Fun With Stereoscopic Forced Perspective

Daniel Briggs and I were discussing this morning the coolness of parallax scrolling, which quickly led into even geekier notions of dual tandemized VFX interfaces that had pseudo 3D icons.
Have you ever looked through a chain-link fence at something and then the fence pattern lines up with itself and you get this weird trippy false-depth thing that happens?
No, just me?  How about this one: have you ever put your two pointer fingers together in front of your face and looked past them and observed the mysterious floating finger sausage?

www.coolopticalillusions.com

It's not a new trick to take pictures from two angles at a common vanishing point and mash them together to reveal depth.  Usually it's with the aid of some apparatus (like a Viewmaster!).  But if you do it enough, in your undergraduate remote sensing courses for instance, just before you go permanently wall-eyed you can get so that you don't need the stereoscope glasses doodads.  Are you able to focus your eyes "behind" the monitor so that these dual images below slide together into one?

With a skew transform added to the standard extrusion icon, reversed from one panel to the other, we can set up a parallax view.  Do these map extrusion icons reach out and grab you?  Or at least poke you in the eye?

Here's one where instead of forcing perspective using map icons, I've skewed the map, itself, so that the effect is that of looking at a laid-down map where Long Beach is closest in the foreground and Downey is back in the distance.

What sort of bedevilment might happen if I combined the two tactics and make a magic eye map that forces perspective of the basemap AND the map icons?  If you can befuddle your eyes enough to register a magic merged map in the middle, the pseudo- 3D effect is particularly convincing.  But it gives me a headache after a while.

P.S. Randall Munroe of the great XKCD.com has a great comic about stereoscopy with webcams, a smartphone, thick reading glasses, a formidable imagination, and a beautiful world: http://xkcd.com/941/