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psych 330 > 16-17. depth 1&2 > Flashcards

16-17. depth 1&2 Flashcards

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1
Q

Many to one representation meaning?

A

There are many different 3D scenes that can produce the exact same retinal image

  • a big balloon far away
  • a small balloon really close
  • a medium balloon in the middle
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2
Q

Retinal size depends on…? (2 things)

A
  1. size of object
  2. distance to object
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3
Q

Ways to divide depth cues?
(3 levels of tree diagram)

A
  • oculomotor vs retinal image
  • monocular vs binocular (disparity)
  • mono: static vs dynamic
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4
Q

Oculomotor cues meaning? 2 types? Problem?

A
  • cues based on feedback from muscles controlling shape of lens and position of eyes
  • neither are very precise or super helpful
  1. accommodation
  2. convergence
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5
Q

2 types of monocular cues (and meaning) ?

A
  • only need one eye to provide depth information
  • static (doesn’t need motion)
    –> all info is in a picture
  • dynamic (requires motion)
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6
Q

3 types of static cues?

A
  • position based
  • size based
  • lighting based
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7
Q

2 position based cues?

A
  1. partial occlusion
  2. relative height

Position of things relative to each other

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8
Q

4 size based cues?

A
  1. familiar size
  2. relative size
  3. texture gradients
  4. linear perspective

change in size (relative) gives you depth info

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9
Q

3 lighting based cues?

A
  1. atmospheric (aerial) perspective
  2. shading
  3. cast shadows

lighting info = depth info

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10
Q

3 dynamic cues?

A
  1. motion parallax
  2. optic flow
  3. deletion and accretion
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11
Q

Accommodation def? Type? (Problem?)

A

Oculomotor

  • detect change in ciliary muscles to adjust lens to focus on the object
  • VERY limited range (<2m)
  • Even within that range, may still be very imprecise
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12
Q

Convergence def? Type? (Problem?)

A

Oculomotor

  • detect how converged your eyes become to focus on an object
    –> far away = not converged
    –> super close = very converged
  • VERY limited range (<2m)
    –> beyond that, the angle between your eyes changes very little
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13
Q

Partial occlusion def? Type of cue?

A

Monocular - static - position based

If an object partially covers another, you perceive the former (cover-er) as closer than the latter (covered)

*very reliable

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14
Q

Relative height** def? Type of cue?

A

Mono - static - position

An object that is closer to the horizon (or eye level) appears farther away

Think of the beach/inlet scene

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15
Q

Size-distance relation meaning?

A
  • the farther away an object is, the smaller its retinal image
  • RETINAL size decreases proportional to the increase in distance
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16
Q

Familiar size def? Type of cue?

A

mono - static - size

  • use the retinal image size of a familiar object to judge our distance to it
  • we know the retinal image size of familiar objects at familiar locations
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17
Q

Relative size def? Type of cue?

A

mono - static - size

  • if several objects (ex. people) are all about the same physical size, we use RELATIVE size of retinal images to judge distances
  • familiar objects are the same size, but some appear much bigger –> helps judge distance
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18
Q

Texture gradient def? Type of cue?

A

mono - static - size

  • if surface variations or repeated elements of a surface are fairly regular in size and spacing, the retinal image size of these equal-size features decreases as their distance increases
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19
Q

Accelerated texture gradient meaning?

A
  • Adjusting the spacing between repeated elements in a design
  • creates illusion to make a building look longer/taller etc
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20
Q

Linear perspective def? Type of cue?

A

mono - static - size

  • parallel lines appear to converge as they get farther away
21
Q

Atmospheric (aerial) perspective def? Type of cue? (why?)

A

mono - static - lighting

  • parts of the image that are REALLY far away tend to be hazier, blurrier, and a little bluer
  • the farther the distance = more air between you and the object
    –> more light scattered = objects are blurrier
  • only works with large distances
22
Q

Shape from shading def? Type of cue?

A

mono - static - lighting

  • gives information about relative depth / orientation of different parts of the object
  • people very biased to assume light source comes from above
23
Q

What implicit assumption do we make about shading/lighting? Why is it important?

A

That the light source comes from ABOVE!

  • if an object is light on top and shaded on the bottom, (most common) we think its raised above the background
  • if an object is shaded on top and light on the bottom, we think its indented
24
Q

Cast shadows def? Type of cue?

A

mono - static - lighting

  • depth can be signaled by the shadows cast by an object
  • shadows can make you think an object is moving away or staying at the same distance but floating
25
Q

Motion parallax def? Type of cue?

