W8: Depth Perception

Question 1

Define stereopsis and retinal correspondence

Answer 1

perception of depth from binocular disparity (V1)

Corresponding retinal points on each retina receive input from the same point in space

Question 2

Define the horopter and how it’s measured

Answer 2

plane where all locations lie at the same depth as the fixation point

Haplopic method: objects with similar depths fused into binocular percepts; pin moved and noted when seen as double

Midpoint between inner/outer limits of singular vision

Question 3

Describe Panum’s fusional area and 2 instances of retinal disparity

Answer 3

Panum’s: where stimuli are seen as singular/fused

Crossed: Receptive field register in front of horopter/Panum
Uncross: Receptive field register behind horopter/Panum

ODCs form basis of fields

Question 4

Describe stereograms

Answer 4

2 copies of an object further away at the plane of focus

2 photographs of a visual scene with a camera separated appropriately

Question 5

Name 3 modern stereogram approaches

Answer 5

Red-Green Anaglyph: 2 colour overlaid colour images
Polaroid: filters polarise into orthogonal components
LCD Shutters: 1 eye blocked at a time and synced to the image shown

Question 6

Explain random dot stereograms

Answer 6

Random dot pattern identical in both eyes, section of dots shifted laterally between L/R eye images to create horizontal disparity (encoded in ODCs of V1)

Question 7

Describe 2 oculomotor cues to depth perception

Answer 7

Accommodation: eye accommodates for close vision contracting ciliary muscle allowing pliable crystalline lens to be more rounded

Vergence: vergence angle made between eyes when fixated on object a given distance away

Not accurate if too far away

Question 8

State the 7 main monocular cues to depth perception

Answer 8

1. Linear Perspective: parallel lines converge as distance increases
2. Occlusion: when objects occlude/obscure each other
3. Texture Gradients: texture small dense-packed objects appear further than large less dense-packed
4. Shadows/Shading: biases convex/concave perception
5. Relative Size (Ames Room Illusion - trapezoidal)
6. Aerial Perspective: light scattered/colouration lost at far distances
7. Motion Parallax: relative motion of 2 objects, objects closer appear to be moving faster (not used in paintings)