The goal of rigging is to make it as direct and easy as possible for the animator to do the job. Ideally, the character needs to be animated as fast as the animator can think. This might seem to be a daunting task
A good character rigger is part animator, part programmer, and part interface designer. The rigger needs to understand how animators work and translate that into an efficient setup. The perfect setup allows animators control over the character while automatically managing the parts of the character that the animator does not need to think about.
When rigging a character, the first order of business is to get the skeleton working. The goal is to make the character easy to manipulate for the animator.
Grab Points and Handles
Skeletal animation is much easier when you make it simple for the animator to easily select parts of the character. This is typically done by creating null objects that are placed as handles or grab points for the animator to use in manipulating the character. In stop motion, a grab point is a hard point on a clay character that allows the animator to grab and move a joint without seriously deforming the clay. Grab points are used on digital characters as well, but in a slightly different context.
The feet and legs are a good example of where grab points come in handy. If you wanted, you could simply use the IK handles created by the software to manipulate the legs. These handles, however, are usually buried within the character's mesh and can be hard to locate, as Figure 1 shows. To make it easier on the animator, you can create a grab point that is outside the mesh and easy to find, like the one shown in Figure 2. Moving the grab point, in turn, will move the IK handle.
Figure 1 With the skeleton buried under the mesh, it's hard to see the ankle, much less select it.
Figure 2 Creating a grab point outside the mesh makes it much easier to select the ankle.