Visual Perception:Visual Perception:It Is All In Your It Is All In Your

MindMind

Mona Moshtaghi

Neuroscience

Texture

Shape

Size

Disparity

Motion

Processing

Constraint

http://homepage.psy.utexas.edu/homepage/class/Psy308/Salinas/Vision/Vision.html

Beginnings of Human Perception

• Perception of a real object is based on “sensory data representing the physical properties of the object such as its weight, reflectance, rigidity, stiffness and texture.”

• Plato– “Platonic Solids”

• Aristotle– “There is nothing in the mind that

was not first in the senses.”

• David Marr– Vision

http://ucelinks.cdlib.org:8888/sfx_local?sid=Entrez:PubMed&id=pmid:19800910

James J. Gibson

• Psychologist in the field of visual perception

• Introduced texture gradient

____________________________________________

• Visual texture cue to the 3D structure of surfaces

• Texture studied as 3D cue (computational and computer vision)

http://www.journalofvision.org/content/6/9/3.long

http://www.journalofvision.org/content/6/9/3.long

Decompositions of Texture Gradients Into Different Components

David Marr

Three Levels of Understanding Complex Information-Processing Devices

Computational Approach Most abstract level

Describes the problem the system is trying to solve & the constraints it uses in order to solve it

Representation and Algorithmic

Addresses the questions of representations

Hardware Implementation

Involves the details of the hardware in which the algorithm is embodied

http://www.cs.huji.ac.il/~yweiss/intro/node2.html

Marr’s “2.5D Sketch”• Opaque cube• 7 of the 8 vertices• 9 of the 12 edges• More than half of the 3D shape can be seen

when represented by contours or vertices

http://ucelinks.cdlib.org:8888/sfx_local?sid=Entrez:PubMed&id=pmid:19800910

Computational Geometry

• Vertices:

0-dimensional cells

• Edges:

1-dimensional cells

• Regions or Faces:

2-dimensional cells

http://graphics.stanford.edu/courses/cs268-09-winter/http://illusion.scene360.com/3d/5105/computational-geometry/

A, B: In the Ponzo illusion, the two converging lines provided the depth impression that the two physically identical objects were located at different distances from the observer, and the distant object looks larger than the object that appears closer in space.

C: In the Ebbinghaus illusion, the object surrounded by small items looks larger than a physically identical object surrounded by big items.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3062603/figure/F1/

Art &

Perspective

Cayetano Ferrer

http://illusion.scene360.com/art/13257/invisible-mail-packages-street-sign-and-billboard/

Mary Temple

Latex paint on walls

Illusion of light coming from a window into a room

Research continues…

How does the brain accomplish diverse functions of scene

understanding?

http://homepage.psy.utexas.edu/homepage/class/Psy308/Salinas/Vision/Vision.html

WhereWhere

WhatWhat

Disentangling scene content from spatial boundary: complementary roles for the parahippocampal place area and

lateral occipital complex in representing real-world scenes.

•Analysis of the visual scene account for the objects and the spatial layout of surfaces in a scene

• Parahippocampal place area (PPA)

same spatial boundaries

• Lateral occipital complex (LOC)

same content

http://www.ncbi.nlm.nih.gov/pubmed/21273418

New approach to the perception of 3D shape based on veridicality, complexity, symmetry

and volume.

• 3D shape is unique in perception– Complexity identification of objects

• 3D shape perception is veridical (car, chair, etc)

http://www.ncbi.nlm.nih.gov/pubmed/19800910

Thank You

Hide & Seek That Beer…