I had the opportunity during pre-production on Epic to work closely with some of the Riggers at Blue Sky. After the characters are modeled, the Riggers add all the manipulators that the animators will need to control the characters and achieve the best performance. Our role as animators during pre-production is to evaluate the rigs and communicate to the Riggers anything that we might need during the course of production. I would use Photoshop to give the Riggers a visual targets for what we were trying to achieve. The painting above was a suggestion for how the extreme "cheek puff" shape should look on Nim Galuu. The painting below was a suggestion as to how the generic Leafman's elbow geometry should deform when the arm is bent. The elbow on the left is the starting point without any blend shapes added. The image on the right are my paint-overs.