We will start this section by saying a few words about human senses
and the way in which we affect changes in the world around us. In the rest
of this
section we are going to review the main types of VR systems that are
assuming some degree of standardisation and to attempt to compare and contrast
them in the context of particular VR applications.
Visual cues are by far the most important in most virtual environments although you could imagine a virtual training environment (VTE) for training blind people to learn how to work a guide dog to help them navigate around a town. The VTE would have no visible geometry but would consist of 3D obstacles and sounds etc. We'll come expand on this example below. However, in general it is the 3D representation of the visual world that is most important. Much time and money has been expended on reserching the visual interface both in terms of fidelity but also in terms of stereoscopic vision for headsets etc.
Sound is very important in supporting visual cues with and helps us to understand a lot of spatial information such as being inside or outside, reflected sound etc. We also use sound to locate things by their sound though we are not very good at this compared with many animals. However, if something is represented by both appropriate visual and sound cues it will be more convincing. Sound is also the only genuine 3D sense we have. All others being either very localised or directed as is the case with sight. Sound can of course be represented in mono and stereo as well as 4, 5, 8, and 12 point speaker systems. 3D sound can also be recreated by using head related transfer functions (HRTFs) only require stereo sound systems. There is a short New Scientist article which introduces this technology.
Touch, referred to as haptics in VR, is concerned with both the feel of things, texture, temperature etc., and with artificially creating forces acting which act on our bodies. Efffective deployment of haptics technology into VE would greatly increase the effectiveness of visual and sound cues but is technologically difficult. Some haptics technologies are available both for high end systems and for PCs, ie. force feedback joysticks. Haptics is a very active current reseach field and much information can be found at Haptics Community Web Page.
Smell is receiving some attention and its value in establishing the fidelity of a world is obvious. The smell of the sea on the beach, the pungent odours of a medieval town, cooking and food smells. There have been experimental olfactory systems for the cimema etc. and computer controlled systems with a limited number of smells are quite likely in the not too distant future.
To my knowledge the technology to deploy virtual foods is already widely available in the fast food industry.
What all this basically means is that some 50% of the human sensory bandwidth is covered to some degree of fidelity and this largely the most important part for VR purposes.
Let us now briefly consider the situation with respect to the way in which we affect the world as opposed to how the world affects us. Many of the means by which we affect the world present difficulties for VR systems and for this reason they are often represented by analogues, ie. walking actually being represented by mouse movements. Picking up and moving an object by clicking and dragging the mouse. This is certainly true of desktop VR but also of much high end VR systems. We also affect the world by gestures, talking and issuing commands and requests, by using other technologies such as spades, knives and forks etc., sending letters, making telephone calls and much, much more.
What this all amounts to is that mediating the human senses is a far easier practical proposition than building interface systems to monitor human activity in general. For this reason, VR input systems tend use solely analogues of human activity or analogues in conjunction with particular interfaces such as treadmills etc. In our guide dog example, for instance, a tread mill and some device to represent the handle and motion of the dogs harness etc. would be quite practical.
