Is your feature request related to a problem? Please describe.
I would like to use a movement function like compute_forward_vector_angle to compute forward_vector starting from rear and front points instead of left and right (in my case, from the bottom I have reliable neck and nose positions but no left and right ear positions).

Maybe I'm missing something stupid? But all functions in orientation seem to refer to left and right keypoints, no?

Describe the solution you'd like
compute_forward_vector(..) to accept back and front points instead of left and right

Describe alternatives you've considered
This is simple to compute outside movement of course, but would be nice to do it within as well for consistency with other variables computation.