Download
1 / 62
620 likes | 829 Vues
Perceptual Organization & Scene A nalysis. NRS 495 – Neuroscience Seminar Christopher DiMattina , PhD. How do we parse the visual scene?. Novel combinations of objects. Perceptual organization and Gestalt grouping. The problem of grouping.
E N D
Perceptual Organization & Scene Analysis NRS 495 – Neuroscience Seminar Christopher DiMattina, PhD
How do we parse the visual scene? NRS 495 - Grinnell College - Fall 2012
Novel combinations of objects NRS 495 - Grinnell College - Fall 2012
Perceptual organization and Gestalt grouping NRS 495 - Grinnell College - Fall 2012
The problem of grouping • The visual system goes from pixel intensities to objects and appropriate groupings of objects NRS 495 - Grinnell College - Fall 2012
Schools of early psychology • Structuralists believed that perceptions were built up of atoms of sensation • Gestalt school argued that the perceptual whole is greater than the sum of its parts (gestalt = ‘form’) • Gestalt psychologists proposed rules for how the visual system groups features into perceptual wholes PSY 295 - Grinnell College - Fall 2012
Good continuation • Similarly oriented lines are seen as part of the same contour • Reflects the structure of the natural sensory environment PSY 295 - Grinnell College - Fall 2012
Similarity • Different image regions have different statistical properties • Group together regions with similar properties PSY 295 - Grinnell College - Fall 2012
Proximity • Nearby object tend to be grouped together • Note horizontal rather than vertical grouping PSY 295 - Grinnell College - Fall 2012
Gestalt grouping principles NRS 495 - Grinnell College - Fall 2012
Degrees of grouping NRS 495 - Grinnell College - Fall 2012
Tradeoff between color and proximity NRS 495 - Grinnell College - Fall 2012
Synchrony NRS 495 - Grinnell College - Fall 2012
Common region NRS 495 - Grinnell College - Fall 2012
Connectedness NRS 495 - Grinnell College - Fall 2012
Over-ruling proximity PSY 295 - Grinnell College - Fall 2012
Quantitative measurements of grouping NRS 495 - Grinnell College - Fall 2012
Repetition discrimination task • Are repeated items squares or circles? NRS 495 - Grinnell College - Fall 2012
Effects of size in common region NRS 495 - Grinnell College - Fall 2012
Organization in three dimensions NRS 495 - Grinnell College - Fall 2012
Grouping and lightness constancy NRS 495 - Grinnell College - Fall 2012
Grouping and visual completion NRS 495 - Grinnell College - Fall 2012
Uniform connectedness NRS 495 - Grinnell College - Fall 2012
Effects of experience NRS 495 - Grinnell College - Fall 2012
Effects of experience NRS 495 - Grinnell College - Fall 2012
Camouflage • The goal of camouflage is to prevent accurate feature grouping so that you cannot perceive animal PSY 295 - Grinnell College - Fall 2012
Web Activity • http://sites.sinauer.com/wolfe3e/chap4/gestaltF.htm NRS 495 - Grinnell College - Fall 2012
Region and texture segmentation NRS 495 - Grinnell College - Fall 2012
Need to partition into regions NRS 495 - Grinnell College - Fall 2012
Finding edges • One way to detect objects is to find their edges • However, not all edges correspond to object boundaries • Output of computer vision edge-detector PSY 295 - Grinnell College - Fall 2012
Edge detection does not always find region boundaries NRS 495 - Grinnell College - Fall 2012
Region-based approaches • Work in machine vision groups pixels by similarity in gestalt cues like luminance, color, texture, etc… • Segments image using graph-theoretic methods • Works better than edge detection methods NRS 495 - Grinnell College - Fall 2012
Parsing • Sharp concave discontinuities provide an important cue for parsing objects into parts NRS 495 - Grinnell College - Fall 2012
Texture segregation NRS 495 - Grinnell College - Fall 2012
Texture segregation NRS 495 - Grinnell College - Fall 2012
Physically different textures don’t separate NRS 495 - Grinnell College - Fall 2012
Identical second and third order statistics but they separate NRS 495 - Grinnell College - Fall 2012
Malik and Perona model NRS 495 - Grinnell College - Fall 2012
Filters in the Model NRS 495 - Grinnell College - Fall 2012
Filter outputs NRS 495 - Grinnell College - Fall 2012
Texture boundaries NRS 495 - Grinnell College - Fall 2012
Model and experiment NRS 495 - Grinnell College - Fall 2012
Figure and ground organization NRS 495 - Grinnell College - Fall 2012
Ambiguous figure/ground organization NRS 495 - Grinnell College - Fall 2012
Faces or vase? NRS 495 - Grinnell College - Fall 2012
Border ownership cells in V2 PSY 295 - Grinnell College - Fall 2012
Meaningfullness NRS 495 - Grinnell College - Fall 2012
Visual completion NRS 495 - Grinnell College - Fall 2012
Both familiar and unfamiliar completion NRS 495 - Grinnell College - Fall 2012
Relatability • Kellman and Shipley outlines rules for when two occluded segments are joined NRS 495 - Grinnell College - Fall 2012
