8

420 Chapter 12: Animation
Bound Objects—
Objects in your hierarchy can be
bound to the world, or they can be bound to other
objects called
follow objects (page 3–1037) .
Bindingallowsobjectsinyourhierarchytobe
influencedbyobjectsthatarenotpartofthe
hierarchy.
• An object bound to the world will attempt to
maintain its current po sition and orientation.
• An object bound to a follow object will attempt
to match the position and orientation of the
follow object.
•Youcanbindtoafollowobjectwhenyouuse
an HD Solver, or when Applied IK is used.
Ifyouwanttobindtoafollowobjectwhen
usinganHIorIKLimbSolver,applyaposition
constraint between the goal and any follow
object of your choice (usually a point, d ummy,
spline, or bone).
Enabled IK —(HI Solver) When using the HI Solver,
you can animate with either inverse kinematics
orforwardkinematics(FK).WhenEnabledis
turned on, inverse kinematics controls the chain,
and keyframes are placed only on the goal. When
Enabledisturnedoff,forwardkinematicrotational
keysareplacedonallthebones.
IK /FK Snap—(HI Solver) When using the HI Solver,
if y ou animate using both IK and FK, you might
create a situation where the goal has moved away
from the end of the chain, causing a jump in the
animation. Pressing IK/FK Snap will result in
the goal b eing moved back to match the position
of the end effector, eliminating the jump in the
animation.
IK for FK pose—(HI Solver) When this button is
turned on, moving the goal automatically sets
rotation k eys for the bones. In effect, this lets you
use IK m anipulation to create your pose, sett ing
FK keys.
IK M ethods
Inversekinematicsbuildsontheconceptsof
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 2–408)
and Inverse Kinematics (IK) (page 2–417) .
IK Solvers
IK solvers (page 2–421) are specialized controllers
that apply IK solutions procedurally across a range
of frames.
Four different IK solvers ship with 3ds Max:
• HD (Histor y-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.
•Workonanyhierarchyorbonestructure.
• Calculate IK solutions for all frames in real-time
as you make changes.
• AllowyoutocreatemultipleoroverlappingIK
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 key f r ames only on the IK goal
orendeffector,asopposedtoforwardkinematics
(or the non-solver IK methods), which place