Brain Imaging & Analysis Center

The EYE_FLAG parameter is used as an argument to the R_EYEPOS real-time function to specify options when reading streaming eye position data input. The parameter is an integer bit-flag variable, in which each multiple binary values can be combined by addition. The meaning of the individual flag bits are as follows:

• 1 EYE_XYPOS – enable eye position (X,Y) measurements
• 2 EYE_PUPIL – enable pupil diameter (XSIZE,YSIZE) measurements
• 4 EYE_READ – read eye-tracking data
• 8 EYE_DEBUG
• 16 EYE_SCREENSCALE
• 32 EYE_WAIT
• 64 EYE_PURGE
• 128 EYE_DRAWPATH – draw eye position scan path on screen
• 256 EYE_REPLAY – re-use stored EYEVALS and EYETIMES data
• 512 EYE_NOWAIT
• 1024 EYE_MOVECURSOR – move cursor arrow as eyes move

The default value for EYE_FLAG is 0. A typical EYE_FLAG value for recording eye position and pupil diameter is:

eye_flag = 01007o   (519 decimal)

The EYE_REPLAY option is typically used in combination with EYE_DRAWPATH to display stored eye movement data on top of the stimuli. For this to work properly, the EYETIMES array variable must contain time-stamp values in 20 us clock tick units, relative to time 0 (task onset). Thus, when reading stored EYEPOS and EYETIMES data from a CIGAL paradigm file for replaying, the LTIME0 parameter found in that paradigm file must be subtracted from all EYETIMES values before replaying. If eye data is reloaded from text files where times have been converted to units of seconds, EYETIMES values are already relative to task onset but will need to be scaled (by 50000) to convert to 20 us units.

Note: To record eye-tracker data you must first initialize the eye-tracker hardware and software connected to a different computer, and then also initialize CIGAL's eye-tracker connection to that computer (see Eye-Tracker).

See Also:
Initialize, Eye-Tracker

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