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How do I determine if a person is looking at the screen?

17 Jul 2020

First, let me say that visage|SDK does not have an out-of-the box option to determine if the person is looking at the screen. However, it should not be too difficult to implement that. What visage|SDK does provide is:

• The 3D position of the head with respect to the camera;

• The 3D gaze direction vector.

Now, if you also know the size of the screen and the position of the camera with respect to the screen, you can:

• Calculate the 3D position of the head with respect to your screen;

• Cast a ray (line) from the 3D head position in the direction of the gaze;

• Verify if this line intersects the screen.

Please also note that the estimated gaze direction may be a bit unstable (the gaze vectors appearing “shaky”) due to the difficulty of accurately locating the pupils. At the same time, the 3D head pose (head direction) is much more stable. Because people usually turn their head in the direction where they are looking, it may also be interesting to use the head pose as the approximation of the direction of gaze.

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