Perception 3 - depth & visual scene analysis Flashcards
Difficulties making perceiving machinery
Computer struggle with image complexity and organising scenes into distinct objects
How do we perceive depth?
Monocular and binocular cues
Perceiving depth- monocular cues
Work with one eye
eg. relative height, relative size, occlusion, linear perspective, swhadows, shading
Monocular cues- relative height and size
Top down- uses prior knowledge about relative sizes of objects when judging distance
Monocular cues- occlusion
Closer objects block out further away ones
Monocular cues- linear perspectiva and texture gradient
eg. parallel lines extending away
texture elements- get smaller and more dense with distance
Foreshortening- occurs when a surface is tilted away eg, circles become ovals
Monocular cues- motion parallax
When moving, more distant objects glide past us slower than nearer objects
Monocular cues- shadows and shading
Creates depth perception
Binocular disparity- stereoscopic vision
Our two eyes receive slightly different images of the world
Binocular disparity- disparity
This creates a difference in image location of an object seen by left and right eyes
Size of disparity depends on depth
Binocular disparity- horopter
Set of points in space that project to corresponding positions in the two retinas
Objects closer than horopter have crossed disparities
Objects further than horopter have uncrossed disparities
Perceiving objects- illusory contours
Some images evoke perception of edges
Gestalt principles of perceptual organisation
Elements in an image are grouped to create larger objects
Gestalt principles- proximity
Objects that are close together are grouped together
Gestalt principles- similarity
Things that are similar are grouped together
Similarity may override proximity
