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

    68 

    69 * Fri Oct  4 2013

    70 

    71   Student report. Talked about how you capture the appearance of a

    72   grape. It's actually quite compicated, involving gloss, spatial

    73   context, etc.

    74 

    75   Turbosquid seems interesting. They sell 3D models of stuff.

    76 

    77   BRDF -- bi-directional reflectance distribution function this shows

    78   how a surface will behave given lighting conditions. Lambertian is a

    79   simple parameterized instantiation of this.

    80 

    81   BSSRDF -- (SS = subsurface) 3D analogue of BRDF

    82 

    83   What would the 3D analiogue of texture be?

    84 

    85   (a : b : c) as (a + b + c : b + c : c) <-- this is just the golden

    86   ratio again!

    87 

    88   CURET BTF Database lol what's this

    89 

    90   This student went and gathered 1000 images of different large

    91   objects made of different materials. The images were gathered off of

    92   Flikr. 

    93 

    94   Then she gave another talk from someone else. It's about assigning

    95   materials to objects and then rendering them. The choice of

    96   materials is determined by some sort of expert system?

    97 

    98   They have made a neat looking interface for human entry of texture

    99   labeling or objects in scenes. The important elements were manual

   100   labels, dynamic display of the current selection, and undo.

   101 

   102   There are papers about mechanical turk engineering.

   103 

   104   lol http://opensurfaces.cs.cornell.edu/

   105 

   106   CUBAM is interesting 2010 "The multidimensional wisdom of crowds."

   107   "Neural Information processing systems" some sort of voting scheme.

   108 

   109   The point of this is apparently to do some kitchen makeover

   110   thing. You would take a picture of your kitchen, or you would look

   111   for a kitchen that looks like yours, and then you would be able to

   112   investigate different textures for your own kitchen.

   113 

   114   apparently "Label ME" has never been appropriately

   115   crowdsourced. Turns out that you get better work if you don't use

   116   idiots to do the work lol.
author	Robert McIntyre <rlm@mit.edu>
date	Thu, 26 Feb 2015 18:03:15 -0800
parents	dfcbbb3d4b9a
children