Team : i3d
Section: Scientific Foundations
Keywords : Virtual reality.
We begin by explaining the expression virtual reality. We are not going to propose a n + 1th definition. Instead, we propose to position Virtual Reality by reference to the image synthesis field which is older, better specified but which is nowadays too often confused with virtual reality.
Image synthesis gathers all the techniques leading to the production of images (fixed or animated) representing a numerical model, a scene or a virtual world. To simplify, one can say that image synthesis is a restitution of a virtual scene through a photo album (fixed image) or a film (animated images). Virtual reality makes it possible to enrich perception of the virtual scene by making it possible to the person to interact with this scene. It is proposed to him/her to move from a passive role to an active role, to "live" the virtual experiment instead of being satisfied to view it. By taking again the preceding analogy, virtual reality can be compared with the visit of a country while going on the spot as opposed to the photo report or documentary film. However, contrary to the real case, where the photo report or the documentary film are quite distinct from living the experiment, in the virtual world there is a continuum between the graphic applications and virtual reality. It is mainly the position of this border which is prone to discussions.
A first brief reply is by consulting the various definitions of virtual reality. The concept most usually associated to the expression virtual reality is that of immersion. One speaks about virtual reality when the interaction is sufficiently realistic to get a feeling of immersion, communion, fusion between the person and the application. This concept of immersion remains quite subjective. Should we specify it ? Or isn't it rather prone to a slow evolution accompanying virtual reality research progress ? We choose this second solution and we will be satisfied to enumerate, in no particular order, some factors improving immersion such as stereoscopic visualization, visualization on large screens, head tracking, spatial interaction, superposition of virtual and real spaces, two-handed interaction, multi-sensory interaction, real time simulation. To summarize, we will say that the more numerous are these factors, the stronger is the feeling of immersion and the more justified is the virtual reality expression.