They mention how they do that if you RTFA, fwiw.
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.
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.
When I was working on such a project, I had no way of correctly guessing the distance between the screen and eyes.