Sunday, October 24, 2021

Facial Action Coding Systems and Model Typology

From my facial rigging class, one of the concepts I learned is that it's very hard for humans to isolate the muscles in the face because of how they are so inner connected.  When you move one part of the face, other muscles on the face move and react too.

AU - Fundamental actions of individual Muscles or groups of muscles.

AU - Brows: These are just very basic

  • Inner Brow Raiser
  • Outer Brow Raiser
  • Brow Lowerer - This is the only action that brows do apart from inner and outer
AU - Lips
  • Upper Lip Raiser - Raises the upper lip corners
  • Lower Lip Depressor - lowers to lower lip corners
  • Nose Wrinkler - compliments upper lip raiser expressions.. It moves the corner of the nose and creates a deepening in the nasal fold.  
AU - Mouth
  • Lip Corner Puller - Basically is a smile
  • Lip Corner Depressor - Frown or Sad
  • Lip Tightener
  • Lip Stretcher

Facial Rigs are controlled through attributes or controllers.  The danger with attributes is that the animator will have to know what to reduce or increase to get the facial expressions they are looking for.  Controllers do a better job at fixing this problem where animators need to adjust many different attributes.  Having controllers may give you more control to follow the action units.  Both attributes and controls give you the action units you need.  


AU - Cheeks
  • Cheek Puff - Inflates
  • Cheek Suck 

Awesome Web Reference: Imotions


 Typology:

Typology on a model is key to get good results on both the shapes you create and the deformation.

Before you start rigging, you should always check the typology.  If you are modeling it or receiving it, it's always a good idea to check it. 

Things to look for in good typology:
  • Circular loops in the mouth and eyes
  • same number of edges on upper and lower lips and eyelids
  • Quads
    • Proportional and even
    • Good flow
    • Triangles if needed out of the way
    • star edges out of the way as much as you can
  • Vertical edges on eyebrows
  • Muzzle loop
  • Nasolabial Fold Line
Example from Google of Facial Typology


Good website for typology reference: Hippydrome

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