8

454 Chapter 12: Animation
With a terminator in the neck, the body of the bird is not
affected.
IK Limb Solver
Animating with the IK Limb Solver
The IK Limb solver is specifically meant for
animating the limbs of human characters; for
example, the hip to the ankle, or the shoulder to the
wrist. Each IK Limb solver affects only two bones
in a chain, but multiple solvers can be applied to
different p arts of the same chain. It is an analyt ica l
solver that is ver y fast and accurate in viewports.
To use the IK Limb solver, a bones system must
have at least three bones in the chain. The goa l is
placed at the pivot point of the bone that is two
bones away from the first selected bone.
The IK Limb solver works not only with bone
hierarchies, but with any linked hierarchy that has
at least three elements, and is set up to model a
human limb. The additional requirements are:
• The first joint is "spherical." That is, it has three
degrees of freedom.
• The second joint is "revolute," a robotics term
that means it is based on a pin and has one
degree of freedom.
The IK Limb s olver uses the same controls as
the HI Solver, so it allows for mixing periods
of forward and inverse kinematics in the same
animation period. It does not use the HD Solver
methods of damping, precedence, and setting joint
limits, instead it has a preferred angle parameter,
swivel plane and IK/FK Enabling.
TheIKLimbsolvercanbeexporteddirectlytoa
game engine.
Procedures
To apply a IK limb solver:
1.
Create a chain that has three bones.
2. Select the root of the chain.
3. From the Animation menu, choose IK Solvers
>IKLimbSolver.
4. In the viewport, move the mouse. You will see a
dotted line attached to the c ursor as you move
the mouse.
5. Click the third bone in the chain, or any bone
after the third bone.
The IK Limb solver displays on the bone chain.
The IK Limb solve r only affects two b ones in
the chain, but you need to select the third bone
toputitontheothertwobones.