9

Inverse Kinematics Preferences 831
Procedure
To prevent transforming unlink ed objects while
workin g i n IK mo d e :
1.
Choose Customize menu > Preferences >
Prefe rence Settings dialog > Inverse Kinematics
tab.
2. On the Inverse Kinematics panel, tur n off the
option labeled Always Transform Children Of
The World.
Single, unlinked objects are hierarchies of one
object.Anunlinkedobjectisitsownrootand
also a child of the world, so turning off Always
Transform Children Of The World prevents you
from transforming single objects in IK mode.
Inter face
Applied IK/Interactive IK g roup
Thethresholdanditerationssettingsareatrade-off
between accuracy and speed. With the two groups
of settings you can individually tune the behavior
of Interactive IK and Applied IK. In teractive IK
provides fast, real-time response, so you should
set Interactive IK preferences for speed. Applied
IK provides the IK solution (page 3–955) to match
the follow objects (page 3–943) very closely. You
should set applied IK preferences for accuracy.
Positi on—Sets how close the end effector has to
get to the follow object or cursor position for the
object to be considered a valid solution. The value
represents a distance in the current display unit
system. Small values increase accurac y but ta ke
longer to solve.
Rotation—Sets how accurately the end effector has
to match the orientation of the follow object to be
considered a valid solution. The va lue represents
a rotation angle in degrees. Small va lues increase
accuracy but take longer to solve.
Iterations—Sets the maximum number of times
3dsMaxrepeatstheIKcalculationstofinda
valid solution. A high iterations value increases
the chance that 3 ds Max c an calculate a valid
IK solution, but the calculation takes longer to
complete.
Ungrouped controls
Use S econda ry T hr esh old—Compares the second
derivative of the end effector (page 3–933) to a very
small threshold. If the derivative is within the
threshold, IK is terminated.
Always Transform Children Of The World—Applies
when IK is turned on in both move and rotate
mode. It affects only an object that’s a direct child
of the world when the object is selected.
For example, if the root of an IK chain is a child
of the world, and you’re manipulating an object
at the end of the chain (the root object itself isn’t
selected), any constraints set for the root object
w i ll be observed. However, if you select the root
object and t ry to move it, its constraints will be
ignored.