Engagement is based on 4 elements: F1(Pupils), F2(Head), F3(eyebrow), F4(Mouth),
based on the calculation Engagement = .26F1+.11F2+.3F3+.19F4
F1 infers positive engagement when pupils are in center or right.
F2 when head is in center.
F3 when eyebrows are up or down.
F4 when mouth is in center.
How to decision F1~F4?