lecture 6- depth perception

distance to judge ambient distance accurately + study

• 20 feet

• Loomis et al: p’s looked at a scene, closed their eyes & walked to a predesignated object

4 types of cue to depth

• oculomotor

• pictorial/monocular

• motion-produced

• binocular disparity

what is the strongest cue for depth

binocular disparity

what are oculomotor cues + what do you experience

cues that depend on our ability to sense the position of our eyes & tension in our eyes

• convergence

• accomodation

what is convergence

when eye muscles cause eye to look inward

relationship between object distance & convergence

closer object = greater convergence

• closer object = ciliary muscles contract, fibers slack, lens rounds

what are pictorial/monocular cues

• cues that can be depicted in a still picture

• would work if you had 1 eye shut

8 types of pictorial cues

1. overlap/occulsion

2. relative size

3. relative height

4. atmospheric perspective

5. familiar size

6. linear perspective

7. shading & shadow

8. texture gradient

how is relative size a pictorial cue

retinal size of objects get smaller as they get further away

what is size constancy

an object can look the same size at different distances

• normally increased distance = decreased retinal image size

what is the opposite of size constancy

emmert’s law

what is emmert’s law

objects that produce the same size retinal image will look as though they’re different sizes depending on the distance

• perceived object size increases as perceived distance from observer increases

how is relative height a pictorial cue (3 things)

• objects that get further away get closer to the horizon

• if multiple objects are below eye height the highest object is furthest away

• if objects are above eye height then the lowest object is furthest away

how is atmospheric perspective a pictorial cue

distant objects appear less sharp because theres more air + particles to look through

how is linear perspective a pictorial cue + how does this relate to retina

• parallel lines converge as they get further away

• lines don’t appear straight in the retina because retina is curved

2 types of shadow

• attached

• detached

which type of shadow is a stronger pictorial cue

detached

what is an attached shadow + how is it a pictorial cue

• shading that results from depth within an object

• tells us the direction of a light source

what is an deathbed shadow + how is it a pictorial cue

• shadow that an object casts on another object (eg. shadow from object onto the ground)

• gives an indication of where objects are in space

how is a texture gradient a pictorial cue

texture becomes smaller/finer as distance from observer increases

what are motion-produced cues

cues that depend on movement of the observer or movement of objects in the environment

2 types of motion-produced cues

• motion parallax

• deletion & accretion

what is motion parallax + who is it used by

• when an observer moved relative to a 3D scene close objects appear to move rapidly & far objects appear to move more slowly

• used by animals that don’t have much binocular overlap (birds & squirrels)

  • also a type of monocular cue

what is deletion & accretion

• deletion: when an object moves in front of another (front object covers more of the back object)

• accretion: when an object moves away from another (front object covers less of the back object)

what is binocular disparity

cues that depend on the fact that slightly different images of a scene are formed on each eye

• basis of stereoscope

what are corresponding retina points

• for every point on 1 retina theres a corresponding point on the other

• points would be identical if 1 retina was superimposed on the other

• when you foviate on an object it stimulates corresponding points in both eyes

what do non-corresponding retinal points create

disparity

link between disparity and depth perception

• amount of disparity tells us how far non-focused objects are from focused objects

• theres no disparity at the point of fixation (what you’re focusing on)

• other objects fall on non-corresponding points

relationship between binocular disparity and distance

diminishes with distance, determined by distance of the eyes

what is hyperstereo

image which uses a larger distance between left & right lenses which can give increased depth from disparity

what is a stereogram

3D image produced by presenting the same image to both eyes but one image is shifted slightly left/right

• shifted area appears as displaced in depth

9 types of stereogram

1. random dot

2. animated autostereogram

3. colour filters (red/blue 3D glasses)

4. orthotereography (2 pictures at the same time in slightly different positions)

5. shutter glasses

6. lenticular displays (eg: picture changing rulers)

7. parallax barrier technology

8. VR

9. wiggle stereoscope