Advances in Visual Perception PSYC 526 Fall Profs

Advances in Visual Perception PSYC 526 Fall Profs. Fred Kingdom & Kathy Mullen

Lecture 8 “Seeing Depth” Reading Goldstein 5 th ed. , Chs. 8 & 9; 6 th ed. Ch. 7 & 9 (p 302307); 7 th ed. Ch. 8. Frisby, "Seeing with two eyes" Ch 7 in Seeing. Oxford University Press (1979).

Seeing Depth Part I Cues to depth Part II Stereopsis

Part I. Cues to depth

Position in field of view Occlusion/Interposition Object size Cues to depth Texture gradients Linear perspective Shading

Texture gradients/Perspective

Occlusion/Interposition Atmospheric: Blueing with distance

Depth from shading

Kurt Wenner

Part II. Stereopsis - Definition - Evidence for modularity - Retinal disparity - Horopters - Stereoacuity - Stereoscopes and anaglyphs - Form-from-stereopsis - Correspondence problem - Autostereograms

definition………. . Stereopsis is the means by which we determine the relative depth of objects by virtue of the fact that our two eyes view the world from a slightly different angle.

Evidence for modularity 1. Phenomenonological irreducibility 2. Stereoblindness 3. Disparity-sensitive neurones 4. Depth after-effect

Retinal disparity

more definitions……. Retinal disparity is the difference in angle subtended by the image of an object in the two eyes, relative to fixation. Stereoacuity is the minimal detectable stereoscopic depth in units of disparity. Normal = 5 -15 secs of arc; best is 2 secs.

Horopters

Wheatstone stereoscope

Principle of anaglyphs

Effect of disparity

Random-dot stereogram Figural stereogram

Random-dot stereogram Figural stereogram

Form from stereopsis Figural stereogram Random-dot-stereogram

‘False-target’ or stereo-correspondence problem

Autostereogram

Autostereogram

Marr & Poggio’s cooperative network model for solving the stereo-correspondence problem

Input stereogram Marr & Poggio’s ‘coarse-to-fine’ filtering model for solving the stereocorrespondence problem Coarsefiltered Mediumfiltered Finefiltered Zero-crossing maps