comparison org/adelson-notes.org @ 66:eae81fa3a8e0

add camera timing idea.
author Robert McIntyre <rlm@mit.edu>
date Thu, 03 Oct 2013 17:42:48 -0400
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65:1c6af9dd64d5 66:eae81fa3a8e0
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