Immersive virtual reality is a sometimes vague concept that is used in different contexts. The broadest definition is that immersive virtual reality is a system in which a person feels as if he is truly inside a virtual environment and becomes detached from the real physical world. In theory, this would involve stimulating all of the normal senses in response to actions taken in a virtual world. More practically, the term can be applied to an experience that involves placing a person in a three-dimensional (3D) environment attempting to create an experience that is fully engrossing, although largely visual. The technology to create true immersive virtual reality does not yet exist as of 2011, although many systems have been invented to visually present a situation that mimics actual presence in a virtual environment.
There are two available ways for a person to experience immersive virtual reality. The first is the use of a head-mounted display (HMD) that covers the eyes of the viewer and fills both primary and peripheral areas of vision with images of the virtual environment. The HMD also responds to head movements, allowing a natural visual exploration of the environment.
The second method is to create a cube, or an enclosed space with five or six walls that are actually projection surfaces or displays. A person is then placed inside the cube, which constantly projects images of the virtual environment on every surface, giving the appearance of being inside a digital world. These systems are very expensive, however, and very few of them exist in 2011.
There are other immersive virtual reality hardware devices that attempt to simulate a realistic experience with one or more senses. Haptic systems exist that provide real physical feedback in response to actions in the virtual world. These can be gloves that produce pressure when a virtual object is touched, or harnesses that can vibrate or create other sensations on the body. Some very rudimentary systems also have been created that try to simulate odors with combinations of different chemicals.
The more accurate use of the term "immersive virtual reality" is to refer to a technology goal that has not yet been reached. This goal would be to find a way to completely emulate every aspect of interaction within a completely virtual world. If successful, it would involve the user having such a believable experience that he would respond to a situation both psychologically and physically as if it were real. A system like this would have to be able to simulate every small detail, such as the warmth of sun on the skin or air blowing through hair on the head in a way that would be so convincing as to be indistinguishable from reality.