PA wk 6- Depth perception Flashcards
the inverse problem with retinal images
any retinal image is consitant with infinite possible configurations of the world
Oculomotor cues
cues that depend on our ability to sense the position of our eyes and tension in our eye muscles.
e.g. eyes have to converge to look at objects closer to us.
- accommodation cue. lens in eye changes shape to focus image. Will be fatter if closer, thinner further away.
pictorial cues
monocular cues - cues that can be depicted in a still picture
e.g.
- texture
- elevation
- relative size
- perspective
- shading
- occlusion
Motion-produced cues
cues that depend on movement of observer or of objects in environment
e.g. motion parallax (car window, movement in opposite directions depending on distance
- kinetic depth. part of surface closer will move faster
Binocular disparity
a cue that depends on fact that diff eyes produce diff images.
The fact that an object can look the same size regardless of changing retinal image size is referred to as
size constancy
ambiguity in depth percpetion
many 3D cues (particularly pictorial) are ambiguous
- can overcome this via prior knowledge, or assumptions to interpret knowledge
- gained thru experience
- = top down
ambiguity in shading
light tends to come from above
ambiguity in elevation
objects rest on ground plane.
and so those higher up are further away, those lower down are closer
multi cue perception
Real-world scenes have multiple cues present
Cues must be integrated to achieve a single unified percept
Integration helps to overcome problems of:
Reliability
Ambiguity
Conflict
3 types of integration
- Compromise (take an average, but weighted toward the one u trust)
- Dominance (one seems incorrect so go with other)
- Interaction (both info source sort of say same thing differently)
how did young et al study multi cues
study 1
asked whether cylinder was stretch, circular, flattened.
gave 2 cues, texture and motion
atrificially generated a flattened texture cue with a stretched motion cue.
Found, ppl compromised between the cues.
how did young et al study multi cues
study 2
they made 1 cue less reliable (by making the texture dodgy).
Perceived the motion cue to be more dominant in determining stretched.
also worked in opposite direction
dominance summary
when conflict between 2 cues is too great, the brain will chose one cue and ignore other.
e.g. elevation vs relative size of hot air baloons
Interaction example
if take texture of cylinder alone, can seem concave or convex.
Binocular disparity can disambiguate
order of integration
interaction, (cues disambiguate others)
then compromise (then these cues come together)
