particle-painting techniques
So the trick was making the in-game tool powerful while remaining accessible to those who lack the artistic expertise of an industry professional.
retargeting
inverse kinematics
Evolutionary Chain
http://www.cgw.com/ME2/dirmod.asp?sid=&nm=&type=Publishing&mod=Publications%3A%3AArticle&mid=8F3A7027421841978F18BE895F87F791&tier=4&id=CDC428C4E9E54710A564B55B6277608A