Perception of Size and Depth in Visual Processing

Pictorial (monocular) cues

Cues that provide depth information using a single eye, including occlusion, relative height, relative size, perspective convergence, familiar size, atmospheric perspective, texture gradient, and shadows.

Motion cues

Cues that provide depth information based on motion, including motion parallax, deletion, and accretion.

Binocular cues

Cues that provide depth information using both eyes, allowing for stereopsis.

Stereopsis

The perception of depth that arises from the brain's processing of the slightly different images received from each eye.

Binocular rivalry

A phenomenon that occurs when each eye is presented with a different image, leading to a competition between the two images for perception.

Monocular rivalry

A phenomenon where two different images are presented to the same eye, leading to a competition for perception.

The Size-Distance equation

A formula that relates the perceived size of an object to its distance from the observer.

Illusions of depth and size

Visual phenomena where the perceived depth or size of an object does not correspond to its actual dimensions.

Occlusion

A pictorial cue where an object that is partially blocked by another object is perceived as being farther away.

Relative height

A pictorial cue where objects positioned higher in the visual field are perceived as being farther away.

Relative size

A pictorial cue where objects that are smaller in size are perceived as being farther away.

Perspective convergence

A pictorial cue where parallel lines appear to converge as they recede into the distance.

Familiar size

A pictorial cue that uses knowledge of the typical size of objects to judge their distance.

Atmospheric perspective

A pictorial cue where distant objects appear hazier and less detailed than closer objects due to the atmosphere.

Texture gradient

A pictorial cue where the density of texture elements increases with distance, indicating depth.

Shadows

A pictorial cue where the presence and direction of shadows provide information about the position and distance of objects.

Motion parallax

A motion cue where objects closer to the observer appear to move faster than objects that are farther away.

Deletion & accretion

Motion cues that involve the gradual occlusion (deletion) and revelation (accretion) of objects as the observer moves.

Accommodation

An oculomotor cue that refers to the adjustment of the eye's lens to focus on objects at different distances.

Convergence

An oculomotor cue that refers to the inward movement of the eyes when focusing on a nearby object.

Rebounding bias

The tendency to perceive motion as rebounding or reversing direction after an initial movement.

Relative size

If two same-size objects appear different size, the one that appears smaller is farther.

Relative height

Below horizon: Objects with higher base are farther. Above horizon: Objects with lower base are farther.

Perspective convergence

Parallel lines of the road appear to converge as they get farther.

Familiar size

Knowing the relative sizes of familiar objects can help resolve which one is closer.

Atmospheric perspective

Far away objects are dimmer and bluer due to particles in the atmosphere.

Texture gradient

Texture patterns shrink as they get farther away.

Motion parallax

A depth cue that involves the apparent motion of objects as the observer moves.

Binocular disparity

Difference between the images on the left and right eyes.

Corresponding points on the retinas

When we converge on an object, the object falls in the same place on the two retinas; namely, on the foveas.

Horopter

The set of points in the visual scene that project to corresponding points on the two retinas (given a certain fixation).

Convergence and divergence

To properly fuse an object that is not in our current horopter, we need to converge or diverge our eyes and accommodate our lenses.

Stereopsis

The impression of a 3-dimensional world provided by binocular cues.

Red/blue (or red/cyan) 3D glasses

One lens is a red-pass filter and the other is a blue-pass filter. Images are created by taking two images with camera lenses ~6cm apart and applying filters.

Size-distance equation

Size ~ Retinal angle x Distance (estimated).

Ponzo illusion

Estimating size requires estimating distance.

Crazy chair illusion

An example of a size-depth illusion.

Ames room

A room designed to create an optical illusion of size.

Sidewalk art

Art created by Julian Beever that creates an illusion of depth.

Simultaneous size contrast

A phenomenon where the perceived size of an object is influenced by the size of surrounding objects.

Dynamic Ebbinghaus

An illusion where the perceived size of a central circle is affected by the size of surrounding circles.

Temporal dynamics of binocular rivalry

Refers to the timing and switching of percepts in binocular rivalry.

Indirect process of size perception

We only really ever know the visual angle of an object; to perceive true size, we estimate distance.

Distance estimation cues

Estimation of distance can be based on occlusion, familiarity, perspective, binocularity, etc.

Visual angle

The angle formed by the lines of sight to the edges of an object.

True size estimation

Combining distance estimates with known visual angle allows us to estimate true size.