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25 Cards in this Set
- Front
- Back
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depth vs. distance
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depth: nonmetric relative position from observer (nearer/farther)
distance: metric absolute position given using some kind of metric or scale (may be body scaled) |
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motion parallax
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when your eyes move, objects closer to you shift position more than objects farther away when you change your viewpoint (only works when head moves, not when eyes move)
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optical expansion/contraction
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when an object approaches, its image expands
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accretion/deletion of texture
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when a surface moves relative to another, the nearer surface progressively occludes background texture on the further surface
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binocular summation
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performance on many tasks better with both eyes than with either eye alone
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stereopsis
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the ability to use binocular disparity as a cue to depth
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horopter
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points in space which are imaged on corresponding points in the two retinas, that is, on anatomically identical points
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crossed disparity
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object changing in front of the horopter (and in front of the object being focused)
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uncrossed disparity
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object changing behind the horopter (behind the point being fixated)
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accommodation
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changes in shape of the lens to achieve focused images at varying distances (lens gets fatter as we direct our gaze toward nearer objects)
(accommodation may provide distance information via unconscious sensing of the muscular movements in ciliary muscles) |
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convergence
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turning of the eyes to a particular point in the center of fixation
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accommodation and convergence: when is it useful?
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2 meters or less (near space)
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accommodation and convergence: metric or nonmetric?
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metric, potentially
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assumed physical equality
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visual system operates as if it assumes that things whose projections to the retina are different are actually similar in the world
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linear perspective
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based on rules that determine how lines in 3D space are projected onto a 2D image
lines that are parallel in 3D will converge in a 2D image towards the vanishing point |
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relative size
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smaller=farther away
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relative height
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for objects on the ground plane, objects that are more distant are higher in the visual field
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aerial perspective
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distant objects are subject to more scatter and appear fainter and less distinct (bluish)
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is occlusion metric or nonmetric?
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nonmetric- gives information about depth order, not depth magnitude
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out of all the depth cues, what are the most ecologically valid?
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stereoscopic and kinematic cues
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of all the depth cues, what is the least ecologically valid?
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pictorial
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size algorithm
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S=Ds/d
S=real size D=viewing distance gotten through distance perception s=projective size on the retina d=depth of the eyeball (constant) |
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how do you eliminate stereopsis?
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view from one eye
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eliminate accommodation?
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artificial pupil
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eliminate texture?
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cover surfaces with draperies
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