How can I detect eye contact/mutual gaze between two people in a video using the gaze vectors?

[amritbhat786]

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Additional context Will the gaze vector (X,Y,Z) of one person be the negative of another, if they are looking at each other? Can this logic be used to detect mutual gaze/eye contact?

[brmarkus]

These would "just" be two vectors, "representing" two lines in a 3D space (or, projected, in a 2D space); these could be parallel, could cross each other, could be exactly the same, could be "mirrored". But whether they really have eye contact is difficult to say, isn't it?

[amritbhat786]

Thanks for your comment, @brmarkus. Can't we say that if the gaze vector (X,Y,Z) of one person is the negative of another, they are having an eye contact?

[brmarkus]

If the two persons stand next to each other, shoulder-at-shoulder - then their gaze-vector could be "opposite", yes, the negative of the other, but their vector might just be parallel - shoulder-at-shoulder or a few meters between them, looking just parallel... not necessarily looking into their eyes.

[brmarkus]

This is about whether two lines in 3D space (given by two vectors, but without a "base") intersect, e.g.

https://math.stackexchange.com/questions/302598/how-to-prove-that-two-lines-in-3d-are-not-parallel-and-do-not-intersect-also-h

https://mikespivey.wordpress.com/2016/10/06/how-do-you-tell-whether-two-lines-intersect-in-3d/