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456 Chapter 12: Animation

A helper object is automat ically placed at each

vertex when Spline IK is assigned. Each vertex is

linked to its corresponding helper, so a vertex can

be moved by moving the helper.

UnliketheHISolver,theSplineIKsystemdoes

not use a goal. The positions of helpers/vertices

in 3D space is the only factor that determines the

shape of the linked str ucture.

Note: MovingtheSplineIKhelperstocurlthe

spline can sometimes cause b ones to rotate or

flip unexpectedly. If this happens, you can try

choosing a different upnode object with the IK

chain’s Pick Upnode option in the IK Solver

Properties rollout (see

Spline IK Solver Rollouts

(page 2–461)

), or use a different IK method for

your hierarchy.

Apply ing a Spli ne I K Solv er

TheSplineIKsolvercanbeappliedatthetime

bones are created, or after the bone structure has

already been made.

To apply a spline IK solver when bones are created:

Choose Create panel > Systems > Bones.

2. In the IK Chain Assignment rollout, choose

SplineIKSolver, and check Assign to Children

and Assign to Root.

3. Drawthebonestructureasusual.Whenyou

right-click to end the bone creation process, the

Spline IK Solver dialog (page 2–459)

appears.

Set parameters and click OK.