Game Development Reference
In-Depth Information
improve the interface, either by increasing the quality of data being transferred between
the subject and the computer, or by proposing a “psychophysical'' improvement in the
sensory stimuli or motor responses. In the first case, the quality of a signal issued by
the interface devices must be improved, for example:
Screening the measurements of a location sensor is often necessary to delete the
signal noises which could disturb the user while handing a virtual object. If the
user blocks the movement of the object, the measurement noises should not move
the object image even slightly. But data screening leads to increase in latency of the
“perception, cognition, action'' loop. Hence one has to try finding an optimum
solution;
Anti-aliasing the computer-generated images helps to improve the visual stimuli
for the subject with respect to the acuteness of human vision, in spite of inadequate
screen quality;
It is necessary to try to decrease the mechanical inertia of a force feedback interface,
but this mechanical problem is difficult to solve using techniques. In some cases,
it could be advantageous to use software programs to help the subject to move
freely. It is possible to order the interface motors to remove, at least partially, the
mechanical inertia during free movements.
In the second case, the psychophysical improvement of the sensory stimuli or
motor responses involves helping the subject, by using software support, to have a
more comfortable sensorimotor behaviour in the virtual environment, for example:
An adaptive spatial frequency filtering of stereoscopic images for their fusion by
the brain (stereopsis) gives a 3D view to the subject, reducing the ocular stress
(refer to chapter 13);
If a user's hands tremble excessively, filtering the data issued by the location sensors
helps to stabilise his actions in the virtual environment.
2.4.3.2 Cognitive Software Aids
The Cognitive Software Aids for motoricity and perception, associated with the VBPs,
help the subject in completing a task. The CogSA can focus either on helping to solve
the sensorimotor discrepancies or on helping the user to complete a task by detecting
his intention. The following examples illustrate the first case:
As mentioned earlier, it is possible to add specific constraints while handling an
object using a 6 DOF sensor and without force feedback, leading to sensorimotor
discrepancies when the object collides with another object. The movements of
the virtual object are restricted to help the user obtain the desired motoricity. For
example, the object's supporting surface becomes parallel to the table surface when
they are close to each other. These unreal constraints are called virtual guides (for
movement) or the effects of magnetism;
For fixed transport simulators having sensorimotor discrepancies between vision
and kinaesthesia, the INRETS ( Institut National de Recherche et d'Etudes des
Transports et de la Sécurité or National Institute of Research and Studies on Trans-
port and Safety) recommends setting up a higher force feedback on the simulator's
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