8

Setting Joint Parameters 465
Cleari ng K eys from Previous Animation
If you have animated any members of the IK
chain inter ac tively, or run Apply IK previously,
the existing animation keys will affect t he new IK
solution. Sometimes that is exactly what you want.
You can use manual animation to subtly nudge the
IK solution toward a particular result. However,
it is more likely that you want to remove old keys
in order to begin the IK calculations with a clean
slate.
TheClearKeysoptionintheInverseKinematics
rollout controls whether or not old move and
rotate animation k eys are removed.
Constrai ning the
IK S olution to Specif ic Frames
You use the Start and End fields in the Inverse
Kinematics rollout to set the range of f r ames used
to calculate the applied IK solution. Using these
fields, you can restrict IK solutions to specific
frames and solve for different solutions in different
time segments.
You can set the Start and End fields to include
frames outside of the active time segment.
You can also constrain an IK solution to fr ames
where a key exists for an end effector. This is
useful if you want to animate a hierarchy using end
effectors but do not want keys generated on every
frame.
TurnonApplyOnlyToKeystoconstraintheIK
solution to fr ames with end effector keys.
Watching Progress of the IK Soluti on
N ormally, Apply IK calculates all frames before
updating the viewp orts. To watch the progress
of Apply IK frame by frame, turn on Update
Viewports on the Inverse Kinematics rollout.
Updating the viewp orts greatly slows down the
ApplyIKprocessbutitcanhelpyoutroubleshoot
complex animations.
Joint Controls
Setting Joint Parameters
You set whether a joint behaves as a hinge, a drawer
slide, or another type of joint by setting
joint
parameters (page 2–440)
for each object in the
kinematic chain. Joints control the rotation and
position of an object with respect to its parent.
Any object has a maximum of two joint-type
rollouts: One rollout contains settings to control
the object’s position, and the other controls the
object’s rotation. There can be many different
types of positional and rotational joints. Which
joint parameters are available is determined by the
type of IK solver assigned to an object. HI Solvers,
for instance, are controlled with a preferred angle
setting found in the Rotational Joint parameters.
HD Solvers have additional parameters for spring
back, precedence, and damping, not found in the
HI S olver.
Any hierarchy of object or bone systems can ha v e
its joint limits defined. Select all the objects, and
turn on their bone or link display. Selec t the
bone or link and open the Hierarchy panel > IK
tab. Scroll down to the Sliding and Rotational
Joints. There, you can activate a xes a nd set their
individual limits.
Note: Different IK solvers use different joint limits.
When using a bone system, add the IK solvers first,
thensetthejointlimitssecond.