Virtual Reality is classified into three major types: (a) Non-Immersive Virtual Reality Systems, (b) Semi-Immersive
Virtual Reality Systems and (c) Immersive (Fully Immersive) Virtual Reality systems.
a. Non-immersive Virtual Reality systems
It involves implementing Virtual Reality on a desktop computer. This class is also known as Window on World. Using the desktop system, the virtual environment is viewed through a portal or window by utilizing a standard high resolution monitor. Interaction with the virtual environment can occur by conventional means such as keyboard, mouse or trackball
b. Semi-immersive Virtual Reality systems
A semi immersive Virtual Reality system comprise of a relatively high performance graphics computing system which can be coupled with either a large screen monitor; a large screen projection system or multiple television projection system. Using a wide field of view, these systems increase the feeling of immersion or presence experienced by the user and stereographic imaging can be achieved using some type of shutter glasses.
c. Immersive (fully immersive)Virtual Reality systems
An Immersive Virtual Reality system is the most direct experience of virtual environments. Here the user either wears an head mounted display (HMD) or uses some form of head-coupled display such as a Binocular Omni-Orientation Monitor (BOOM) to view the virtual environment, in addition to some tracking devices and haptic devices. An HMD or BOOM uses small monitors placed in front of each eye which provide stereo, bi-ocular or
monocular images.