Re: [photo-3d] stereo projection dome

["John A. Rupkalvis" <stereoscope@xxxxxxxxxxxxx>]

Here is a copy of the e-mail I had sent to Douglas Noble:

Interesting project.

Coincidentally, there are a few similarities to a project that I did nearly
30 years ago for the School of Architecture at the University of Minnesota!

That project involved stereoscopic projection of stereo slides on a 70 foot
diameter spherical screen.  This screen was actually a balloon, inflated
inside of the School's auditorium (it was summertime, and the lecture hall
was not being used).

There was a tunnel attached to the balloon (sort of like an igloo entrance),
with a doorway flap at each end.  This acted as double air trap, so that
people could enter and leave without deflating the balloon.  It was kept
inflated at low pressure just with a single two foot portable fan.  It took
a long time to inflate, but once inflated, it stayed there.  A maximum of
about two dozen people could watch the show at one time.

Rather than putting chairs inside, we just covered the bottom with cushions.
That way, people could sit, recline, whatever, and move around to view
different parts of the sphere (projection was on all sides and the top).

Although the plastic that the balloon was made of was non-depolarizing on
axis, it tended to depolarize at an angle.  Although I experimented with
polarizers, I ended up using anaglyph projection, so that a large area of
the surface could be covered using Ektagraphics fitted with extreme wide
angle projection lenses.

Three of the projection "heads" (two Ektagraphics in each "head") were
inside the balloon, and nine on the outside (the material was translucent).
The slides in the exterior projectors had to be "flopped" left-for-right so
that they would read right when viewed from the inside.

All in all, it was quite successful, in that we always had more people
wanting to see it than there was room to accommodate.  Especially
surprising, since there was no budget for advertising, and people would hear
about it only by word-of-mouth.

Today, this would be somewhat easier to accomplish, since LCD shutter
glasses could be used, and there would be no polarization problems.  This
would be much better than the anaglyph.

I would be interested in helping you with your dome project, if time
permits.  My problem right now is that I do not have the time or financial
situation where I can afford to donate time to anything that doesn't pay the
rent.  I would like to, but it just isn't possible right now.  I must focus
on priorities (survival).

Anyway, I wish you the best in your project.   I am going to be out of the
country for from two to six weeks (depending on how things work out) working
on a 3-D project that pays (marginal, but something is better than nothing).
I plan to leave Tuesday or Wednesday.  In the mean time, let me know if
anything makes sense.

JR