We introduce the perceptual issues relevant to seeing three dimensions in digital imagery. Technological constraints like limited field-of-view and spatial resolution prevent the display of images that match the real world in all respects. Therefore, only some elements of real world depth perception are utilized when viewing 3D CGI. Depth Cue Theory is the main theory of depth perception. It states that different sources of information, or depth cues, combine to give a viewer the 3D layout of a scene. Alternatively, the Ecological Theory takes a generalized approach to depth perception. It states that the HVS relies on more than the image on the retina; it requires an examination of the entire state of the viewer and their surroundings (i.e., the context of viewing). In this paper, we rely on Depth Cue Theory, although we acknowledge the importance of visual context where appropriate. As seen later, the type of visual environment and the viewer’s task play a significant part in the effectiveness of a 3D VDS. Both theories assert that there are some basic sources of information about 3D layout. These are generally divided into three types: pictorial, coulometer and stereo depth cues. The perceptual process by which these cues combine to form a sense of depth is a complicated and outdebated issue. Different approaches to measuring the ability to perceive depth have also been posited. We discuss these issues with respect to CGI.