Principle of 3D imaging

We have two eyes separating about 6cm (we call it binacular parallax). This is the reason why we can see in 3D. When we look at a object, the left eye and right eye see a pair of little different images. The brain calculates the depth information with the ewo different images and get a real 3D image.

When you look at an object with both eyes, each eye sees it from a little bit different angle. Your brain puts the different-angled images from each eye together allowing you to see in stereo (we call this depth perception).