Game Development Reference
In-Depth Information
Immersion and interaction are the two key words of virtual reality. The technical
definition of virtual reality is:
Virtual reality is a scientific and technical domain that uses computer science (1)
and behavioural interfaces (2) to simulate in a virtual world (3) the behaviour of
3D entities, which interact in real time (4) with each other and with one or more
users in pseudo-natural immersion (5) via sensorimotor channels.
This definition introduces certain terminology requiring some explanations in
order for us to position it with respect to the points developed in the introduction:
1 It is certainly necessary to capitalise on the potentials of computer science , both
hardware and software, to technically create an interactive virtual environment
that can interface with the user. Simulation is dynamic: Entities (objects, vir-
tual characters, etc.) work in real time as per physical laws (mechanics, optics,
acoustics, etc.) and behavioural laws (psychological, social, emotional, etc.);
2 We use material interfaces of virtual reality, which we call “ behavioural interfaces ''
(refer to chapter 2 of this treatise for this term). They are made of “sensorial inter-
faces'', “motor interfaces'' and “sensorimotor interfaces''. In sensorial interfaces,
the user is informed about the development of the virtual world through his senses.
Motor interfaces inform the computer about man's motor actions on the virtual
world. Sensorimotor interfaces work in both directions. The number and choice
of these interfaces depends on the objective of the application;
3 It is necessary to create a virtual world that is interactive and in real time. The
creation of a virtual world is the main issue of virtual reality: modelling, digitalising
and computer processing of the virtual world. We can note the special case of
associating a real world with a virtual world (techniques of mixed reality);
4 Real-time interaction is achieved when the user does not perceive the time lag
(latency) between his action on the virtual environment and its sensorial response.
This constraint is difficult to fulfil. Failing that, we can try not to cause disturbances
to the subject by time lag, even if he perceives it;
The user must be in the most effective “ pseudo-natural immersion '' possible in
the virtual world. The immersion cannot be natural because we have learnt to act
naturally in a real world and not in a virtual world (sensorimotor biases are created,
that is why the term pseudo ). This sensation is partly a subjective notion which
depends on the application and the device used (interfaces, software programs,
etc.) We will discuss at length the concepts of immersion and interaction which
must be well defined and analysed at various levels.
Achieving the two conditions, interaction and immersion, “perfectly'' with respect
to the planned application is rarely possible. However, they must be achieved in part,
or at least moderately, to be able to speak of a system based on the techniques of virtual
We can derive a fundamental principle of virtual reality from this analysis. This
principle is given in the loop shown in figure 1.2. The user acts on the virtual environ-
ment by using the motor interfaces which capture his actions (gestures, movements,
voice, etc.). These activities are transferred to the calculator, which interprets them like
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