Human Facial Animation: Enough Ideas: (1) The Skull structure While the human skull has only one joint (the jaw) it certainly has more bones. These bones anchor the skin in areas that lack muscles, and also add rigidity to the face in certain areas, like the nose and the cheekbones. Since in Softimage/Sumatra other objects can be IK bones, ItÕs easiest to create a large sphere for the main area of the skull, with a smaller sphere inside the mouth cavity. This lower sphere will give volume to the mouth. It should be constrained between the four other cheek muscles so it floats up and down with expressions and jaw movements. It also has an expression on it that thins it out as the jaw drops, hollowing out the cheeks. The last important bone is the nose ridge. Without a rigid nose, the character would have a rubbery face. The nose anchors the muscles on either side of it, which can be constrained between it and the jaw. In addition to these, it is often helpful to add in a small sphere near the forehead region, and another to the base of the skull near the back of the neck Together, these rigid objects give structure to the head, and make weighting points easier.