Maya 4.5 Fundamentals

Character animation means applying anthropomorphic motion to objects. These objects don't necessarily need to be human or animal characters. Virtually anything can be a character gas pumps, mushrooms, and even sacks of flour have been animated as characters. However, in nearly every case, the animator uses deformers in Maya to impart animal motion and intelligence (and, if the animators are successful, emotion and identity). Obviously, you can animate robots and other rigid objects in a way that still conveys they are characters. This chapter, however, is concerned with organic, bendable characters.

Deforming objects in a way that mimics nature is usually more complex than other deformations in Maya. Typically, if you're bending or twisting something, you can add the deformer and quickly get the mechanical result you want. However, animating something with an implied skeleton overlaid with muscles, which are overlaid with skin, which is overlaid with clothing, requires a lot more adjustment to get an anatomically believable result. For example, a human elbow bends differently than a neck joint does. Initially, all of your Maya joints allow universal rotation. Further, real muscles "flex" when contracted, creating a bulge as the muscle tissue is compressed an effect that's more evident for some muscles than others. Also, localized joint movement pulls and relaxes nearby skin in varying ways. A torso doing a "crunch" makes skin do something different from the skin on fingers bending into a fist. Finally, all these variations are different from character to character; a scrawny old wizard is set up quite differently from a plump baby or a bodybuilder.

The general approach in this chapter is to first create joints inside the character to provide articulated movement so that you can animate the character. Usually, you add joints only where you want to bend the character, so a shoe-wearing character doesn't need toe joints for each toe. Next, these joints are connected to create a complete linked skeleton and adjusted to fit properly within the areas they will deform. Note that the joints themselves are not rendered, so if a joint protrudes through part of the character, it doesn't necessarily require adjustment.

Next, Inverse Kinematics (IK) is applied where needed, usually to each link chain that connects to the root joint. On a typical biped, the arms, legs, and spine/head are connected with IK so that you can make the character crouch by simply pushing the head down. To ease the animation process, easy-to-select handles are created as part of the character rig.

With the skeleton now behaving in a controlled manner with IK, the character geometry is then bound to the skeleton as a smooth or rigid bind. The procedure from here varies depending on the type of binding, but the goal is to get muscles to flex and joints to bend in the way you want. In this chapter, you use rigid binding, which leads to using flexors to adjust local joint bends.

With the character set up for animation, you can set keys to make it move. In this chapter, you set the character to take a couple of steps forward. With IK already applied, simply adding key poses to the hands and feet make the rest of the character move appropriately.

Maya's Trax feature enables you to take any motion set from a defined character and apply it as a "clip." You explore this feature by using a single walk cycle to make the character walk for some distance.

Finally, you explore facial animation with Blend Shapes. Starting with a neutral face, you sculpt a new facial pose and then blend this pose with the neutral pose over a period of time.