I only skimmed it, but looks like they track midpoint of eyes (having rejected pupil tracking), and spacing (to get viewer distance), and they use a webcam to do it.
That's what I read too.
The reason I asked is because "either the distance on the first frame for the case interface : False or the distance when the set depth button is pressed for the case interface : True" is not entirely clear to me.
When I was working on such a project, I had no way of correctly guessing the distance between the screen and eyes.
When I was working on such a project, I had no way of correctly guessing the distance between the screen and eyes.