Depth Perception: Cues and Mechanisms, Schemes and Mind Maps of Psychology

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Chapter 8: Perceiving Depth and Size

Cues to Depth Perception

•^

Oculomotor

• cues based on sensing the position of the eyes and muscle tension

Convergence

• knowing the inward movement of the eyes when we focus

on nearby objects^ 2.

Accommodation

• feedback from changing the focus of lens.

Occlusion

• when one object partially covers another

Relative height

• objects that are higher in the field of vision are

more distant

Pictorial Cues

Pictorial Cues

•^

Relative size

• when objects are equal size, the closer one will take up more of

your visual field

-^

Perspective convergence

• parallel lines appear to come together in the

distance

-^

Familiar size

• distance information based on our knowledge of object size

Texture gradient

• equally spaced elements are more closely packed as

distance increases

Pictorial Cues

Shadows

• can help indicate distance

Pictorial Cues

Name the pictorial cues in this scene

atmospheric perspectivetexture gradientshadows

1.^

Occlusion

2.^

Relative height

3.^

Relative size (familiar size)

4.^

Cast shadows

5.^

Atmospheric perspective

6.^

Perspective convergence

7.^

Texture gradient

Cestello Annunciation

Name the pictorial cues in this scene^ by Sandro Botticelli, circa 1489-1490.

Binocular Depth Information

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Binocular disparity - difference in images between the two eyes

Point of fixation

Points away from fixation will usually

have

binocular disparity

:

the point will project to different places

on the two retinas.

In this example, the disparity on the left is smaller than the disparity on the right.

Binocular disparity For objects straight in front of you, if it’s in front of fixation:

crossed disparity

behind fixation:

uncrossed disparity

Once you’re fixating, the relative positions of other locations on the two retinas

can serve as a cue to depth.

It’s a little more complicated for objects that aren’t directly in front of you.

The horopter

• imaginary circle that passes through the point of focus.

Objects on the horopter fall on corresponding points on the retina

All objects on the horoptor have neither

crossed, nor uncrossed disparity

Two images of a stereoscopic photograph. The difference between the two images, such as the distancesbetween the front cactus and the window in the two views, creates retinal disparity. This creates aperception of depth when (a) the left image is viewed by the left eye and (b) the right image is viewed by theright eye.

-^

Stereopsis

• depth information provided by binocular disparity

–^

Stereoscope uses two pictures from slightly different viewpoints

-^

3-D movies use the same principle and viewers wear glasses to see the effect

Random-dot stereogram has two identical patterns with one shifted to the right