See if this helps: You know how the moon "librates"? Rocks a bit during it's orbit...first we see a little bit further around the limb on one side, then a few days or weeks later, we see a little bit further around the other limb? Stereo vision is like seeing both libration extremes simultaneously; with all 3-dimensional objects. It's not an illusion; it's witchcraft. ;) Chuck __________________________________________________ Do You Yahoo!? LAUNCH - Your Yahoo! Music Experience http://launch.yahoo.com