: Has anyone seen hallusions?  You can buy a poster of them and it looks like a simple dot pattern
: when you first look at it but if you focus behind it you see a 3d picture.  I'm looking for
: a program that generates these pictures.  There's a company in Texas that makes them but I 
: doubt if they're giving the program away.  Any help would be appreciated. 
: 
There is a program included with the book "Virtual Reality Playhouse" which
will let you generate these pictures.  It's not a very powerful program but
it does an acceptable job for experimentation purposes.