMDs) which place small screens right in front of their eyes. HMDs enhance users' feeling of immersion/interaction within a world by excluding any glimpse of the real world and by revising the view of the virtual world as the user moves their head to look around
Desk-top. The virtual world is projected onto the screen of a standard computer monitor. This approach relies on interactive features built into the world to provide a degree of immersion for users
Table-top. The virtual world is projected onto a horizontal table-top screen, and is otherwise similar to the desk-top display. It allows interaction in circumstances where a horizontal format is appropriate. For example, a mechanic could learn how to fix a virtual machine in a way that simulates working on a real table-top.
Specialist hardware devices are available that can give users a greater sense of immersion within the world. These devices include the HMD and sensor or data-gloves, which are designed to allow natural movements of the head or the hands in the real world to control movements in a virtual world. However, the standard computer keyboard, mouse, joystick or the more VR-specific space ball (Jern and Earnshaw 1995) can enable a user to control a vehicle, avatar, tool or viewpoint and offer a level of immersion within a virtual world.
The different levels of immersion within virtual worlds can be defined as:
Fully Immersive. An array of VR specific hardware is used to translate a user's natural movements into virtual activity. Devices include the HMD (described above), sensor or data-gloves and sensors attached to a user's body that detect, and translate, real movement into virtual activity (Cress et al. 1997). Devices can also be designed to give users feedback from the virtual world, for example sensations can be stimulated on the skin (e.g. heat or cold) or gloves can physically resist movement when a virtual object is encountered (Luecke and Chai 1997)
Partially Immersive. The hardware that is used in these systems allows users to remain aware of their real-world surroundings rather than being fully immersed in the virtual world. For example, a partially immersive system may include a sensor-glove and a virtual hand but use a desk-top screen for visualisation. In this case, users are fully aware of their surroundings but can interact with the world with natural movements using the glove. Desk-top systems which allow users to control movements using a standard mouse offer a lesser degree of immersion
Partially Immersive. The hardware that is used in these systems allows users to remain aware of their real-world surroundings rather than being fully immersed in the virtual world. For example, a partially immersive system may include a sensor-glove and a virtual hand but use a desk-top screen for visualisation. In this case, users are fully aware of their surroundings but can interact with the world with natural movements using the glove. Desk-top systems which allow users to control movements using a standard mouse offer a lesser degree of immersion
Augmented. In augmented reality systems, users have access to a combination of VR and real-world attributes by superimposing graphical information over the real-world (Kim et al. 1997]. For example, a trainee surgeon could perform an operation on a virtual dummy using HMD or table-top display and a real scalpel. Such a system enables users to develop appropriate motor skills without risk and under a range of different conditions.
Applications
Virtual reality has been described as a 'multidisciplinary effort covering everything from mechanical engineering to psychophysiology' (Rosenblum et al. 1994). The briefest of examinations into the applications of VR will support this idea. The potential uses of the technology are boundless, but there are essentially two approaches to current VR development: modelling the real world and abstract visualisation.