The eye (i.e., the retina) receives sensory input in only two dimensions (length and width). It is therefore the brain’s task to make these cues into a three-dimensional perception.
This task is conducted by the use of monocular (one eye) depth cues and binocular (both eyes) depth cues. Here is a list of the depth cues that the brain uses to make the work seem three-dimensional (3D).
Monocular depth cues:
- Patterns of light: Different patterns of light can be used to illustrate depth (e.g., in painting)
- Shadow: Shadows can be used to illustrate depth (e.g., in a painting)
- Linear perspecive: Parallel lines converge as they become more distant
- Interposition: Nearby objects may cut off parts of our field of vision
- Height in the horizon: The objects that are distant seem closer to the horizon
- Texture: The texture of an objects appears sharper when it approaches
- Clarity: We see nearby objects more clearly
Binocular depth cues:
- Binocular disparity: Each eye sees a slightly different image
- Convergence: The muscles of the eye turns the eye inward to view close object