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Open Sesame Output - variables eyeposition x/y/z missing

Hi guys,

I recently decided to use Open Sesame along with our Tobii TX-300 Eyetracker to perform a antisaccade paradigm. So far, everything works fine. I just have one major issue I need to resolve:

The output-file from Tobii only contains gaze-points on the display and pupil size for left and right pupil. To calculate reaction times from the central cue to the target cue, I would also need the eye-position from each participant in the room (x, y, z coordinates) - I couldn't find any possibility to change the output. Is there a solution for this?

Thanks for your help in advance,



  • Hi,

    I think one way to change the Tobii log-file is by actually changing the in Pygaze package. In this way you can control what is written in the log.

    You can find this file in you OpenSesame folder, under \Lib\site-packages\pygaze\_eyetracker\

    However, I recommend making a copy of the original before making changes.

    My guess is you need to change the following lines, and add your variables:

    self.datafile.write('%.4f\t\t%d\t%d\t%d\t%d\t%d\t%d' % (

                               (sample['system_time_stamp'] - self.t0) / 1000.0,







    Hope this helps.



  • Hi Paula,

    thanks for the hint, very helpful!

    Do you know if there is a list of all available variable names? I'm a bit confused with the wording of the variables as they are different in Tobii Pro Lab than in the file, and I guess it's necessary to name them same as the eyetracker does itself. For example there is GazePointXLeft in the logfile as one column, but in the lines self.datafile.write there is the wording left_gaze_point [0] / [1]. If I want to add Eye Position Left X/Y/Z, do I need to put a line with left_eye_position [0] / [1] / [2] to the self.datafile.write (its three dimensions)?

    Thank you, Alex

  • Hi Alex,

    Sorry, but I can't help you further. I don't know the variable names... Your intuition looks correct, though.

    All the best,


  • Hi,

    What Paula says seems to make sense, but in addition to changing the variables you want to log, you also have to change the names you give the columns. The piece of code above, only describes how additional lines are added to the files, not how the file is set up. I don't have a tobii, so don't know where this would be needed to be done, but maybe it will be helpful to you.

    Good luck,


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