

@scribus Nonono. Our brain just gets 2 images, both 2d, together with the information of how much the iris has to focus, that gives our brain the illusion that something is far away or near ( because you combine it with knowledge of how things usually are. Which can really work to your detriment in things like http://rainbowdash.net/url/875173 or https://youtu.be/A4QcyW-qTUg?t=31 )
Optical tricks were actually used in Lord of the Rings quite a bit so they wouldn't have to make use of vertically challenged people much.
But... That is not 3D ! That is just using 2D information filtered through both memories and something you could phraise as 'biological trigonometry'
3D vision would actually be something like looking around a tree, while not moving your head.
So some would call what we have to be 2,5 D ( since we can sense distance with 2D input ). However then video games raise their head and go "EXCUSE ME !!! I am 2,5 D !!!" and muddy the whole issue.