2009

moves the pivot point of the wrist, called an end effector on page 7963, toward
the goal.
In the case of a leg, for example, the foot is constrained to the floor by the
goal. If you move the pelvis, the foot stays put since the goal has not moved,
and this causes the knees to bend. The entire animation is contained in
keyframes for the goal and the root, without keys being applied to the
individual chain objects.
With inverse kinematics you can quickly set up and animate complex motions.
The basic procedure involves these tasks:
■ Build a model. It could be a jointed structure or many pieces or a single
continuous surface.
■ Link the jointed model together and defining pivot points, as described
in
Hierarchies on page 3331.
For a continuous-surface model, create a
Bones on page 901 structure or use
a biped to animate the skin of the character.
■ Apply
IK solvers on page 3382 to the jointed hierarchy. You will probably
create several IK chains throughout the hierarchy, rather than just one.
You might also create several independent hierarchies, rather than link
everything together in one large hierarchy. For simple inverse kinematic
animation you can use interactive IK, without applying any IK Solver.
■ Define
joint behavior on page 3466 at the pivot points, setting limits or
preferred angles, depending on the type of IK solvers you are using. Here
you can set up sliding joints or rotating joints.
You might also need to move the root of the hierarchy, and you might
want to add control objects such as dummies or points at this point.
■ Animate the goal (in the case of an
HI Solver on page 3392 or IK Limb solver
on page 3444) or the end effector (in the case of the HD Solver on page 3422).
This animates all the components of the IK chain.
You can apply constraints on page 3287 to the goals or control objects or to
the root of a chain.
You can externally reference IK chains in your scene. An XRef IK chain behaves
the same as a non-XRef chain, except that you cannot retarget its
XRef
controller
on page 3269 once it is in your master scene. For more information,
see
XRef Objects on page 6936.
Inverse Kinematics (IK) | 3375