HW2 FAQ

From CS223B Wiki

Revision as of 08:31, 26 January 2009 by Jinhae (Talk | contribs)
(diff) ← Older revision | Current revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Contents

CS223B Homework 2 Wiki

Section 1

  • When the extrinsics are the same, how will the distance of the pixel coordinate from the optical center change for a given point when you double the focal length? - The first problem asked the changes for the distance from the optical center on the image plane to the point that the same point in 3D imaged.
  • Given 10 known points for a calibration object with a distortion-free camera, how many images are required to calibrate the camera? - Please assume any three points are not linearly aligned.
  • MacOSX OpenCV Install - Has anyone got this to work? I am able to get through the ./configure, make, and make INSTALL stages without any trouble. When I try to run any of the sample programs, i get errors for all of the OpenCV specific calls being outside of the declared scope.

MacOSX OpenCV Install: Assuming you have all the libraries installed (you can do them by either Fink or MacPorts), and if it is working fine till make install stage, what you want to do is enter the following commands in the command line (or add them in you bashrc file):

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig export LD_LIBRARY_PATH=/usr

and then use the command g++ -bind_at_load `pkg-config --cflags opencv` hw2.cpp -o hw2o `pkg-config --libs opencv` to compile a file hw2.cpp which outputs hw2o.

For more reference on installing OpenCV for Mac, http://wiki.nuigroup.com/Installing_OpenCV_on_Mac_OS_X.

Section 2

  • Why are we using 11 images?- You need more number of images than mentioned in class because the object is planar. Also, the more images you have, the more closer you are to actual camera parameters. Remember, there is always noise in measuring the pixel coordinate, etc.
  • Why are some of the functions mentioned not found in OpenCV Wiki? - The functions listed in assignments are just examples. Actually, those in handout are older version compared to functions listed in OpenCV Wiki. You may use any of those, and you are supposed to get a very similar result in either ways.
  • The cvDrawChessBoardCorners() function now draws lines connecting each point in sequence in addition to circles around each found point, is this ok for the pictures we turn in? - Yeap.

Section 3

  • Do we have to calibrate a cell-phone camera per se, or can it be a webcam or some other digital camera?
Retrieved from "http://cs223bwiki.ethandreyfuss.com/wiki/HW2_FAQ"