The real world is three-dimensional yet most graphical representations are two-dimensional. 2D graphics depict the width and height dimensions of objects but the depth dimension is missing. Graphics such as this are flat and can convey only a limited amount of information. In 3D graphics we start to add the impression of depth using a variety of 'cues' such as light and shade, cast shadows and perspective.

We can also create 3D by viewing graphics in stereo; that is, viewing two slightly different views of the same scene with two eyes. We see the real world in stereo because we have two eyes and with each eye we see a slightly different view of the world (try closing one eye, and then the other, and then alternate between eyes). The difference in view observed is used by the brain to calculate distance of objects relative to the eyes. In fact, this difference (called disparity) is proportional to the distance of the objects from where the eye fixates (focuses attention) and has a sign (+ or -) dependent on whether the object is in front or behind the fixation point.

In the very succesful film Avatar the scenes were shot using two cameras (or computer generated pictures ). The views from the two cameras are superimposed and when viewed with stereo glasses the scene appears in 3D because the disparities resulting from the two camera setup are interpreted by the brain as depth differences.