9
IK Solvers 441
reposition the end effector to coincide w ith the
goal.
UsinganIKsolvertoanimateanarm
Frequently, the end effector is constrained to the
ground plane. For example, you might "pin" the
toes as the heels lift in a character walk cycle. Then
the movement of the root of the chain poses the
legs up from the toes.
Four plug-in IK solvers ship with 3ds Max:
• HI (History-Independent) Solver (page 2–446)
The HI S olver is the preferred metho d for
character animation, and for any IK animation
in long sequences. With HI Solvers, you can set
up multiple chains in a hierarchy. For example,
a character’s leg might have one chain from h ip
to ankle, and another from heel to toe.
Becausethissolver’salgorithmis
history-independent, it is fast to use
regardless of how many frames of animation are
involved. Its speed is the same on frame 2000
as it is on frame 10. It is stable and jitter-free in
viewports. This solver creates a goal and an end
effector (although the d isplay of end effector
is off by default). It uses a swivel angle (page
2–449) to adjust the solver plane to position the
elbow or the knee. You can display the swivel
angle manipulator as a handle in the viewport,
and adjust it. HI IK also uses a prefe rred angle
to define a direct ion for rotation, so the elbow
or knees bend correctly.
• HD (History-Dep endent) Solver (page 2–461)
TheHDSolverisasolverwell-suitedtouse
for animating machines, especially ones with
sliding parts that require IK animation. It lets
you set up joint limits and precedence. It has
performanceproblemsonlongsequences,so
ideally use it on short animation sequences. It
is goo d for animating machines, especially ones
with sliding parts.
Because this solver’s a lgorithm is histor y
dependent, it works best for short animation
sequences. The later in the sequence it is
solving,thelongerittakestocalculatea
solution. It allows you to bind the end effector
to a follow object, and it uses a system of
precedence and damping to define the joint
parameters. It allows for sliding joint limits
combined with IK animation, unlike the HI IK
solver, which only allows for sliding joint limits
when using FK movement.
• IK Limb Solver (page 2–472)
The IK Limb solver operates on only two bones
inachain.Itisananalyticalsolverthatisfastin
viewports, and can animate the arms and legs
of a character.
TheIKLimbsolvercanbeusedforexportto
game engines.
Because this solver’s algorithm is
history-independent, it is fast to use
regardless of how many frames of animation
areinvolved. Itsspeedisthesameonframe
2000 as it is on frame 10. It is stable and
jitter-free i n viewports. This solver c reates a
goal and an end effector (although the display
of end effector is off by default). It uses a swivel
angle (page 2–449) to adjust the solver plane to
position the elbow or the k nee. You can target
the swivel angle to an another object to animate
it. IK Limb Solver also uses a preferred angle