A

mono - dynamic

  • objects appear to move in diff speeds and directions in the retinal image as an observer moves ACROSS a scene
  • things CLOSER move FASTER (and FARTHER)
26
Q

Motion parallax –> how does where you’re looking affect the direction the objects “move”? (Ahead vs middle)

A

If you look straight ahead: all objects move OPPOSITE the direction you move

If you FIXATE on an object in the middle…
- objects closer than fixation move OPPOSITE
- objects further from fixation move SAME direction

27
Q

Optic flow def? Type of cue?

A

mono - dynamic

  • the relative motions of objects and surfaces in the retinal image as the observer moves forward or backward through a scene
  • things closest to you move away from the focus of expansion much more quickly
28
Q

Focus of expansion def?

A
  • The point toward which you’re moving when talking about optic flow
  • everything moves outward from that point
29
Q

Deletion and accretion def? Type of cue?

A

motion - dynamic
- deletion: objects are hidden as they move behind things
- accretion: objects are revealed as they emerge from behind things

30
Q

Stereopsis meaning?

A

The vivid sense of depth arising from the visual system’s processing of the different retinal images in the two eyes

31
Q

Binocular disparity def?

A

A depth cue based on differences in the relative positions of the retinal images of objects in the two eyes

32
Q

Corresponding points def?

A

A point on the left retina and a point on the right retina that would align if they were superimposed

Exs:
- foveas are corresponding
- 2 spots that are both 4mm Left of fovea

33
Q

Non corresponding points def?

A

Any 2 points on L+R retinas that wouldn’t exactly line up

Ex:
- L fovea and 4mm off R fovea

34
Q

Horopter def?

A

An imaginary surface defined by the locations in a scene from which objects would project retinal images at corresponding points

35
Q

3* types of disparity?

A
  1. crossed disparity
  2. uncrossed disparity
  3. zero disparity* (no disparity)
36
Q

Crossed disparity def?

A
  • an object that is closer to you than the horopter has crossed disparity
  • to fixate on it, you’d have to converge your eyes more than they already are
37
Q

Uncrossed disparity def?

A
  • an object farther than the horopter has uncrossed disparity
  • not crossed
38
Q

Zero disparity def?

A
  • an object on the horopter has zero disparity –> NO disparity
  • this applies to the object you’re fixated on and any other objects on the horopter
39
Q

Magnitude of disparity?

A
  • an object closer to the horopter (but not on it) will have LESS disparity than an object farther from the horopter
  • regardless of whether its crossed / uncrossed
    –> (closer/farther to YOU from the horopter)
40
Q

Correspondence problem meaning?

A

how does our brain know that the L retinal image retina was produced by the same object as the R retinal image?

problem of determining whether/which features in one ret. image correspond to the other

41
Q

Stereogram def?

A

Two depictions of a scene that differ in the same way as an observer’s two retinal images of that scene would differ; an observer who simultaneously views one image with one eye and the other image with the other eye (as in a stereoscope) will see a combined image in depth

42
Q

Random dot stereogram def? Important for?

A
  • 2 grids of randomly arranged dots –> identical except for the displacement of a portion in one image relative to the other;
  • view in stereoscope or anaglyph (superimposed)
  • you’ll see a single image with the displaced portion in depth
  • important to determine if object recognition happens before or after matching corresponding parts of retinal image (correspondence problem)
43
Q

Answer to correspondence problem? (What happens first - corr. Match or object recog?)

A
  1. correspondence matching has to happen for binocular disparity
  2. RDS doesn’t contain any objects. But you perceive depth. Therefore, correspondence matching PRECEDES object recognition
44
Q

How does correspondence matching happen in the brain? (2 assumptions)

A
  1. each feature matches only one other feature
  2. visual scenes tend to have smooth and continuous surfaces with relatively few abrupt changes in depth
45
Q

Binocular cells – what are they?

A
  • neural mechanism for binocular disparity
  • neurons that respond to the stimulation of their receptive fields in both eyes simultaneously
46
Q

Binocular cells – how do they work?

A
  • receptive fields for binocular cells are at different corresponding or non-corresponding points
  • different binocular points are tuned to different DISPARITIES (crossed, uncrossed, or zero)
    –> tuned to different magnitudes of disparity
47
Q

Binocular cells – what needs to happen for it to respond?

A
  • both receptive fields (in both eyes) need to be stimulated)
  • these receptive fields are most often non-corresponding
48
Q

Binocular cells – where are they?

A

Have been found all over!
V1, V2, V3
Dorsal (MT) “where/how”
–> reaching/grasp depth perception
Ventral (V4/IT) “what”
–> depth for object shape perception

49
Q

How early is depth information available in visual processing?

A
  • very early!
  • prior to visual search
  • during pre-attentive processing

psych 330 (25 decks)

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