Computing & the Arts

(outline)

Professor Frederic F. Leymarie
2004-2007



Lincoln in Dalivision (1974-76), Salvador Dali (1904-1989)
Salvador Dali's wife Gala is contemplating the Mediterranean;
seen from far away the canevas is the portrait of Abraham Lincoln.


1. Computational theories of Visual Perception



"Classical" theories of visual perception in computing:
It is assumed that an understanding of the world that surrounds us can be abstracted from sensing data, and in particular from retinal images.

Motivation comes from the known physiology of the visual system of primates, from the retina and its optics (the "camera"), through visual pathways (early "filtering" and communication), to the first layers in the visual cortex (early "feature" reconstruction).





A cross section of the retina (of a rabbit), after Kessel & Kardon, 1979.
Light arrives from the bottom, traverses the entire retina, to reach the
photoreceptors (cones and rods) at the top. A photochemical reaction
creates electrical potential variations in the membrane which percolate
back to the ganglion cells (at the bottom) giving rise to all-or-none action potentials.
More than 1 million ganglion cell axons make up the optic nerve, along which
the spikes travel toward the LGN and visual cortex for processing.
Adapted from Figure 3.1, "The Early Visual System," Christof Koch, 2003.

 Left: schematic drawing by Santiago Ramon y Cajal (circa 1900).
Right: section through a rat retina.
Adapted from Fig.2 @ http://www.fz-juelich.de/ibi/ibi-1/Retina/











ABSTRACTION of the complexity of the world is the GOAL here ("reductivism").

It is also a systemic paradigm: what is the process and its structure (dynamics) which permits to process visual data (photons collected onto the retina) and produce object and scene understanding.

The Sensori-neural Basis of the Color Experience.

David Marr's model

A "bottom-up" approach, which seeks to build abstractions of objects, scenery, the world.

Major challenges to this "classical" approach:


There is no room for a high resolution fully spatial rendition of the actual object being viewed.

From "The Epistemology of Conscious Experience," by Steven Lehar.






Visual "illusions" are not understood by this paradigm

"How to outsmart the system:"  http://www.cs.unm.edu/~leigh/pix/

Gestalt Principles


Our brain perceives wholes out of incomplete elements placed in contexts.




Shape and parts


"Human vision organizes object shapes in terms of parts and their spatial relationships."




Visual Illusions (more on..)





References/Links

[BI150]
Course in Neurobiology, CalTech:
http://www.cns.caltech.edu/bi150/
Lecture notes on the Visual system:
1. Retina and LGN
2. Primary visual cortex and color processing
3. Higher visual processing

[Eye:Physio:2004+]
Physiology of the eye
http://www.siumed.edu/~dking2/ssb/eye.htm

[Koch:EarlyVisualSysCh3:2003]
Koch, C., "Early Visual System," Ch. 3 ("The First Steps in Seeing"), pp. 51-67, Aug. 2003.
Local copy

[UniOfCalgary]
The Bases of Colour Vision, Vision and Aging Lab, Psychology, University of Calgary.


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Last update: Oct. 9, 2007