I wouldn't be surprised if it's some form of (a variant or advancement) of FACS which we've used in animation eons ago https://en.wikipedia.org/wiki/Facial_Acti

I wouldn't be surprised if it's some form of (a variant or advancement) of FACS which we've used in animation eons ago https://en.wikipedia.org/wiki/Facial_Action_Coding_System https://en.wikipedia.org/wiki/Facial_Action_Coding_System Basically for each of the identified poses you have a key and you grab a pose of it (photogrammetry here) and then you would capture performance and identify somehow which combination of keys and weights would be translated to you model. Sounds easy but it ain't.