Which way is up after using mne.preprocessing.eyetracking.convert_units to convert screen coordinates?

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1

We know that EyeLink trackers defaults to setting (0, 0) as the top left corner of screen, with positive Y values referring to areas below it

and MNE defaults to using screen centre as (0, 0), but what about the Y-axis orientation? Where does the positive values point to?

In the document here
Plotting eye-tracking heatmaps in MNE-Python — MNE 1.12.1 documentation
after conversion using mne.preprocessing.eyetracking.convert_units with pix_to_rad option, the example showed a flipped Y-axis with positive values pointing up and negative values pointing down

But this feature doesn’t seem to reflect in the source codes at
mne-python/mne/preprocessing/eyetracking/eyetracking.py at maint/1.12 · mne-tools/mne-python?

This is a bit too confusing for me

2

That’s a good question, perhaps plotting the stacked time series here before and after unit conversion will help us confirm your observation that the y-axis orientation of radians-of-visual-angle is flipped as compared to pixel-on-screen-data: Importing Data from Eyetracking devices — MNE 1.12.1 documentation

E.g. you can do ipython -i tutorials/io/70_reading_eyetracking_data.py from the MNE-Python repo root if you have ipython installed, to get the script running in an interactive environment. I can look later but don’t have the time right now.