Eye tracking: Difference between revisions
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The experimental sort of eye tracking usually | The experimental sort of eye tracking usually | ||
* illuminates the inside of the eye with near-infrared | * illuminates the inside of the eye with near-infrared | ||
* IR camera that | * IR camera that is zoomed in to look at just the eyes | ||
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Now rotate your head and keep looking at the same spot. | Now rotate your head and keep looking at the same spot. | ||
Your pupils are moving from left to right | Your pupils are moving from left to right within your eye sockets -- yet the place it should detect does not move at all. | ||
From ''just'' the image of the pupil in the eye, you would not get a halfway decent direction. | |||
We can fix that by fixing your head in place, and while "please rest your chin here" is fine, | |||
"please allow us to clamp your head in place"... makes people not like you much. | |||
Another fix to this is to also track the cornea. | |||
Corneal-reflection-style eye tracking (there are others) adds a reference. | |||
That reference is the back of the eye. It is also free to move but, being (roughly) spherical, | |||
whatever the backmost part of the eye is (which is the part that will reflect), | |||
the place of most reflection will barely move when the eye looks around, | |||
so it acts as an anchor. | |||
This definitely still has limitations, but is also a good step less janky than just pupil. | |||
"Can't you add, I dunno, 3D head tracking?" | "Can't you add, I dunno, 3D head tracking?" | ||
Yes, and that | Yes, and that can help, but at the same time also adds assumptions to the whole, as well as another limited-accuracy thing . | ||
"Can you do this with a webcam?" | |||
At all? Yes. | |||
Accurately? No. | |||
You can download an app for your phone right now. And its output will be... not great. | |||
Why? Multiple reasons | |||
'''"Could I do this with an IR-sensitive webcam?"''' | |||
...plus an IR illuminator? | |||
It would work better than just a webcam, but still not great. | |||