Chapter 6, psych
Terms
undefined, object
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- Realism
- there is a real world
- Positivists
- only have your sense so the world might be a hallucination
- Geometry of the world:
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-Euclidean in real world
-non-Euclidean in retinal image (2D, curved retina) - Binocular summation
- more likely to see a stimulus because you have two eyes instead of one
- Binocular disparity
- the difference between the two retinal images of the same object; allows us to see 3D (basis for stereopsis)
- stereopsis
- binocular perception of depth
- Monocular cue to 3D space
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1. Occlusion
2. Size and position
3. Aerial Perspective
4. Linear Perspective
5. Motion Cues
6. Accommodation and Convergence - Occlusion
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Object obstruction part of another object is percieved to be closer.
-nonmetric depth cue - relative size
- comparison of size between items without knowing the absolute size of either one (smaller objects seem farther away) (metric)
- texture gradient
- items that change size across the image will appear to form a surface in depth
- relative height
- Objects at different distances form the viewer on the ground plane will form images at different heights in the retinal image. Objects farther away will be formed in the higher visual field (because retinal image is inverted)(metric).
- familiar size
- depth cue based on the known size of something
- relative metrical depth cues
- does not tell us the exact distance to an object or between objects (ex. Relative size and height)
- absolute metrical depth cues
- provides absolute information about the distance the third dimension
- Aerial Perspective
- haze/aerial perspective: light is scattered by the atmosphere and more light is scattered when you look through more atmosphere. The more distant an object is the fainter and less distinct it is.
- Linear Perspective
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-lines that are parallel in the 3D world will appear to converge in a 2D image.
-except when the parallel lines lie in a plane that is parallel to the plane of the 2D image (closed door)
-relative metrical depth cue (not absolute) - Vanishing point
- the apparent point at which parallel lines receding in depth converge
- motion parallax
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-The geometric information obtained from an eye in two different positions at two different times is similar to the information from two eyes in different positions in the head at the same time.
-when your eye moves, objects that are closer to you shift positions more than objects that are farther away when you change your viewpoint (train example)
-head has to move, not just your eyes - accommodation
- lens gets fatter as you direct your gaze toward nearer objects.
- convergence
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eyes rotate inward to focus on something closer
-the more you have to converge the more you lens has to bulge to focus on the object
-absolute metric cue - divergence
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-eyes rotate outward to focus on something farther away
-absolute metric cue - Corresponding retinal points
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-positions that are equidistant from and on the same side as the fovea (crayon example)
-two foveas are also corresponding points - Vieth-Muller circle
- an imaginary circle that runs through the two eyeballs and the object on which a person is fixated on
- horopter
- surface of zero disparity; objects place on that imaginary surface will form images on corresponding retinal locations.
- diplopia
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Objects significantly closer or farther away from the surface of zero disparity will form images on decidedly no corresponding points in the two ey
-see two images - Panum’s fusional area
- region of space in front of and behind the horopter within which binocular single vision is possible
- Crossed disparity
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-in front of horopter
-image reversed - Uncrossed disparity
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-behind horopter
-image not reversed - Steroscopes
- Present different imag to each eye to create single 3D image
- Steroscopic correspondence problem
- problem of figuring out which bit of image in our eye should be matched to which bit of image in the other
- Uniqueness constraint
- a feature in the world will be represented exactly once in each retinal image.
- Continuity constraint
- except at the edges of objects, neighboring points in the world lie at similar distances from the viewer
- absolute disparity
- a difference in the actual retinal coordinates in the left and right eyes of the image of a feature in the visual scene
- relative disparity
- the difference in absolute disparities of two elements in the visual scene
- Binocular rivalry
- the competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the eye eyes
- Bayesian approach
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prior knowledge would influence your estimates of the probability of a current event
-P(Sx|I)=P(Sx) x P(I|Sx) - Ponzo illusion/ Miller line illusion
- over interpreted the depth cues; objects that were the same size in the 2D image would represent objects of different sizes in a 3D image (railroad person example)