9

464 Chapter 12: Animation
Inter face
Thresholds group
ThesesettingsarethesameasthoseinCustomize
menu > Preferences > In verse Kinematics. They
set the threshold for the changes in position and
rotation between the end effector and t he last link
of the chain.
Positi on—Sp ecifies, in units, the "slop" factor
between the end effector and its ass o ciate object.
This is the allowable distance between the end
effector and its object, given the current IK
solution.
Rotation—Specifies the allowable number of
degrees of rotational error b etween a rotat ional
end effector and its associate object.
Solution group
Iterations—Specifies the maximum number of
iterations allowed to solve the IK solution. The
actual number of iterations used depends on the
difficulty of the problem. This value simply puts
acaponit.
Start Time and End T ime—Species the range of
frames in which IK is solved. If the Start Time is set
to 20 and the End Time is set to 80 in a 100-frame
animation, and then the end effector is animated,
the animation of the chain wil l only be correctly
solved within the Star t and End range.
Initial State group
When you first create a hierarchical chain, the
initial position of the bones or objects is the initial
state. The options here let you display, alter, or lock
the initial state. When both of t he options here
are turned off (the default), tr a nsforming the end
effector is different from transforming the other
joints in the chain. When you select and transform
a joint assigned an end effector, you are actual ly
transforming the end effector , and an IK solution
transforms the joints. This alters the position of
the bones or objects in the viewport, but will not
alter their initial state. On the other hand , w hen
you select and transform any of the joints without
end effectors, you alter their initial state.
Show Initial State—Shuts off the real-time IK
solution. Allobjectsinthechainaremovedto
their initial positions and orientations prior to any
changescausedbyIKcalculations.Thepositions
of the end effectors, however, are not affected.
Turn on Show Initial State to view the initial
state, or adjust the initial state of b ones or objects
using end effectors. This is useful when you set
joint limits using the IK controls in the Hierarchy
panel: the joints jump to their limits wh ile you set
them. When Show Initi al State is off (the default),
you can select and alter the initial state of bones
or objects without end effectors, but when you
select a bone or object with an end effector, the
end effector is transformed, leading to an IK
solution; the initial state of the associate object is
not changed. By selecting this, you can transform
the i nitial state of the asso ciated object.
Lock Initial State—Locks all bones or objects in
the chain from direct transformations. You can,
however, transform the end effector of an y joint