Then we have to modify the scene as the viewer moves, so as to retain
the illusion. Maintaining the illusion for multiple viewers would be
a real challenge. Essentially, you'd have to have everyone view a
"4D" world: that's 3D + extra processing.
I think that any illusion generated on a 2D piece of paper, could find
a moving analogue on a 2D computer screen. Proving/disproving this
assertion would be an interesting math problem, and is left to the
reader as an exercise. :-)
Cheers,
Brandon