Task 6 - Three Dimensions Flashcards
Cue approach to depth perception
it focuses on identifying information in the retinal image that is correlated with depth in the scen
Occlusion
a signal, or cue, that one object is in front of another – we learn the connection between this cue and depth through our previous experience with the environment
Three major different types of cues
Oculomotor: cues based on our ability to sense the position of our eyes and the tension in our eye muscles
Monocular: cues that work with one eye
Binocular: cues that depend on two eyes
Oculomotor cues are created by
(1) convergence, the inward movement of the eyes that occurs when we look at nearby objects, and
(2) accommodation, the change in the shape of the lens that occurs when we focus on objects at various distances
Monocular cues
Accommodation: described under oculomotor cues
Pictorial cues: which is depth information that can be depicted in a two-dimensional picture
Movement based cues: based on depth information created by movement
Pictorial cues
sources of depth information that can be depicted in a picture
Occlusion
Occlusion occurs when one object hides or partially hides another from view. The partially hidden object is seen as being farther away
Relative height
objects that are below the horizon and have their bases higher in the field of view are usually seen as being more distant
Relative size
when two objects are of equal size, the one that is farther away will take up less of your field of view than the one that is closer – also depends a little on a person’s knowledge of physical sizes
Perspective convergence
the perceptual coming-together of parallel lines (as distance increases)
Familiar size
judge distance based on our prior knowledge of the sizes of objects
Atmospheric perspective
occurs when more distant objects appear less sharp and often have a slight blue tint –The farther away an object is, the more air and particles (dust, water droplets, airborne pollution) we have to look through, making objects that are farther away look less sharp and bluer than close objects
Texture gradient
Elements that are equally spaced in a scene appear to be more closely packed as distance increases
Shadows
Shadows that are associated with objects can provide information regarding the locations of these objects – they also enhance the three-dimensionality of objects
Two different motion-produced cues
(1) motion parallax and
(2) deletion and accretion
Motion parallax
occurs when, as we move, nearby objects appear to glide rapidly past us, but more distant objects appear to move more slowly
Deletion and accretion
Covering is deletion
Uncovering is accretion
Binocular disparity
the difference in the images in the left and right eyes
Corresponding retinal points
the places on each retina that would overlap if one retina could be slid on top of the other
Horopter
which is an imaginary surface that passes through the point of fixation and indicates the location of objects that fall on corresponding points on the two retinas
Angle of disparity
the difference between where the image falls on the eye and the corresponding point
Absolute angle of disparity / absolute disparity
it provides information about the distances of objects — the amount of absolute disparity indicates how far an object is from the horopter — One of the properties of absolute disparity is that it changes every time the observer changes where he or she is looking
Relative disparity
the difference between two objects’ absolute disparities — disparity information that remains the same no matter where an observer looks
Frontal eyes
results in overlapping fields of view
Lateral eyes
result in no overlapping visual fields and therefore cannot use disparity to perceive depth
Binocular depth cells / disparity-selective cells
neurons that are tuned to respond to specific amounts of disparity. The first research on these neurons described neurons in the striate cortex (V1) that responded to absolute disparity
Visual angle
the angle of an object relative to the observer’s eye – when a person moves closer the visual angle becomes larger – The visual angle tells us how large the object will be on the back of the eye
Size consistency
This principle states that our perception of an object’s size remains relatively constant, even when we view an object from different distances, which changes the size of the object’s image on the retina
Size-distance scaling
the mechanism that takes an object’s distance into account
Emmert’s law
The relationship between the apparent distance of an afterimage and its perceived size
Müller-Lyer illusion
the right vertical line appears to be longer than the left vertical line, even though they are both exactly the same length (with the arrows pointing in and out)
Misapplied size constancy scaling
size constancy normally helps us maintain a stable perception of objects by taking distance into account – Gregory suggests that the fins on the right line make this line look like part of an inside corner, and that the fins on the left line make this line look like part of an outside corner
Conflicting cues theory
our perception of line length depends on two cues:
(1) the actual length of the vertical lines, and (2) the overall length of the figure
Ponzo (or railroad track) illusion
both animals are the same size on the page, and so have the same visual angle, but the one on top appears longer
Ames room
causes two people of equal size to appear very different in size
The reason for this erroneous perception of size lies in the construction of the room
Moon illusion
The enlargement of the moon at the horizon compared to the elevated moon – although in both cases they have the same visual angle
Apparent distance theory
the moon on the horizon appears more distant because it is viewed across the filled space of the terrain, which contains depth information; but when the moon is higher in the sky, it appears less distant because it is viewed through empty space, which contains little depth information
Angular size contrast theory
the moon appears smaller when it is surrounded by larger objects – Thus, when the moon is elevated, the large expanse of sky surrounding it makes it appear smaller. However, when the moon is on the horizon, less sky surrounds it, so it appears larger
