8

446 Chapter 12: Animation
difficulty of the pr oblem. This value simply puts
acaponit.
Start Time and End Time—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-f r ame
animation, and then the end effector is animated,
the animation of the chain will only be correctly
solved within the Start 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 the options here
are t urne d off (the default), transform ing 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 actua l 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, when
you select and transform any of the joints without
end effectors, you alter their initial state.
Show Initial S tate—Shuts off the real-time IK
solution. Allobjectsinthechainaremovedto
their initial positions and orientations prior to any
changes caused by IK calculations. The positions
of the end effectors, however, are not affected.
Turn on Show Initial State to view the initial
state, or adjust the init ial st ate of bones or objects
using end effectors. This is useful when you set
joint limits using the IK controls in the Hierarchy
panel: the j oints jump to their limits w hile you set
them. When Show Initial 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 effec tor is tr ansformed, leading to an IK
solution; the initial state of the associate object is
not changed. By selecting this, you can transform
the initial state of the associated object.
Lock Initial State—Locks all bones or objects in
the chain from direct transformations. You can,
however, transform the end effector of any joint
to generate the IK solution without altering the
initial state. Activate this when you want to avoid
accidentally selecting and transforming joints that
are not assigned end effectors. When Show Initial
State is selected, Lock Initial State is i gnored.
Update group
The options in this group determine how the IK
calculation is solved during the transformation of
the end effector.
Precise—Solvestheentirechainpreciselyforall
frames from the Start time to the current time.
When you release the mouse button, the chain will
not move. Since all frames must be solved from
Start to current time, the solution takes longer if
the current frame is 1000 rather than 100.
Fast—Solves the chain only for the current frame
whilethemouseismoved.Releasingthemouse
button solves for all frames. Although this is
faster than Precise, sometimes the cur rent-frame
solution differs slightly from the a ll-frame
solution. As a result, when you release the mouse,
the objects in the chain mig ht shift a bit.