How does the eye opening calculated?

[desti-nation]

In Face.py

ud = left_eye_upper-left_eye_lower
ex = left_eye_upper1-left_eye_upper0
ex /= np.linalg.norm(ex)
ey = np.cross(np.array([0,0,1]),ex)
left_eye_opening = np.dot(ud,ey)

May I know what is the meaning of the above code?

[ParisNeo]

Hi,
A simple straightforward way to do this is simply compute the norm of the vector going from the center of the lower part of the eye to the center of the upper part. But mediapipe's markers are not exactly centered. They are centered on the bottom but not on the top.

On the top, there are two markers that form a straight line. upper1 and upper0. so I compute the center that i call upper (just (u0+u1)/2 . Now I can compute the up down vector ud by just doing the difference.

The rest of the operations are not mandatory. I just rebuild a 3d reference aligned with the eye and project ud on its y axis.

First I build the left right vector ex, then I normalize it, then by doing a cross product with 0,0,1 i get the unit vecor ey which is a vector perfectly perpendicular to the left right vector of the eye. Finally I project ud on that vector nd get the eye opening.

It enhances slightly the results. But I think I can dig into it firther.