Game Development Reference
sciences should explore this restrictive field in depth to define practical rules and to
help the VR device designers.
The designers must validate this general design approach at different stages. Let's
not forget that a technical object (therefore a behavioural interface) has multiple func-
tions: The one estimated by the designer and the one used by the operator. The user's
relation of use of an instrument may not necessarily be the one imagined by the designer.
The designer has a technical and functional representation of the behavioural interface
(the technocentric diagram) while the user will only have an external representation
through its effects (for him, it is like a black box, the anthropocentric diagram).
For example, the user's virtual movement on a ground can be via a manual com-
mand (data glove or six-degrees-of-freedom tracker) if we do not want to or cannot use
a moving walkway. However, the user might interpret his commands on the interface
differently than what the designer had anticipated. The problem that the user faces
is the problem of self-representation of his body: Where am I? Where am I going? In
concrete terms, which reference point am I moving? Is it my point of view, is it the
direction of my path or that of the centre of my body? We tested a relative mode of
displacement. The user moves the interface forward to move forward, moves it back to
move back, to the side to sidle along and turns it to swivel. His speed of movement in
the virtual world depends on the distance between the current position of the tracker
and its original position. The movement is stopped by bringing the interface back in
the “dead zone'' which covers the original position. During all these movements, a
virtual hand was used to represent the user's hand on the screen. However, the image
of this virtual hand created confusion. For most of the users, the mode of displacement
was absolute . They were trying to align their virtual hand (and therefore the interface)
with the point they wanted to reach. They were using the following schema: The hand
indicates the direction in which one wants to go, something that the designers had not
anticipated. Some users thought that the hand represented the entire body and were
“teleoperating'' their movement.
To conclude this design approach, let's not ignore the current difficulties in virtual
reality, even if we are using this theoretical and pragmatic model of VR interfacing.
Step 3 (designing of the Behavioural Interfaces on the basis of the VBPs) of this chrono-
logical design sequence is the trickiest stage due to the lack of feedback. On the other
hand, once the VR application is created, assessment of the interfacing, based on the
same model, is possible without any great difficulty (explained in the next paragraph).
2.4.5 Assessment approach
The assessment of the virtual reality system should be based on the general diagram
that we have used earlier. It should not be restricted to the sensorimotor I 2 , which
we come across quite often. We should not aim at making the application as real as
possible, naively thinking that the application will be better if the virtual environment
resembles the real environment. We should refer only to the VBPs required to obtain
the appropriate functional I 2 .
In case of sensorimotor I 2 , the “metrological'' characteristics of the artefact used
(hardware interface) should theoretically be same as the maximum psychophysical
characteristics of the person's senses and motor responses (except in case of particular
exceptions, we compare them with the average human characteristics). It is certainly