Depth, Size And Illusions Flashcards
We perceive…
A 3D world but the image on our retina is 2D
Cues
Use cues to extract depth info
Cues are info in the retinal image that’s correlated with depth
Across our lives we learn to associate cues with depth
Associations become automatic through repeated exposure
What happens to the image on the retina
The image on the retina is upside down. Perception flips it
3 broad cues
Bits of info that are:
1: oculomotor = minds get from muscles around eye (sensing position of eyes)
2: monocluar= extracted from images by either eye independently
3: binocular = extracted from images by both eyes working together
Ocular convergence
Oculomotor Cue
Inward movement of eyes and the corresponding muscle tension when focusing on near objects
Lens accomodation
Oculomotor cue where tension is detected in the ciliary muscles
Accomodation is the change in lens shape when focusing on near or far objects
Far = relaxes
Close = contacts
Monocular cues are mostly
Pictorial cues - information extracted from 2D images
Also non-pictorial cues - info cannot be extracted from static 2D image
Occlusion
When an object partially covers another
Object that is occluded is usually deeper in the visual field
Relative height
Looking below horizon = objects higher are more distant
Looking above horizon = objects lower are more distant
Relative size
When objects are equal size, the closer ones will take up more of your visual field
Perspective convergence
Parallel lines appear to approach each other at greater distances
Perspective convergence in art
European art- effect loss in middle ages and reemerged in Renaissance
Familiar size
Knowledge of familiar objects can help us infer which objects are closer
Atmospheric perspective
Distant objects are blurrier and can have blue/grey tint
Texture gradient
Equally spaced elements are more closely packed as distance increases
Shadow
Position of objects shadow can be helpful to perceive depth
Cues combined
Cues are more useful when they give consistent info
Motion parallax
Non-pictorial monocular cue
Near objects glide rapidly past and far objects move slowly
Occlusion via movement
Non-pictorial cue
Objects are covered and uncovered as we move relative to them
Covering = deletion
Uncovering = accretion
Binocular cues involve
Comparing the slightly different views presented in each eye
Binocular disparity
Disparity between different images created by objects falling in different locations on the retina
Corresponding points
The forea is always the corresponding point as whatever is focused on falls on the same spot on both retinas
Horopter
Unfocused things fall on the corresponding point if they are on the an arc called the horopter
Images not on the horopter fall on non-corresponding points
Crossed disparity
Crossed: object inside horopter = appears closer
Uncrossed: object outside horopter= appears further