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440 Chapter 12: Animation
animation keys. Applied IK works with any
linked hierarchy of objects except for bones
that use the HI Solver or the IK Limb Solver. It
can combine forward kinematics with inverse
kinematicsonthesameobjects. Youcan
apply it automatically to a range of frames, or
interactively to single frames.
Ap plied IK is fast and accurate, but it creates
keys for every object in the k inematic chain,
on every frame. T he large number of keys
can make it difficult to adjust the animation
later. Use Applied IK repeated ly to adjust the
animation.
IK Solvers
Select an object in a hierarchy where you want IK to start.
> Animation menu > IK Solver > Apply an IK solver. >
Click the obje ct in the hierarchy where you want the IK
chain to end.
An IK solver creates an i nverse kinematic solution
to rotate and position links in a chain. It applies
an IK Controller to govern the transforms of the
children in a lin kage. You can apply an IK solver to
any hierarchy of objects. You apply an IK solver to
a hierarchy or part of a hierarchy using commands
on the Animation menu. Select an object in the
hierarchy, choose an IK solver, and then click
another object in the hierarchy to define the end of
the I K chain.
BonessystemwithHIIKsolverapplied
Each type of IK solver has its own behavior and
workflow,aswellasitsownspecializedcontrols
and tools that display in the Hierarchy and Motion
panels. IK solvers are plug-ins, so progr ammers
can expand the software’s capabilities by
customizing or writing their ow n IK solvers.
3dsMaxshipswithfourdifferentIKsolvers.
How Does an I K S olver Work?
AnIKsolvergenerallyoperatesinthisway:an
inverse kinematic chain is defined on part of the
hierarchy, say from the hip to the heel, or the
shoulder to the wrist of a character. At the end of
the IK chain is a gizmo, called the goal. The goal
canberepositionedoranimatedovertimeina
variety of ways, often using linkage, parameter
wiring or constraints (page 2–392).Nomatterhow
the goal is moved, the IK s olver attempts to move
the pivot of the last joint in the chain (also c alled
the end effector) to meet the goal. The IK solver
rotatesthepartsofthechaintostretchoutand