6. Depth Perception Flashcards
What is the inverse problem of depth perception?
the retinal image can be caused by numerous possible configurations of the world
What are the 4 main forms of depth cue?
Binocular, motion, pictorial, oculomotor
Binocular disparity occurs because:
a scene falls on different parts of the retina between the two eyes due to the eyes being in different positions.
Binocular disparity is measured in what unit?
Degrees
Binocular disparity is directly proportional to __, and inversely proportional to __
Depth
Squared viewing distance
Motion cues: what is motion parallax?
Motion on the retina caused by our movement relative to other things
Motion cues: what is Kinetic depth?
motion on the retina due to objects moving relative to us. Closer parts of an object will move faster than far parts
Pictorial cues: how does texture indicate depth?
sunflower field analogy: the more texture, the further something is away
Pictorial cues: how does elevation indicate depth?
Things that are lower down tend to be closer to us
Pictorial cues: how does relative size of objects indicate depth?
the bigger something is, the closer it is
Pictorial cues: how does perspective indicate depth?
lines converge as things get further away
Pictorial cues: how does shading indicate depth?
light and dark shading can show convexity or concavity
Pictorial cues: how does occlusion indicate depth?
objects that are occluding/hiding others must be in front (nearer to us)
Oculomotor cues: what is convergence and how does it signal depth?
- eyes bend in when focussing on near object
- have to converge more if object is close, muscles signal this to the visual system
Oculomotor cues: what is accommodation and how does it signal depth?
- lens enables light to be focused on the retina
- lens gets fatter for close objects and thin for far objects through the ciliary muscles, which send signals to brain
What are the problems with depth perception cues? (2)
- the cues are ambiguous
- how are all the different cues combined?
Using prior knowledge and experience of physical properties of the world (top-down processing) can solve which problem of depth perception?
Ambiguity (retinal image could be created by numerous configurations)
In perspective, we use top down assumptions that lines in the world tend to be __?
parallel or perpendicular
In shading, we use what assumption about light in the world?
It comes from above
What assumptions are made about surface textures in depth perception?
They are isotropic (unbiased orientation) and homogeneous (same density across the surface)
What do the assumptions of texture being isotropic and homogeneous allow us to believe?
Changes in texture must be due to the 3D orientation of the object
When using the depth cue of elevation, we assume that objects rest on the __
Ground (due to gravity)
Sometimes, assumptions are not correct leading to perceptual illusions. These assumptions are called:
Erroneous assumptions
Multi-cue integration: what is compromise?
take an average of the information from both cues, but the average will be biased toward the most reliable cue
Multi-cue integration: what is dominance?
trusting one cue and ignoring the other if they are providing very different information
Multi-cue integration: what is interaction?
use of a cue to make another cue less ambiguous
The Ames Room illusion can be explained by which form of multi-cue integration, and how?
Dominance: we choose the invalid cue (perspective) and ignore the correct one (relative size).
Interaction: binocular disparity can disambiguate which pictorial cue?
texture - if something is convex or concave
There is evidence that interaction (cues being disambiguated by less ambiguous cues) occurs before cues being compromised: True or False?
True
Conflict between these types of depth cue can lead to headache, eye strain, and nausea:
Binocular and oculomotor cues
