Virtual reality
Virtual reality, cyberspace, virtual world or virtual environment are to certain extent synonym. Historically the first word used in literature for virtuality was cyberspace~\cite{gibs}. But the most used abbreviation today is virtual reality in public and virtual environment in the science departments. As there exist lots of names for virtual worlds, we have found several definitions describing this term, because virtual reality is not clearly defined. We can say that every department, or even every author adapts definition of virtual reality to his needs.
In qvort they suggest even three definitions of virtual reality. According to Michael Heitu for instance, and as opposed to this definition a positivistic approach can be identified or another opinion - phenomenologic definition.
Definitions of Virtual reality
Definition 1: Idealistic definition.
"Cyberspace" is a space existing in parallel to "real space" with its own, specific laws. Consequently it has its own logics, and its specific metaphysics (or meta-digits).
Definition 2: Materialistic definition.
As opposed to this definition a positivistic approach can be identified. According to this approach even though cyberspace may be technologically advanced, its metaphysical state is quite simple: it is simply a representation of real space. Virtual reality belongs to the same category as drawings, models and photos, that is as something which looks like and thus represents reality.
Definition 3: Phenomenologic definition.
As opposed to this definition a positivistic approach can be identified.
When we build cyberspaces we build space experience representations. This implies that when we create virtual reality models, the basic criterion is not whether they resemble reality, but whether they account for human space representation attributes, that is those attributes which are used in human beings' perception of and being in space and time; the way in which we perceive space (using two eyes and other senses). In [4], [50] and [20] they have another explanation for phrase virtual environment.
Definition 4:
Virtual environment is a synthetic sensory information that leads to perceptions of environments and their contents as if they were not synthetic ~\cite{blasc}.
Definition 5:
Virtual world is regarded~\cite{virt} for a computer-based simulated environment intended for its users to inhabit and interact via avatars.
This habitation usually is represented in the form of two or three-dimensional graphical representations of humanoids (or other graphical or text-based avatars). Some, but not all, virtual worlds allow for multiple users. The world being computer-simulated typically appears similar to the real world, with real world rules such as gravity, topography, locomotion, real-time actions or communication.
Definition 6:
After considering~\cite{gutei} some historical know-hows that Virtual Reality is about creating “acceptable” reproductions of real objects or environments for training, entertainment or design purposes. Virtual Reality uses computers to create 3D environments in which one can navigate and interact.
Definition 7:
~\cite{perceptioncg} Virtual reality is immersive virtual environment that provides a user with the sensory experience of being in a simulated space.
Definition 8:
in ~\cite{hitchhiker} they assume Virtual reality as a computer generated 3D environment within which users can participate in real time and experience sensation of being there.
Every definition has its specifications. But they all have something in common. They introduce the virtual reality as a space parallel to our universe, which has his own rights. But is there something that should have every virtual world?
History of Virtual reality
History of Virtual reality presentation (SK)People tried to represent the world around them from beginning of their existence. From sketching in the caves, through paintings to drawing maps. Maps are probably the most known approach of describing the country. They help us navigate in the environment, in the law or in the army. Actually when we study the chronology of mapcreating we can see that the reputed appearance of the world has changed through the time. The map creators evolved from religious influenced to exact measures and science basements.
Parallel to real world always existed virtual worlds. Worlds that created people in their fantasy to illustrate stories and fairytales or as an escape from the real world to the better one in fantasy. Firstly they describe this imaginary environments only verbally, then with the rise of books they realize, that worlds are sometimes not enough. First noticed map of virtual world created Dante Alighieri in Divine Comedy, when he tried to illustrate his idea of heaven and hell.
The invention of computers provocated the scientists to make virtual worlds more than only static pictures. The history of Virtual Reality as a multi-sensory simulation of the real world can be traced back to the 1960s (in Figure \ref{Figure1.4} marked with red column). The “Sensorama” was a multi-sensory vehicle simulator. The system allowed users to sit in front of a screen where they could choose from different rides prerecorded using motorcycles, bicycles, and even a helicopter.
With Ivan Sutherland came to virtual reality expansion in the field of building extra devices for displaying virtual reality. In 1963 he built drawing simulator “Sketchpad” and in 1968 a head-mounted display that presented a computer-generated 3D scene to the user. The system tracked the user’s head movement to accordingly update the images. Sutherland is commonly recognized as the “father of Virtual Reality systems.”
In early 1970s virtual reality began to divide into three main separated fields. Movies and games are although mainly for entertainment, but without them the development of the simulations and scientific research would be much more slower.
Simulations and scientific research could be not thankful for fast research only to movies and games. For the progress in virtual reality is mostly responsible the military industry.
In 1978 A. Lippman, S. Fisher~\cite{fish2} developed the “Aspen Movie Map.” The application allowed users to view a simulated ride through the city of Aspen, Colorado. The system used photographs of all the streets of the city, taken with four cameras pointing in different directions mounted on a truck. Another exploitation of virtual reality for military purposes was in flight or fight simulators.
In the 1990s, a change of paradigm in VR interfaces occurred with the design of the CAVE. A CAVE is a room with graphics projected from behind the walls. It was invented at the Electronic Visualization Laboratory of the University of Illinois at Chicago Circle in 1992. The images projected on the walls were in stereo to provide a depth cue~\cite{gutei}.
The newest term in virtual reality is Augmented Reality. An augmented reality system generates a composite view for the user that is the combination of the real scene viewed by the user and a virtual scene generated by the computer that augments the scene with additional information. Today Augmented Reality is used in entertainment, military training, engineering design, robotics, manufacturing and other industries.
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