P3D Re: Stereo Window Demonstration

[Bruce Springsteen <bsspringsteen@xxxxxxxxx>]

George, you ARE confused!  Now you can't remember which thing you think
and which one Ron Labbe thinks?  Time for a quiet vacation in Greece
looking out a window...

I too tell people to move their chips out to "push the scene back"
relative to the window in their slides.  And I don't trouble them with the
theoretical error of making convergence changes in the whole scene to deal
with a fixed window - I reason, to paraphrase McKay, "What they don't know
ain't gonna hurt them, for now."  But I only do this because when you are
doing slides, you have no choice in the matter - so I am a hypocrite
perforce, not by design.

But in an animation on the internet, like Larry has (had?) on his site, or
when prints are on hand, or in a situation where you are devising your own
gadgets for demos, why not do it the "right" way and move the window
apertures, leaving the infinity and other separations of the pair intact? 
If you learn the window that way, as I did, you have the actual meaning of
the window position in mind, and can easily discuss how to adjust for the
limits of projection later.  But if you do it the other way round,
conditioning people to think of moving the scene rather than the window,
then how do you undo that concept when the time comes to understand the
real deal?  "Oops, sorry, you weren't really controlling the window
position before, but now I'll tell you haw to do it - honest!"

BTW, I've seen Ernie Rairdin's ingenious sliding stereocard - and someone
described a similar gadget in a recent "Stereoscopy".  Now I guess I have
to invent one where the aperture moves, not the image, huh? ;-)

Bruce
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