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PERCEIVING PERCEIVING DEPTH AND SIZE DEPTH AND SIZE ICS 280: Visual Perception ICS 280: Visual Perception DEPTH DEPTH

PERCEIVING DEPTH AND SIZE

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Page 1: PERCEIVING DEPTH AND SIZE

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PERCEIVING PERCEIVING DEPTH AND SIZEDEPTH AND SIZE

ICS 280: Visual PerceptionICS 280: Visual Perception

DEPTHDEPTH

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Slide 3 ICS 280: Visual Perception

Cue ApproachCue Approach

Identifies information on the retinaIdentifies information on the retinaCorrelates it with the depth of the sceneCorrelates it with the depth of the sceneDifferent cuesDifferent cuesPrevious knowledgePrevious knowledge

Slide 4 ICS 280: Visual Perception

Depth CuesDepth Cues

OculomotorOculomotorMonocularMonocularBinocularBinocular

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Slide 5 ICS 280: Visual Perception

OculomotorOculomotor CuesCues

ConvergenceConvergenceInward movement for Inward movement for nearby objectsnearby objectsOutward movements for Outward movements for farther objectsfarther objects

AccommodationAccommodationTightening of muscles Tightening of muscles the change the shape of the change the shape of the lensthe lens

Slide 6 ICS 280: Visual Perception

Monocular Cues (Pictorial)Monocular Cues (Pictorial)

OcclusionOcclusionRelative heightRelative heightCast shadowsCast shadowsRelative sizeRelative sizeFamiliar sizeFamiliar size

Atmospheric perspective Atmospheric perspective Linear perspectiveLinear perspectiveTexture gradientTexture gradientMovementMovement--based cuesbased cues

Motion ParallaxMotion ParallaxDeletion and accretionDeletion and accretion

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Slide 7 ICS 280: Visual Perception

OcclusionOcclusion

Slide 8 ICS 280: Visual Perception

Relative HeightRelative Height

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Slide 9 ICS 280: Visual Perception

Conflicting CuesConflicting Cues

Slide 10 ICS 280: Visual Perception

Cast ShadowsCast Shadows

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Slide 11 ICS 280: Visual Perception

Relative SizeRelative Size

Slide 12 ICS 280: Visual Perception

Familiar SizeFamiliar Size

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Slide 13 ICS 280: Visual Perception

Atmospheric PerspectiveAtmospheric Perspective

Slide 14 ICS 280: Visual Perception

Linear PerspectiveLinear PerspectiveTexture GradientTexture Gradient

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Slide 15 ICS 280: Visual Perception

Presence of GroundPresence of Ground

It helps in perceptionIt helps in perceptionRemoval of ground causes difficulty in Removal of ground causes difficulty in perceptionperception

Slide 16 ICS 280: Visual Perception

Motion ParallaxMotion Parallax

Further points have Further points have lesser parallaxlesser parallaxCloser points move Closer points move lessless

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Slide 17 ICS 280: Visual Perception

Deletion and AccretionDeletion and Accretion

Slide 18 ICS 280: Visual Perception

Binocular CuesBinocular Cues

Binocular disparity and Binocular disparity and stereopsisstereopsisCorresponding pointsCorresponding points

Correspondence problemsCorrespondence problemsDisparity information in the brainDisparity information in the brain

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Slide 19 ICS 280: Visual Perception

Binocular Disparity and Binocular Disparity and StereopsisStereopsis

Binocular disparityBinocular disparityDifference in the images of the two eyesDifference in the images of the two eyes

StereopsisStereopsisDisparity is transformed into perception of depthDisparity is transformed into perception of depth

Discovery of stereoscope in 1800sDiscovery of stereoscope in 1800s

Slide 20 ICS 280: Visual Perception

Corresponding Retinal PointsCorresponding Retinal Points

Corresponding Points

Points on horopter are images at corresponding points of the two eyes

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Slide 21 ICS 280: Visual Perception

Corresponding Retinal PointsCorresponding Retinal Points

Disparity is defined by the angle between the

image of a point and the corresponding point of its image on the other eye subtended from focus

Slide 22 ICS 280: Visual Perception

Crossed and Uncrossed Crossed and Uncrossed DisparityDisparity

For points in front of For points in front of the the horopterhoropter

The image is on the The image is on the inner side of the retina inner side of the retina from the image of a from the image of a point on point on horopterhoropter

For points behind the For points behind the horopterhoropter

The image is on the The image is on the outer side of the retina outer side of the retina from the image of a from the image of a point on point on horopterhoropter

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Slide 23 ICS 280: Visual Perception

Disparity in BrainDisparity in Brain

Striate cortex has binocular depth cells or Striate cortex has binocular depth cells or disparity detectorsdisparity detectorsDisparity selective cellsDisparity selective cellsAlso selective about crossed or uncrossed Also selective about crossed or uncrossed disparitydisparityHowever, important is to solve the However, important is to solve the correspondence problemcorrespondence problem

Matching images of the same point on two different Matching images of the same point on two different eyeseyesOnly after this we can find the disparityOnly after this we can find the disparity

Slide 24 ICS 280: Visual Perception

How do they work together?How do they work together?

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Slide 25 ICS 280: Visual Perception

Depth perception in other speciesDepth perception in other species

Frontal Eyes needed for binocular disparityFrontal Eyes needed for binocular disparityRabbits etc cannot use disparity for depth Rabbits etc cannot use disparity for depth Pigeon has 35 degree overlapPigeon has 35 degree overlap

Other Other informationsinformationsNotonectaNotonecta : Movement in retina: Movement in retinaLocust : Movement parallaxLocust : Movement parallaxBat : Sonar cuesBat : Sonar cues

SIZESIZE

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Slide 27 ICS 280: Visual Perception

Depends on depth estimationDepends on depth estimation• All depth cues present• Closing one eye• No binocular cues

• Through a peephole• No monocular cues

•Adding drapes• No shading cues

Slide 28 ICS 280: Visual Perception

Size ConstancySize Constancy

SizeSize--distance Scalingdistance ScalingS = S = K(RxDK(RxD))K = 1/FK = 1/F

Focus of the eye

R = size of the retinal

image

D = depth of the object

S = perceived size of the object

F = focal length of eye

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Slide 29 ICS 280: Visual Perception

Relative sizeRelative size

Visual IllusionsVisual Illusions

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Slide 31 ICS 280: Visual Perception

MullerMuller--LyerLyer IllusionIllusion

Slide 32 ICS 280: Visual Perception

Explanation 1: Misapplied size Explanation 1: Misapplied size constancy scalingconstancy scaling

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Slide 33 ICS 280: Visual Perception

Explanation 2 : Conflicting Cues Explanation 2 : Conflicting Cues TheoryTheory

Slide 34 ICS 280: Visual Perception

PonzoPonzo IllusionIllusion

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Slide 35 ICS 280: Visual Perception

Ames RoomAmes Room

Slide 36 ICS 280: Visual Perception

Moon IllusionMoon Illusion

Apparent distance theoryApparent distance theoryAngular sizeAngular size--contrast theorycontrast theory