Four levels of protein structure Linear Sub-Structure 3D Structure Complex Structure.
Perception I: 3D Structure from 2D Projectionsweb.mit.edu/~9.00/www/handouts/5perception1.pdf ·...
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9.00 Introduction to Psychology Week 5, Lecture 1 Perception 1: 3D Structure from 2DProjections 1 Perception I: 3D Structure from 2D Projections The Importance of Illusions • Naïve realism: refuted by illusions • Illusions raise doubt about knowledge – Philosophical skepticism • Relativism and social constructionism: the opposite of naïve realism • Intermediate position: Perception as an adaptative (but fallible) mechanism • Illusions unmask the workings of perceptual mechanisms The Inherent Ambiguity of Perception
Transcript of Perception I: 3D Structure from 2D Projectionsweb.mit.edu/~9.00/www/handouts/5perception1.pdf ·...
9.00 Introduction to PsychologyWeek 5, Lecture 1
Perception 1: 3D Structure from 2DProjections
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Perception I: 3D Structure from 2D Projections
The Importance of Illusions
• Naïve realism: refuted by illusions• Illusions raise doubt about knowledge
– Philosophical skepticism• Relativism and social constructionism: the
opposite of naïve realism• Intermediate position: Perception as an
adaptative (but fallible) mechanism• Illusions unmask the workings of perceptual
mechanisms
The Inherent Ambiguity of Perception
9.00 Introduction to PsychologyWeek 5, Lecture 1
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9.00 Introduction to PsychologyWeek 5, Lecture 1
Perception 1: 3D Structure from 2DProjections
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Size Constancy Shape Constancy
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The Ponzo Illusion
Size constancy as an
explanation for the Ponzo illusion
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The Ames Room Some cues to depth:
1. Shading
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Some cues to depth:
1. Shading 2. Texture gradient
Some cues to depth:
1. Shading 2. Texture gradient
3. Linearperspective
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Some cues to depth:
1. Shading 2. Texture gradient
3. Linearperspective
4. interposition
The Moon Illusion
• Size constancy and lack of depth cues as an explanation
Motion Parallax
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Binocular (2-eyed) Vision Binocular Depth Cues
• Binocular Convergence (rangefinder)• Binocular Parallax or Disparity (stereo)
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How to Make a Stereoscopic Illusion• Draw or photograph a scene twice, once
from the left eye’s vantage point, once from the right’s
• Present one picture to each eye:
• Presto! The person sees in depth.• Stereo illusions as proof of stereo vision
Why it’s Not so Easy to Design a Stereoscope:
• The accommodation (focusing) reflex:
• The convergence (rangefinder) reflex: Problem: The accommodation and convergence reflexes are coupled!
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Ways of Decoupling Accommodation and Convergence
• Free fusion• Wheatstone Stereoscope
Ways of Decoupling Accommodation and Convergence
• Free fusion• Wheatstone Stereoscope• Brewster’s stereoscope:
Ways of Decoupling Accommodation and Convergence
• Free fusion• Wheatstone Stereoscope• Brewster’s stereoscope• A modern version of Brewster’s stereoscope:
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Ways of Decoupling Accommodation and Convergence
• Free fusion• Wheatstone Stereoscope• Brewster’s stereoscope (= “Viewmaster”)• The color anaglyph:
– Red lens: white looks red (neutral), red looks red (neutral), green looks black
– Green lens: white looks green (neutral), red looks black, green looks green (neutral)
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Ways of Decoupling Accommodation and Convergence
• Free fusion• Wheatstone Stereoscope• Brewster’s stereoscope (= “Viewmaster”)• The color anaglyph• The polarizer anaglyph:
– Filter on projector, filter over eye oriented same way: transparent
– Filter on projector, filter over eye oriented at right angles: opaque
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Ways of Decoupling Accommodation and Convergence
• Free fusion• Wheatstone Stereoscope• Brewster’s stereoscope (= “Viewmaster”)• The color anaglyph• The polarizer anaglyph• Virtual reality
The Autostereogram
• Wallpaper autostereograms• Random pattern autostereograms
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A random-dot color anaglyph Random-Dot Stereograms
(not autostereograms – still need a viewer or other trick)
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What Random-Dot StereogramsShow:
• The brain does not need to recognize a whole object in each eye to solve the correspondence problem
• Somehow, the brain solves thecorresondence problem just using bits of texture
• Then it sees the object – with the “Cyclopean” eye
The Random-DotAutostereogram
• Wallpaper stereogram + Random-DotStereogram
The Random-Dot Autostereogram
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Why Cyclopean Vision?
