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476 Chapter 12: Animation
Thebonestructurejumpstothesplineand
takes its shape, and a helper is created on
the spline at each vertex. A Path constraint
is automatically assigned to the root bone to
constrain it to the helper/vertex at that e nd of
the spline.
To specify a spline af ter the spline IK solver is applied:
You can also apply a Spline IK solver to an existing
bone structure w ithout selec ting a spline, then
choose the spline later.
1. Create a bone st r ucture without an IK chain.
2. Selecttheboneorobjectwhereyouwanttothe
solver to start.
3. Choose Animation menu > IK Solvers > Spline
IK Solver. In the viewport, move the cursor to
theboneorobjectwhereyouwantthechainto
end and click that bone. Then right-click in the
viewport to end t he IK solver creation without
choosing a spline.
4. CreateasplineorNURBScurvetobeusedwith
theSplineIKsystem. Itisrecommendedthat
you apply the Spline IK Control modifier (page
1–830) to it and then click Create Helpers to
place helpers at each vertex, m aking the spline
easier to control.
5. Select the IK chain cross hairs and access the
Motionpanel.OntheSplineIKSolverrollout,
click Pick Shape and click the spline.
With this method, the position constraint is not
automatically assigned to the root bone, so it
must be assigned manually.
6. Select the root bone. Choose Animation menu
> Constraints > Path Constraint, and then click
the spline.
This moves the bone structure to t he spline,
if they’re apar t, and creates a Position List
controller for the bone with the Path C onstraint
as the second (active) constraint.
Note: This also animates the bones along the
path.Ifyoudon’twantthis,deletethesecond
animation key.
Work ing with the Spline IK Solver
To use the Spline IK Solver, move the helpers to
shape the spline. Do not move the spline. The
shape of the spline is determined by the positions
ofthevertices,somovingthesplineitselfhasno
effect on the bone structure. If the spline is mo ved,
it will snap back to the helpers the next time a
helper is moved. However, it is recommended that
younotmovethesplineatall.
OnceyouhavefinishedsettingupthesplineIK
solver, it can be helpful to freeze the spline to avoid
accidentally moving it.
Moving helpers changes the shape of the spline. To
twistthespline,selectthesplineIKchainobject
andgototheMotionpaneltochangetwistangles
in the IK Solver Properties rollout.