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