cavanagh's pseudorealism jan 23 - david thompson
TRANSCRIPT
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cavanagh's pseudorealism
Jan 23 - David Thompson
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(Outline)
1. Marr's Model2. Cavanagh's Model 3. What more can artists tell us about vision?
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the Marr vision model
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the Marr vision model
input image
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the Marr vision model
primal sketch
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the Marr vision model
2.5-D sketch
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the Marr vision model
3D model
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stimulus
2½D sketch
Object
3D model
primal sketch
viewer-centric coordinates
object-centric coordinates
the Marr vision model
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stimulus
2½D sketch
Object
3D model
bottom-up reconstruction of shape from image features
recognition with object-centric 3D models
primal sketch
viewer-centric coordinates
object-centric coordinates
the Marr vision model
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Geons(Biederman '87)
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Cavanagh's model
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two-tone images
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hair (not shadow!)
inferred external contours
“attached shadow” contour
“cast shadow” contour
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A. Finding 3D structure in two-tone images requires distinguishing cast shadows, attached shadows, and areas of low reflectivity
B. The images do not contain this information a priori
D. Therefore, our recognition process must involve matching viewpoint-specific 2D templates
Cavanagh's claim
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What else can art tell us about object recognition?
Cavanagh's model
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What else can art tell us about object recognition?
Cavanagh's model
neurobiological evidence!(Logothetis '95)
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What else can art tell us about object recognition?
Cavanagh's model
stimulus
2D shape
memory
3D shape
top-down feedback
basic recognition with 2D primitives
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shadows and lighting
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transparency
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humans don't do ray tracing
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line drawings are universal
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recognition with few cues
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Human object recognition uses shortcuts, not complete physical models - local lighting - simplified reflections
At least some of our processing happens through “simple vision” - viewer-centric 2D template matching - simple 3D memory provides top-down feedback
take-home lessons?
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Marr's model (circa 1980) Cavanagh's model (circa 1990)
Two models of Human visual processing
stimulus
stimulus
2D shape
memory
3D shape
2½D sketch
Object
3D model
feedback
basic recognition with 2D primitives
reconstruction of shape from image features
object recognition by matching 3D models
primal sketch