8

450 Chapter 12: Animation
Precedence—
Sets joint precedence manually.
Child->Parent—Automatically sets joint precedence
to decrease in value from child to parent.
Parent->Child—Automatically sets joint precedence
to decrease in value from parent to child.
Determining Or der of Calcula tions
You control the HD IK solution by setting joint
precedence to determine which joints contribute
the most to the H D IK solution and which joints
contribute the least.
• Jointswithhighprecedencevaluesare
calculated first, and contribute more motion
to the HD IK solution.
• Joints with low precedence va lues are calculated
last and contribute the least motion to the HD
IK solution.
• Joints with equal precedence values are
calculated by order in the hierarchy. Joints
closer to the end effector are calculated first and
joints closer to the root are calculated last.
Of all of the joint parameters, Joint Precedence is
the most subtle.
See also
Using Default Joint Precedence (HD Solver) (page
2–450)
Choosing Child-to-Parent Precedence (HD
Solver) (page 2–450)
Choosing Parent-to-Child Precedence (HD
Solver) (page 2–451)
Setting Precedence Manually (HD S olver) (page
2–452)
Using Default Joint Precedence
(HD S olv er)
Thedefaultjointprecedenceissuitableformany
HD IK solutions. It assumes that joints closest
to where a force is applied (the end effector) will
move more than joints farther from the force.
Thedefaultjointprecedenceisavalueof0for
every joint:
all joints have the same precedence
value
. This default starts calculations with the end
effector and progresses up the IK chain until the
base object is reached.
Using methods described in t he following topics
you can change the default precedence values.
You can also set your k inematic chain back to its
default precedence.
To r eset the def a ult j oint precedence:
1.
Select all objects in the k inematic chain.
2. On the Hierarchy panel, expand the Object
Parameters rollout.
3. Set Precedence to 0.
Note: Default joint precedence occurs whenever
all joints in the kinematic chain have the same
precedence value. Assigning a value of 100 to
all objects in the kinematic chain is exactly the
same as assig ning a value of 0.
Choosing Child-to-Par ent
Pr eced ence (HD Sol ver )
Child–>Parent precedence causes joints closest to
where a force is applied (the end effector) to move
more than joints that are farther away f rom the
force. Like the default precedence, Child->Parent
precedence produces a natural result that is
suitable for many IK solutions.
The difference is that Child
>Parent precedence
assignsuniquevaluestoeachobjectinthe