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472 Chapter 12: Animation
Terminator option in the Object Parameters rollout
YouusetheTerminatoroptionintheObject
Parameters rollout to stop calculation of the
kinematic chain before it reaches the root object
of the hierarch y. A terminator object stops
calculation at the terminator’s child object; the
terminator itself is not affected by the IK solution.
This gives you very precise control over the
behavior of the kinematic chain.
For example, look at the bird in the fig ure. The bird
islinkedwithitsbodyastherootofthehierarchy.
If you use inverse kinematics to move t he duck, all
objects from the duck to the body will be affected
by the IK sol ution. However, if you define a neck
bone as a terminator object, then only the objects
fromtheducktotheneckvertebraeareaffected.
With a terminator in the neck, the body of the bird is not
affected.
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 parts of the same chain. It is an analytical
solver that is very fast and accurate in viewports.
To use the IK Limb s olver, a b ones system must
have at least three bones in the chain. The goal is
placed at the pivot point of t he bone that is two
bones away from the first selected bone.