Depth Perception

Question 1

What are the three major groupings of depth cues?

Answer 1

Oculomotor
-Based on feedback from eye muscles
Monocular
-One eye
Binocular
-Requries two eyes

Question 2

Definte the two oculomotor cues. How effective are they?

Answer 2

• Convergence
• Based on feedback from the muscles that control the movement of the eyes
• The smaller the angle between the fixated object and the two eyes, the more distant the object is
• Accomodation
• Based on feedback from muscles that control the lens
• The process by which the lens of the eye changes shape to bring objects at different distances into focus on the retina

Convergence and accomodation are effective up to about one meter. Convergence is more effective.

Question 3

Define the eight monocular pictorial cues.

Answer 3

-Occlusion
Objects that block another object are closer.
-Relative Height
Objects that appear closer to the horizon are further
Cast Shadows
-“Light-From-Above” heuristic is used to generate information about depth from shadows
-Relative Size
If two objects are the same physical size, the object that takes up a smaller area on the retina will be perceived as further
-Familiar Size
Objects of known sizes will be perceived at an appropriate distance to account for their perceived size
-Atmospheric Perspective
The greater the haze, the further the object
-Linear Perspective
Straight lines that recede into the distance appear to gradually converge
Texture Gradient
Objects at a distance appear more densely packed

Question 4

Define the monocular movement produced cues.

Answer 4

Motion Parallax
Objects further than fixation point appear to move in the same direction as you whereas objects closer appear to move in the opposite direction

Accretion
Moving past two objects, parts of the back object are uncovered by the front

Deletion
Moving past two objects, parts of the back object are covered by the front.

Question 5

What is Stereopsis?

Answer 5

Stereopsis is the perception of depth that is derived from retinal disparity

Question 6

Give properities of the horopter.

Answer 6

• Goes through the fixation point
• Almost circular
• Objects on the horopter fall on corresponding retinal points
• Other objects fall on disparate retinal points
• Objects within horopter have crossed disparity
• Objects beyond horopter have uncrossed disparity

Question 7

What is the signficance of a random dot stereogram

Answer 7

• Contains no depth cues

- Prove that retinal disparity produces stereopsis

Question 8

What did Blake & Hirsch(1975) do to investigate disparity detectors, and what did it prove.

Answer 8

• Raised cats for 6 months
• Vision was alternated between each eye every other day
• Adult cats had few binocular neurons and could not use binocular disparity to perceive depth.

-Proved the link between the perception of depth from binocular disparity cues and the prescence of disparity detectors in the visual pathways.

Question 9

What is the Correspondence Problem?

Answer 9

To use binocular disparity, the visual system needs to match points on one retinal image with similar points on the other retinal image.