9

Inverse Kinematics Methods 439
IK for FK pose—
(HI S olver) When this button is
turned on, moving the goal automatically sets
rotation keys for the bones. In effect, this lets you
use IK manipulation to create your p ose, setting
FK keys.
IK Methods
Inverse kinematics builds on the concepts of
hierarchical linking. To understand how IK
works, you must first understand the principles of
hierarchical linking and forward kinematics. See
Animating with Forward Kinematics (page 2–426)
and Inverse Kinematics (IK) (page 2–435).
IK Solvers
IK solvers (page 2–440) are specialized cont rollers
that apply IK solutions procedurally across a range
of frames.
Four different IK solvers ship with 3ds Max:
• HD (History-Dependent) Solver
• HI (History-Independent) Solver
•IKLimbSolver
•SplineIKSolver
Tip: In order to put an IK solver on a two-bone
chain, a third bone is needed. Choose the first
bone, then from the Create menu click IK solver,
then click the third bone in the viewport.
In general, all IK solvers:
•Workonanyhierarchy.
• Work on any hierarch y or bone structure.
• Calculate IK solutions for all frames in real-time
as you m a ke changes.
• Allow you to create multiple or overlapping IK
chains within a single hierarchy.
• Display active joint axes and joint limits
graphically.
• Use a node, goal or an end effector to animate
the end of a chain.
An IK solver places keyframes only on the IK goal
orendeffector,asopposedtoforwardkinematics
(or the non-solver IK methods), w h ich place
rotationkeyframesonthebonesorhierarchical
objects themselves.
Ot her IK Met hods
In addition to the IK solvers, 3ds Max provides
two non–solver methods of inverse kinematic
animation: Interactive IK and Applied IK. These
IKmethodsdonotapplyanIKsolver.
Note: These are older IK methods carried over
from the earliest versions of the software. It is
generally recommended that IK Solvers be used in
most c ases rather than Interact ive or Applied IK.
• Interactive IK (page 2–480)
Interactive IK gives you the ability to use IK
manipulation on hierarchies without applying
an IK solver. You animate your IK structure
by activating Interactive IK (found in the
IK panel of t he Hierarchy panel and on the
Hierarchy toolbar) and manually animating
the position of end effectors. IK solutions
are calcu lated only for the keyf rames you set.
All other motion is interpolated as set by the
object’s controllers. Moving the end of the
chain simply adds rotational keys to the objects
in the chain. The objects can have joint limits
assigned, for additional control. The chain can
also be terminated using the tools in the Auto
Termination rollout (page 2–499).
• Applied IK (page 2–481)
With Applied IK, you animate follow objects
and the program calculates the solution on
every frame of a specified r ange. The IK
solution is applied as standard transform