cavanagh's pseudorealism jan 23 - david thompson
TRANSCRIPT
cavanagh's pseudorealism
Jan 23 - David Thompson
(Outline)
1. Marr's Model2. Cavanagh's Model 3. What more can artists tell us about vision?
the Marr vision model
the Marr vision model
input image
the Marr vision model
primal sketch
the Marr vision model
2.5-D sketch
the Marr vision model
3D model
stimulus
2½D sketch
Object
3D model
primal sketch
viewer-centric coordinates
object-centric coordinates
the Marr vision model
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
Geons(Biederman '87)
Cavanagh's model
two-tone images
hair (not shadow!)
inferred external contours
“attached shadow” contour
“cast shadow” contour
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
What else can art tell us about object recognition?
Cavanagh's model
What else can art tell us about object recognition?
Cavanagh's model
neurobiological evidence!(Logothetis '95)
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
shadows and lighting
transparency
humans don't do ray tracing
line drawings are universal
recognition with few cues
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?
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