P3D Re: "impossible" images in stereo

[Gabriel Jacob <jacob@xxxxxxxxxxxxxx>]

John Roberts writes:
>The 2D "impossible images" take advantages of the fact that there's only
>one view, in order to fool the human perceptual system in an interesting
>way. So - can anyone think of stereo (2-view) images that take advantage
>of the fact that there are only two views, to fool the human perceptual
>system in interesting ways?

I'm not sure if this fits the bill, but it does fool the senses in an
interesting way. I don't take credit for it, which I found in some
publication (forget exactly where) sometime ago.


In the first ascii stereo pair (use fixed pitch fonts to see this 
correctly), you'll see the ball (o) behind the window, if your 
parallel viewing and above the window if cross-eyed viewing.
                  _____________________ _____________________
                 |                     |                     |
                 |                     |                     |
                 |         o           |           o         |
                 |                     |                     |
                 |_____________________|_____________________|
                                                      
In the next ascii stereo pair, you'll see the ball above the window,
if your parallel-viewing and behind if cross-eyed viewing.
                  _____________________ _____________________
    
                 |                     |                     |
                 |                     |                     |
                 |           o         |         o           |
                 |                     |                     |
                 |_____________________|_____________________|
                                                      
Now here is where it gets interesting. If you put the both balls in
the same image, you would expect one to be behind and the other to
be above the window. Problem is they would BOTH now be AT the 
window, regardless if you freeview parallel or cross-eyed!
                  _____________________ _____________________
                    
                 |                     |                     |
                 |                     |                     |
                 |         o o         |         o o         |
                 |                     |                     |
                 |_____________________|_____________________|

I'll leave it up to you all, to figure out why!

Gabriel