Game Development Reference
In-Depth Information
PSA-Peugeot-Citroën group, is that it has a completely reconfigurable structure. Even
though the cube-shaped version (with adjustable width) remains the most standard
configuration, the system can also take form of a flat or curved wall of images. In this
manner, this solution compares with the immersive rooms.
Special devices have been around for several dozens of years and are being used
in transport simulators. The movement simulations are in general linked. A special
solution involves displaying the images on a dome, a technique used for aerial sim-
ulation. Here the dome is a semi-spherical screen of about ten metres and since the
observer is at the centre, he can see 360 horizontally and 90 upwards. To conclude
the discussion about these types of interfaces, we can say that their main disad-
vantages are their extremely high price and their size - whenever video projectors
are used, a large area needs to be provided, which further increases the cost of the
installation.
11.3 PORTABLE VISUAL INTERFACES
Thanks to the boom in virtual reality, a new type of device known as “Head-mounted
Display'' or “Immersive Helmet'' has been developed for vision. The objective of this
device is to provide a stereoscopic vision using two small screens, a large visual field
corresponding to the visual field of the user's eyes and an immersion of the eyes .
The head-mounted display theoretically (but not practically!) aims to be “the ideal
visual interface'' for a single observer. In addition to partial or complete stereoscopic
vision, these devices also have a location sensor tracking the user's head to display
images corresponding to the orientation of his eyes. The direction of the eyes is by
definition the projection of the axes of the eyes on the scene. It is thus the result of
the orientation of the body, head and eyes. Hence, the images displayed in a head-
mounted display correspond to the orientation of the head and not the direction
of the eyes, as no head-mounted display marketed to date can detect the move-
ment of the eyes. In most of the cases, however, it is the direction of viewing. In
fact, visual information is captured in the following manner: First, the eyes rotate in
their orbit and then the head rotates slightly to put the eyes in the middle of their
orbit.
Theoretically the visual field is 360 degrees, considering the movements of the
head. When the head is at a fixed position, the visual field of a head-mounted display
is not as large as it would naturally be (roughly, it is rarely more than 120 degrees
compared to 180 degrees in a horizontal plane), it nonetheless gives an impression of
visual immersion. In natural vision, the perception is clear only in the central field. If
we observe an object on the border of the visual field, we instinctively turn our head
to see it better. The head-mounted displays are thus less effective in drawing the user's
attention to the side, as their field of vision is very narrow. In certain head-mounted
displays with very restricted visual fields, the user feels that he is looking through a
tube, which certainly is an unpleasant feeling. Hence the dilemma of manufacturers:
With a similar screen, if the field of vision is increased by moving the two screens apart
so as to perceive the objects at the side, the zone of superimposition of the right and left
images is reduced and so is the perception of relief. Besides, generally a stereophonic
sound is also offered as these devices have two headphones.
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