Space Perception Flashcards
Euclidian Geometry
Parallel lines remain parallel as they extend into space
True or False
The images projected into the retina are non-euclidean
True
How do we perceive space?
- Monocular cues
- Binocular vision and Stereopsis
Name the monocular cues seen in class
- Occlusion
- Metrical depth cue
- Nonmetrical depth cue
- Relative size
- Familiar Size
- Relative height
- Texture Gradient
- Relative metrical depth cue
- Linear Perspective
- Vanishing point
- Areal Perspective
- Motion Parallax
- Optic flow
Occlusion
A cue to relative depth order in which, for example, an object partially obstructs the view of another object.
Metrical Depth Cue
A depth cue that provides quantitative information about distance in the third dimension.
Nonmetrical Depth Cue
A depth cue that provides information about the depth order but not the depth magnitude
Relative Size
A comparison of size between two items without knowing the absolute size of any of them.
All things being equal, we assume that smaller objects are further away from use than larger objects.
Familiar Size
A comparison of size between two items while knowing the absolute size of one of them.
In this case, we can infer the absolute distance since we know the exact size of one of the objects.
Relative Height
For objects touching the ground, those higher in the visual field seem further away.
In the sky above the horizon, objects appearing lower in the visual field seem farther away.
Texture Gradient
A depth cue based on the geometric fact that objects of the same size form smaller, closer spaced images the farther they get.
Texture gradients result from the combination of relative size cues and relative height cues
True or False
Metrical cues give the visual system more information than nonmetrical cues.
True
Relative Metrical Depth Cue
A depth cue that could specify, for example, that object A is twice as far away as object B without providing information about the absolute distance to either A or B.
Linear Perspective
Parallel lines in the threedimensional world will appear to converge in the two-dimensional image as they extend into the distance.
Linear Perspective also results from a combination of the cues of relative size and relative height.
Vanishing Point
The apparent point at which the parallel lines receding in-depth converge.
Areal Perspective
A depth cue based on the implicit understanding that light is scattered by the atmosphere.
Further objects appear fainter, bluer and less distinct.
Motion Parallax
Images closer to the observer move faster than the images farther from the observer.
The brain uses this to calculate the distance between objects in the environment.
Head movements and any other relative movements between observers and objects reveal motion parallax cues.
Optic Flow
The apparent motion of objects in a visual scene produced by the relative motion between the observer and the scene.
Objects in the focus of the expansion will not move.
Objects closer the observer move more rapidly.
Monocular to Binocular Cues
Accommodation
The process by which the eye changes its focus.
Convergence: The ability of the two eyes to turn towards each other. Usually to see objects that are closer.
Divergence: The ability of the two eyes to turn outwards. Usually to see objects that are farther away.
Binocular Vision and Stereopsis
- Binocular Summation
- Binocular Disparity
- Corresponding Retinal Points
- Vieth-Muller Circle (Horopter)
- Diplopia
- Panum’s Fusional Area
- Crossed Disparity
- Uncrossed Disparity
Binocular Summation
The combination of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone.
Binocular Disparity
The differences between the two retinal images of the same scene.
Disparity is the basis of stereopsis, a vivid perception of the threedimensional world that is not available in monocular vision.
Corresponding Retinal Points
A geometrical concept stating that point on the retina of each eye where the monocular retinal images of a single object are formed are at the same distance from the fovea in each eye.
Vieth-Muller Circle
(Horopter)
The location of objects whose image lies on the corresponding points.
The surface of zero disparity.
Diplopia
Double vision.
If visible in both eyes, stimuli falling outside the Panum’s Fusional area will appear diplopic.
Panum’s Fusional Area
The region of space in front and behind the horopter where binocular single vision is possible.
Crossed Disparity
The sign of disparity created by objects in front of the plane of the horopter.
Images in the front of the horopter are displayed to the left of the right eye and to the right of the left eye.
Uncrossed Disparity
The sign of disparity created by objects behind the plane of the horopter.
Images behind the horopter are displaced to the right in the right eye and displaced to the left in the left eye.
True or False
Different binocular neurons in V1 encode all categories of retinal disparity.
True
True or False
The binocular neurons in V1 that encode all categories of retinal disparity aren’t placed in a particular structure
False
They are organized as columns.
Notice:
The binocular neurons in V1 that encode all categories of retinal disparity allow perceiving depth within Panum’s Fusional Area
Stereoscope
A device for presenting an image to an eye and another image to the other eye.
Correspondence Problem
In binocular vision, the problem of figuring out which bit of the image in the left eye should correspond with which bit in the right eye.
Do we have to recognize objects to have stereopsis?
No,
An example is we have 2 teapots, and they are identical but one is located further away. So how does our visual system knows that the far teapots are the same, similarly for the near ones?
Random Dot Stereogram (RDS)
A stereogram made out of a great number or randomly placed dots.
- RDSs contain no monocular cues to depth
- Stimuli visible stereoscopically in RDSs are cyclopean stimuli.
- If the “object” on the right eye is positioned to the left of the object on the left eye (if there is crossing), the object will be perceived in front of the background (and vice-versa)
Cyclopean
Referring to stimuli that are defined by binocular disparity alone.
True or False
Object recognition happens after binocular integration.
True
Binocular Rivalry
The competition of the two eyes for control of visual perception, which is evident when completely different stimuli are presented to both eyes.
