Hi Chris,
We’re running into an issue with the eye data in our setup. As you know, we’re sending all data to Blackrock and reading everything from the Blackrock files. When we load and plot eye X and Y, the units aren’t clear, they’re neither in visual degrees nor screen (pixel) coordinates.
It seems that MWorks is sending calibrated eye data, but it’s transformed in some way. For example, (0,0) corresponds to the fixation point at the center of the screen, but the X and Y values range around ±5000 in the saved data. We’re not sure how to convert this to screen gaze or visual angle coordinates.
Please let me know if you need more information.
Best,
Ahmad
Hi Ahmad,
Every datum you send to Blackrock has to be encoded as an integer between 0 and 65,535. Calibrated eye coordinates are floating-point numbers in degrees of visual angle. To send them to Blackrock, you have to map them to integers somehow.
This mapping isn’t done by MWorks. It’s performed by your experiment code, presumably whenever the eye data are transmitted. To interpret the eye data as stored in a Blackrock file, first look to see how your experiment is mapping the floats to 16-bit integers, then perform the inverse of that mapping on the stored values.
Cheers,
Chris
Hi Chris,
Thanks so much for the clarification. Really appreciate your help!
Best,
Ahmad