PSY 162 Lecture Notes - Lecture 18: Outlandish, Depth Perception
Local Vs. Global…
● Local - within one region of painting
● Global - across the entire image
● Images need to be locally consistent
● But not globally-
How Do We Organize an Entire Scene?
● Virtually every sensory experience we have is computed by local opponent mechanisms
○ Computations about depth are computed early in a small receptive fields
○ You have to know what is going on in a small section of the painting to
understand what is going on throughout the painting
M.C. Escher
● Bridged a period of
● Between surrealism & optical art movements
Shadows?
● In Eastern art- shadows in art are relatively recent
● In the west-
○ DaVinci
○ First to make a systematic study of shadow
○ For centuries, artists ignored the laws of physics
But…
● Our visual systems don’t mind too much
● Computations about depth from shading & illumination of objects begin with local
computations
● Images do not have to be globally consistent to generate a sensation of depth & shadow
● We don’t need to understand Newton!
Shadows
● Our visual system assumes the laws of physics are being obeyed
○ Because they probably are…
○ And if not, there’s not much use knowing about it
○ Artists ignored the laws of physics
○ Sometimes with weird consequences to depth perception
Also… Mirrors
● Because light travels in a straight line-
● Almost any depiction you see of a mirror is physically impossible
The Spatial Organization of the Scene
● Although you notice the occlusion cues are inconsistent
● It takes you a moment longer than it “should”
● This is because the spatial organization is local first-
● You process the bits before the whole
When Local & Global Conflict
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Local - within one region of painting. Virtually every sensory experience we have is computed by local opponent mechanisms. Computations about depth are computed early in a small receptive fields. You have to know what is going on in a small section of the painting to understand what is going on throughout the painting. In eastern art- shadows in art are relatively recent. First to make a systematic study of shadow. For centuries, artists ignored the laws of physics. Our visual systems don"t mind too much. Computations about depth from shading & illumination of objects begin with local computations. Images do not have to be globally consistent to generate a sensation of depth & shadow. Our visual system assumes the laws of physics are being obeyed. And if not, there"s not much use knowing about it. Sometimes with weird consequences to depth perception. Because light travels in a straight line-
