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444 Chapter 12: Animation
These settings are found on the Link Display
rollout on the Display panel. This c an be useful
if you have a geometrically intensive hierarchy
to animate. The interactive viewport response is
faster when the geometry is hidden and displayed
only at links.
Advantages of Animating Bones with IK
It is possible to animate a char acter’s motion
through forward kinematics, rotating each limb
into position from the shoulder to the fingers, and
the hips to the toes. But it’s a lot quick er and more
realistic to use i nverse kinematics to simulate the
foot interacting with the ground. And it is a lot
easier to control when you need to make changes
to the animation. Rather than ha ving keyframes
on every bone in the chain, you have to make
changes to only one node, to change the animation
oftheentirechain.
On the other hand, it is common for animators to
useIKforthelegsandFKforthetorsoandthe
arms. FK offers a bit more control for posing the
upper b ody. It is not necessary to use IK for every
character animation task. Using the HI IK solver
allows you to jump back and forth easily between
FK and IK.
How to Apply an IK S olver
YoucanapplyanIKsolverwhenyoucreatea
Bones system, or from the Animation menu:
• Bones creation (page 1–404)
When you create bones, turning on the Assign
to Children option lets you apply an IK solv er
immediately. Default=Off.
• You can apply the IK solver to a part of the
skeleton using Animation menu > IK Solver.
You must select the node where you want the IK
chaintostart,thenchooseAnimationmenu
> IK Solvers and select the solver. Then click
the node where you want the chain to end . The
chain will b e c reated between the pivot points
of the two nodes. If you are using an IK Limb
Solver, the IK goal will be placed two bones
down from the highest no de you’ve selected in
the chain.
Where to Adjust the IK S olver
Yo u a d j u s t I K s o l v e r s e t t i n g s i n t h e M o t i o n a n d
Hierarchy panels:
• Motion panel (page 3–774)
When the goal of an IK chain is selec ted, the
motion panel displays the rollouts for the
individual IK solver.
HI S olver —Motion panel parameters adjust the
swivel angle (page 2–449) of the solver plane, to
point the knees and elbows. Also, the controls
in the IK Solver rollout let you mix periods of
IK w ith FK (forward kinemat ics) through the
Enabled button and the IK button.
HD Sol ver—Motion panel parameters assign,
remove, and edit the end effector for the
currently selected joint. You can parent the
end effector to another object, and return
the skeleton to an initial pose. Changing IK
controller parameters in the Motion panel
affects the entire HD IK chain, even when
you’ve selected only a single bone.
IK Limb Solver—Motion panel p ar ameters for
theIKLimbsolverarethesameasfortheHI
Solver.
Spline IK Solver—Motion panel parameters
allow you to activate/deactivate the solver ,
adjust the bones assigned to the start and e nd
joints, adjust start and end twist angles and
make twist handle display settings.
• Hierarchy panel (page 3–773)
HI Sol ver—When a bone is selected, the IK
panel displays controls to activate and limit the
rotational joints, and set a preferred angle for
the j oints. The preferred-angle poses of all t he
joints help control the direction of rotation of