James Trudeau writes:

>  Nonsense?  Beg yer pardon, you and I paid a herd of $$$ for this
>  nonsense.  I feel it is worthwhile and much appreciate your efforts
>  in dealing with stuff I do not and never will understand.  Wear it
>  proudly and keep it coming.

No, you're absolutely right, Jim. None of this is nonsense. I only used the
word defensively because this is so off-topic of the purpose of this list.

If any of you have the time to go hunt up some cellophane, as I suggested in
the previous posting, the stereo images are truly worth looking at. They come
as close to walking on the surface of Mars as you can get, shy of actually
being there.

Stereo images are produced by creating some display mechanism that separates
the information held in a single image into two separate channels, one for
each eye. The mechanism used in these web-based images is red-cyan
coloration. Red is the precise complement to cyan on the color wheel (180
degrees separated in hue angle), thus cyan images will appear black to the
red filter and vice versa.

The red and blue cellophane that I earlier suggested isn't exactly right. The
red is dead on, but the blue is too blue. A slightly greener shade would be
better. Nonetheless, it works well enough to be really quite impressed.

There are two other methods of creating 3-D images. One is through the use of
horizontally and vertically polarizing filters, but this method requires the
use of two separate projectors (Kodak slide projectors, etc.). Each projector
has a matching polarizing filter on its lens to the ones that you have on
your eyes. This method allows the projection of color 3-D images.

By great fortune, Valerie, my wife, and I happened to be at a meeting in
Denver in August of 1976, a month after Viking I landed at Chryse Planitia.
In the month since the landing, JPL had just had enough time to create color
3-D images of the Viking I site -- and they flew the
absolutely-hot-off-of-the-press images every day to Denver so that they could
be interpreted on-the-fly by the Viking planetary group.

Those images were wall sized and better processed than these -- but they gave
you a splitting headache. The angles weren't quite right. And you were
looking through eyes that were a meter apart on the Viking lander.
Nonetheless, I and everyone else felt as if they had actually walked across
the surface of Mars -- and it's something I remember as if it were yesterday.
There was a great deal of joy and excitement in the room.

A second method of creating 3-D images is through the use of synchronized
shutters in a pair of glasses. If a CRT screen can be made to present images
greater than 30 frames per second, where every other frame is the left image
and the other the right, synchronized with the glasses' shutters, the eye's
persistence of vision will blend the two images into a 3-D view. This method
also allows full color stereo images -- and this the method being used by the
rover drivers at JPL.

Color information can be put into the red-cyan method, but it doesn't work
nearly so well as the other two. Black and white is better for the stereo
technique that we're forced to use on a PC screen connected to a web page.

All of these display methods will give you a headache, so don't be too
surprised or too disappointed at that. But the images are worth taking a look
at.

Wirt Atmar


BTW: I created a pair of red-cyan glasses, just like the ones that you used
to get at the old 3-D movies, by disassembling a UPS overnight letter. The
cardboard they use is quite tough, but still flexible enough to form a good
90 degree bend. The longest diagonal distance from corner to corner is just
long enough to create the front surface of the glasses and the two side
pieces that attach to your ears.

High-tech, just like gold, is where you find it :-).