Game Development Reference
In-Depth Information
Figure 11.6 Hot spot at the centre of the screen due to a bad diffusion of the projected light
projected image. The screens can be flexible or rigid. Flexible screens are easy to carry
and do not block sound waves, which makes it possible to provide sound from outside
in case of a closed space (for example, the six-face visiocube - see further on).
However, setting the correct tension of the flexible screens is difficult because it
involves both, obtaining a surface that is as perfectly flat as possible and restricting
the tension so as not to damage the screen cloth. An incorrect tension and positioning
of screen will lead to frequent tears in the cloth. Besides, considering the surfaces used
(about 10m 2 on average) and the inherent elasticity of the screens, it is impossible to
guarantee perfect flatness of the projection surface. This creates waves on the screens
and thereby distortions of the objects displayed with each air movement (fast move-
ments of a user, slamming of doors, etc.). The rigid screens are a lot more difficult
to carry and since they are not elastic they require accurate positioning systems. On
the other hand, they do not require a tension system, which simplifies maintaining
them in position once they are installed. The shape defects become almost negligible
in comparison with the flexible screens (only a few millimetres in terms of flatness).
Rigid screens thus guarantee a projection surface that is fixed in terms of time, position
and shape. In any case, positioning of the screens has to be accurate enough so that
no gap can be seen in the connections between the contiguous screens. Moreover, the
screens should diffuse the light uniformly on the entire surface, so as to avoid creating
a “hot spot'' in front of the user (see figure 11.6). If need be, it will be necessary to use
screens storing the characteristics of the projected light, for example, its polarisation if
a passive stereoscopic system is used. To retain the polarisation of light in direct pro-
jection, it will be necessary to use metal screens that are fragile and thus not suitable
for consumer products. Stereoscopic flat screens
Stereoscopic flat screens, developed frommonoscopic flat screens of a television, a new
technology, which is less bulky than the video projection technology, is coming in the
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