2009

■ The second chain is created from the ankle to the ball of the foot. This
chain controls the heel's up and down motion.
■ The third chain is created from the ball of the foot to the toe.
When the three chains work together they help to maintain the foot’s position
in space. This means it will keep the foot planted on the ground as the
character’s body moves. All three IK chains in this hip-to-toe setup place goals
at key positions in the foot that mimic natural foot behavior. In real life, the
toe, ball of the foot, and heel can be planted on the ground or raised.
Each chain has an goal that drives motion on the heel, ball of foot, and toe.
Use the IK goals to raise the heel, bend the toe, move and rotate the entire
foot, and maintain the foot's position in space.
Overlapping Chains
The IK solver system allows you to create overlapping IK chains in a single
hierarchy. In a human leg, for example, you could create a chain running
from the hip to the ankle, then a second chain from the knee to the ball of
the foot, and a third from the ankle to the toes. Use overlapping chains, when
you want to apply goals to sequential bones, but you don't want to refine the
bones.
Another good use for overlapping HI IK chains is to keep the goals at the
bottom of the hierarchy firmly rooted in place. In the case of the leg example,
the ankle, ball and toe of the foot would not move until the upper portion of
the hierarchy had reached its full stretch.
Inverse Kinematics (IK) | 3393