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ShowPlay Reference Manual, Chapter 7 (Programs): eyecalib

Eyecalib -- Calibrate the eye-tracker hardware interface

usage: eyecalib flag nxpts nypts pctX pctY nbox boxwid imagefile color
or usage: eyecalib 8 eyecalibfile

The EYECALIB command is used to calibrate eye position on the screen using a matrix of NXPTS x NYPTS locations (default is 5×4). During the calibration, the subject should simply look at a box that appears at a series of different screen locations. At each location, the displayed image will shrink to a point, and the subject should fixate on the center of each box until it disappears.

If the subject can not see the whole screen, or will not need to look at the whole screen, you can use pctX and pctY to indicate what fraction of the screen you want to calibrate. The default values for PCTX and PCTY are 95% x 95% of the screen, horizontally and vertically. If you use the EYECALIB command via CIGAL's standard menu interface (Settings → Calibrate EyeTracker), EYECALIB will be called with PCTX and PCTY set to a smaller screen region (e.g. 70% x 60%).

The FLAG argument controls various calibration options. Most options can be combined by adding values. Note that FLAG option 8 is unusual and does not result in the normal calibration display. The FLAG options are:

   0 - normal mode
   1 - scramble the order of display positions
   2 - don't preshow start location
   4 - don't erase locations
   8 - recalculate matrix from existing eyecalib file
       With this option, the second argument can be used to specify the filename
       (instead of NXPTS). If you do not specify a filename, you will be prompted 
       to browse to find the calibration file.
  16 - don't display eyepos plot
  32 - save eye calibration raw data in text file
  64 - no delay between locations
 128 - save calib tables in eyecalib file
 256 - don't create eyecalib file

By default, FLAG is 0, which results in the calibration box being shown in successive locations, and after all positions have been displayed, the calibration points and recorded eye points will be displayed, and the recorded values will be saved in a CIGAL data file. The output data file is named “eyecalib_X”, where X is a number that ensures that new data will not overwrite other calibration files. The “eyecalib” files are written using the CIGAL DMWRITE command. (The FLAG 32 option would cause a plain text version of the calibration data to be stored as well.)

The NBOX and BOXWID arguments are used to the appearance of the disappearing box. By default those values are NBOX=5 and BOXWID=40, which results in 5 concentric boxes where the outermost box is 40×40 screen pixels.

The IMAGEFILE option lets you provide an image of your own to use instead of a disappearing box display. If IMAGEFILE is a valid image file name, that image will be displayed at each position, and then gradually shrink in NBOX steps.

The COLOR argument lets you specify the background RGB color for the calibration screen. The default color value is 08e8e8eh (gray).

Note: After running EYECALIB, the eye calibration tables (EYE_SCRPOS and EYE_EYEPOS) generated by this command are also automatically saved in any Showplay PDIGM File output files created later in the same CIGAL session.

See Also:
Eyetracking, Eyetracker hardware, Eyecalmap, Eyecalproc, Eyecalwks.

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jvs/cigal/showplay/manual/chapter7/eyecalib.txt · Last modified: 2023/02/23 18:43 (external edit)