Our skinny man. In the 3DbyBuzz tutorials we looked at the Maya skeleton generator, and at doing a soft bind of our skinny man to the skeleton. We stopped there, but there is more that we could do, and there will be posts in this blog in the future covering these techniques. Here he is:
This posting is a preview of what we can do to create a more organic, natural looking binding. The key is to simulate the varying sorts of tissue that lies beneath our skin. These include muscles, bones, and joints. What’s wrong? Our character is far from natural looking. With respect to hardness, he appears to have completely homogeneous tissue. He’s a rubber man. Real people have muscles, along with solid bones, both of which can be seen beneath our skin. The Maya muscle system. All of this can be simulated by use the Maya muscle system. The muscle system can be accessed by setting the Main Menu Selector to Animation, and then going to the Muscle dropdown on the Main Menu. Capsules. Maya has something called “capsules” which are rigid and can be used to make a joint appear solid. Keep in mind that joints themselves do not have any geometry, and so we use capsules to make it appear that a joint has actual geometry. We can convert joints to capsules. Bones. Maya also has “bones” which serve a very similar purpose, and are created from polygon geometry, and so their shape can be carefully controlled by the animator. (These bones have nothing to do with the bones that get laid down between joints as we build a skeleton.) Like capsules, bones can be created by conversion; we turn joints to bones. Muscles. In Maya, bones and/or capsules are used to create “muscles”, which are attached beneath the surface of your character’s skin. They will cause the skin to deform. Each muscle is connected in two places (to capsules and/or bones), and when the limb is extended, the two connection points will move apart and the muscle will extend itself. As the limb is closed, the two connection points will move closer and the muscle will bulge outward. It’s not trivial to use. The Maya muscle system is difficult to master and calls for a lot of iteration. One thing to note is that making a smooth binding look realistic by inserting muscle tissue is a complex problem. Muscles are not completely rigid. They are semi-rigid, and not all muscles extend and bulge in the same way. Muscles also move as coordinated groups as the human body moves. All the while, the skin moves over the muscles in a semi-independent fashion, but it does not float freely over the underlying tissue. Cloth. Finally, there is some similarity between muscle/skin/bone systems and the sorts of movement that can be engineered using blend shapes and/or cloth.