cavanagh's pseudorealism

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cavanagh's pseudorealism
Jan 23 - David Thompson
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(Outline)

1. Marr's Model 2. 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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the Marr vision model
Object
object-centric coordinates
3D model
2½D sketch
viewer-centric coordinates
primal sketch
stimulus
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the Marr vision model
recognition with object-centric 3D models
Object
object-centric coordinates
3D model
2½D sketch
viewer-centric coordinates
primal sketch
bottom-up reconstruction of shape from image
features
stimulus
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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!)
attached shadow contour
cast shadow contour
inferred external contours
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Cavanagh's claim

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
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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
memory
basic recognition with 2D primitives
3D shape
2D shape
top-down feedback
stimulus
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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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take-home lessons?
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
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Two models of Human visual processing
Marr's model (circa 1980) Cavanagh's
model (circa 1990)
object recognition by matching 3D models
Object
basic recognition with 2D primitives
memory
3D model
3D shape
2½D sketch
2D shape
feedback
primal sketch
reconstruction of shape from image features
stimulus
stimulus