Originally Posted by Haze_hellivo
You been watching The Matrix too many times. When you close one eye you loose depth perception and cant calculate distances very well.
exactly - which is why your brain makes it up.
I'm sure everyone's done the trick where you put 2 crosses on a piece of plain paper about 4 inches apart, then close your left eye, stare at the left hand cross and move the paper back and forth slowly - the right cross will disappear at a certain distance, but you can see it with the paper either closer or further away.
This is because your brain guesses what's in the blank spot where the optical nerve leaves your eyeball (you cannot 'see' anything here - but this usually isn't an issue if you have 2 eyes because the blind spots don't conicide). As there is plain paper all around the blank spot it fills in the blank with that same colour - missing the fact that the cross is there at all.
The brain does the same thing with depth - it guesses what's there to try and give you the best picture it can.