Lecture 6 - Depth Perception Flashcards
Why is 3D perception important?
Vital for interacting w/ world + recognising objects
What is the inverse problem?
Any retinal image consistent w/ infinitely many possible configurations of world
What are binocular cues?
Binocular disparity (brain processes 2 retinal images from each eye + know 3D)
What are motion cues?
Motion parallax (as we move images on retina moves at different rates)
Kinetic depth (when objects move relative to us)
What are pictorial cues?
Texture, elevation, relative size, perspective, shading, occlusion
What are oculomotor cues?
Convergence, accommodation
What is problem if we have so many diff depth cues?
Many cues ambiguous – 2D image compatible w/ infinite 3D worlds
Pictorial cues particularly ambiguous
How do we overcome ambiguity?
Using prior knowledge/assumptions to interpret image
Assumptions gained through knowledge/experience of physical properties of world
Type of top-down processing + supports constructivist approach to vision
What assumptions do we make about the world?
Perspective: Assumption that lines in the world tend to be parallel
Shading: Assumption that light comes from above
Elevation: Assumption that objects rest on a ground plane
Example of a perceptual error?
Ames Room: assumes lines are parallel/perpendicular at right angles but room has slanted back wall and person in right much closer to observer than left
Footprint/ammonite looks convex (hill) b/c we assume light comes from above but is concave b/c light is coming from below (just need to flip the image)
What is multi-cue perception?
Real world scenes have multiple cues present, cues need to be integrated to achieve single unified percept
(integration helps overcome problems of reliability/ambiguity/conflict)
What are the three types of integration?
Compromise, Dominance, Interaction
What is compromise?
Take average but consider how reliable each friend is (eg. Bill is better?)
When two sources of info conflicting brain will try to find compromise
What did Young et al. study?
2 cues in conflict in cylinder, participants perceived shape biased towards more reliable cue (texture vs motion)
What is dominance?
Only trust one and ignore other (Ames room)
Two cues define very diff shapes/depths brain may choose to ignore one in preference for the other
