Depth Cues & Perception in Multimedia: Psychological & Physiological Factors at NC State, Study notes of Psychology

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Depth Cues

• Psychological
• Physiological

Psychological Depth Cues

• Linear perspective

Size of the image of an object on the retina changes in inverse proportion to its change in distance.

Psychological Depth Cues

• Aerial perspective

Objects further away tend to become less distance, cloudy or hazy.

Psychological Depth Cues

• Interposition

One object occludes, hides or overlaps another.

Psychological Depth Cues

• Color

Fluids in the eye cause refraction. Reds appear closer than blues. Bright objects appear closer than dull ones.

(chromostereopsis)

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Physiological Depth Cues

• Accomodation

Change in focal length of the lens due to a change in tension from the ciliary muscle.

Near object

Far object

Physiological Depth Cues

• Motion parallax

As an observer moves, nearby objects appear to move rapidly while far objects appear to move more slowly.

Physiological Depth Cues

• Binocular Disparity (Stereopsis)

Difference in the images projected on the left and right eyes when viewing a 3D scene. Left Right

Depth Cues

• Stereo Blindness

Approximately 10% of the population cannot see the depth in stereo images.

Emmert's Law

• Size constancy

The ratio of perceived size to perceived distance is constant for a given visual angle.

Given the same retinal angle, B is perceived as smaller than A because B is perceived as closer than A

A

B

Emmert's Law

• The moral:

If you are going to have objects moving around in three dimensions in stereo, make sure they obey the laws of linear perspective.