Rémi Arnaud (remi++at++remi.asd.sgi.com)
Tue, 4 Mar 1997 12:50:59 -0800 (PST)
It was not mentioned by Y.Kanou. Is it for a NVG simulation ? In that
case you certainly can have some time between a color display and the
switch to a monochrome display. So It can be done by having a Monochrome
database as adviced by a previouspost.
The #1 problem in NVG simulation is to get a low level luminance, with a
lot of contrast. If you reduce the luminance by changes in the image
generator you end up using only a few bits of the DAC's and have a
poor output signal with not enough contrast.
One posibility is to keep the maximum luminance in the Image Generator,
so you have a good signal with a lot of resolution, and to add a luminance
information to the projector. Now, the display technology has the same
problem, so to have a good result a solution is to add a filter on the
green tube that reduce the global luminance after the projector.
Anybody has more idea on that subject ?
>
> The stimulation approach involves the use of actual night vision
> goggles where the visual display would emit light that would
> best cause the NVG output to resemble what one would see in the
> real aircraft at night. A somwhat traditional hack includes
> tweaking the color tables and the gamma correction curves.
> Unfortunately current display technology doesn't really
> approximate the night sky terribly well.
See the above comment.
>
> The simulation might use what amounts to viewing the display
> through two toilet paper tubes where the displayed image is
> monocrome green and NVG effects such as noise, blooming, halos,
> automatic gain control in shadowed regions, etc.
I don' know what is a toilet paper tube ?
Note that if you use real NVG in the simulation, you do not have
to simulate the noise, as the noise is produce by the NVG itself. Same
thing for the halos, AGC ...
>
> Just off the top of my head, Performer issues in NVG would
> include:
>
> (1) A culling volume larger than the viewing volume because
> light sources can have a significant effect on the scene
> illumination.
pfLightSource are not culled by the viewing frustrum, and are
applied to the whole scene. So why would you need a larger
culling field of view?
> (2) An Isector from the eyepoint to the moon and other
> significant light sources to see if the light sources are
> occluded by the terrain.
If the sun is not here, then the moon is a significant source of light;
and replace the sun in the global illumination usual mechanism. There
is no need for a isector ?
> (3) If NVGs are simulated, noise injestion could be accomplished
> throug glDrawPixels, I suppose.
See above about noise.
>
> My .02 worth.
>
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