Depth Perception:

Depth perception is the ability to see the world in three dimensions and to perceive distance. Although this ability may seem simple, depth perception is remarkable when you consider that the images projected on each retina are two-dimensional. From these flat images, we construct a vivid three-dimensional world.

To perceive depth, we depend on two main sources of information:

1.  Binocular disparity

2.  Monocular cues

Binocular disparity:

Perhaps the most important perceptual cues of distance and depth depend on so-called binocular disparity. Because our eyes are spaced apart, the left and right retinas receive slightly different images. This difference in the left and right images is called binocular disparity. The brain integrates these two images into a single three-dimensional image, allowing us to perceive depth and distance. The phenomenon of binocular disparity functions primarily in near space because with objects at considerable distances from the viewer the angular difference between the two retinal images diminishes.

Monocular cues:

Monocular cues are cues to depth that are effective when viewed with only one eye. Although there are many kinds of monocular cues, the most important are interposition, atmospheric perspective, texture gradient, linear perspective, size cues, height cues, and motion parallax.

Interposition:

Probably the most important monocular cue is interposition, or overlap. When one object overlaps or partly blocks our view of another object, we judge the covered object as being farther away from us as see in Fig .24c.

Atmospheric Perspective:

The air contains microscopic particles of dust and moisture that make distant objects look hazy or blurry. This effect is called atmospheric perspective, and we use it to judge distance.

Texture Gradient:

A texture gradient arises whenever we view a surface from an angle, rather than directly from above. The texture becomes denser and less detailed as the surface recedes into the background, and this information helps us to judge depth.