Mercurial > thoughts

     1 #+title: Notes for "Special Topics in Computer Vision"

     2 #+author: Robert McIntyre

     3 #+email: rlm@mit.edu

     4 #+description: 

     5 #+keywords: 

     6 #+SETUPFILE: ../../aurellem/org/setup.org

     7 #+INCLUDE: ../../aurellem/org/level-0.org

     8 #+babel: :mkdirp yes :noweb yes :exports both

     9 

    10 * Fri Sep 27 2013

    11 

    12   Lambertian surfaces are a special type of Matt surface. They reflect

    13   light in all directions equally. They have only one parameter, the

    14   amount of energy that is absorbed/re-emitted.

    15 

    16   [[../images/adelson-checkerboard.jpg]]

    17   #+caption: Lol checkerboard illusion.

    18 

    19   Look into Helmholtz' stuff, it might be interesting. It was the

    20   foundation of both vision and audition research. Seems to have took

    21   a sort of Baysean approach to inferring how vision/audition works.

    22   

    23   - Homomorphic filtering :: Oppenhiem, Schafer, Stockham, 1968.  also

    24        look at Stockham, 1972.

    25 

    26   Edwin Land was Adelson's hero back in the day. He needed to create a

    27   color photo for the Polaroid camera. In order to process for

    28   automatic development of film, he had to get a good approximation for

    29   the illumination/reflectance decomposition that humans do, which he

    30   called Retinex.

    31 

    32   Cornsweet square wave grating is cool.

    33 

    34   - Retinex :: use derivatives to find illumination. Sort of

    35                implicitly deals with edges, etc. Can't deal with

    36                non-lambertian objects. 

    37 

    38 

    39   Adelson introduces the problem as an "inverse" problem, where you

    40   try to "undo" the 3-d projection of the world on your retina.

    41 

    42   On the functional view of vision : "What it takes" is to build a

    43   model of the world in your head. The bare minimum to get success in

    44   life is to have a model of the world. Even at the level of a single

    45   cell, I think you still benefit from models.

    46 

    47   Spatial propagation is ABSOLUTELY required to separate embossed

    48   stuff from "painted" stuff. Edges, likewise, MUST have spatial

    49   context to disambiguate. The filters we use to deal with edges must

    50   have larger spatial context to work, and the spatial extent of this

    51   context must be the ENTIRE visual field in some cases!

    52 

    53 ------------------------------------------------------------

    54 

    55 ** Illumination, shape, reflectance all at once

    56    

    57    What if we tried to infer everything together? Some images are so

    58    ambiguous it requires propagation from all three qualities to

    59    resolve the ambiguity.

    60 

    61    Brain has a competing painter, sculptor, and gaffer which each try

    62    to "build" the things in the world. There is a cost to everything

    63    such as paints, lights, and material, and then you try to optmize

    64    some cost function using these primitives.

    65 

    66 

    67    Horn, technical report, 1970
author	Robert McIntyre <rlm@mit.edu>
date	Thu, 03 Oct 2013 17:42:48 -0400
parents
children	036fe1b13120