🚀 go-pugleaf

I saw the most *amazing* "3D" black and white photocopy of an 
advertisement by PENTICA.  It looked like a random patern of squiggles in
a box with 2 large black dots above.  When you shift the focus of your eyes
to make the 2 dots overlap, this flat XEROX'd picture turns 3D.  It's
like you're looking through a window to a picture about 1 foot below the
paper with letters and numbers at various heights above the picture.

Does anyone know how this was done?  Is there PC software that will let 
you build these and print them on a laser printer?  Is there a collection of
these?  Who did the theory and development?  Does it require more resolution
than exists on a VGA display?  IS there a dynamic/moving version?

I requested more information from PENTICA, but I don't expect a very 
detailed reply.