Using Tissue System
Click the Tissue System tool on the Muscles shelf.
If you are including franken muscles, do not select the individual components. Only include the franken muscle itself.
Select the skin object you want to include in your simulation. The skin object will be converted to tetrahedrons and should enclose the internal muscles and bones. It is assumed that the bone geometry has been previously animated via standard bone capture methods. Therefore, all geometric bones are likely to be selected as a single object.
Select the skeletal bone objects. If you don’t have any bones, press Enter.
These are the modeled, anatomical bones, not IK/FK bones. These objects will act as rigid colliders against your muscles and skin.
The Tissue System shelf tool will create a new object that will house the collected items as well as the output of the simulation. The muscles must be tetrahedrons, so they should come from muscle or franken muscle objects. Muscles and franken muscles have specially named hooks, so these components can be found by the Tissue System. If you wish to include other geometry as an internal component to the system (such as fat), you must convert this geometry into a franken muscle first. Bone geometry can be sourced from any geometry as it will be converted inside the tissue solver.
The character on the left has its skin deformed using muscles as a displacement deformer, whereas the character on the right has its skin deformed with the Tissue System tool. The underlying tissue solve of the character on the right helps create more realistic creases and bulges along the character’s back and gives you very physically accurate results without any artist intervention.