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444 Chapter 12: Animation
Binding an Object to the World
You can bind an object to the world if you want the
object to hold its position and orientation as long
as possible during IK operations.
If you are animating a walking figure you wa nt
one foot to remain in place while you position the
other foot. Without binding, the whole hier archy
would have a tendency to slide around when you
attempt to position a foot. Binding both feet to
the world ensures that the unselected foot stays in
place while you position the other foot.
B inding a n Object to a Follow Object
You can bind a selected object in your hierarchy
to any other object that is not a descendant of the
selected object. T his other object is called the
follow object.
The behavior of the bound object varies depending
on the state of the Relative buttons next to the bind
options.
• WhenRelativeisinactive,theboundobject
tries to match the exact position and orientation
of its pivot point to the position and orientation
of the follow object’s pivot point.
• When Relative is active, the bound object
mimics any changes in position or rotation of
thefollowobjectbutdoesnottrytomatchit
exactly.
You might want to animate a figure that always
points to another object. Bind the hand of the
figure to the other object with Relative active. Turn
IK on, and as you move the object, the hand and
armofthefiguremovetopointatit.
Unbinding Objects
Ifyoudecidethatyoudonotwantanobjecttobe
bound you can either turn off the Bind O rientation
and Bind Position boxes, or unbind the object
from its follow object.
• If you turn off the binding options, you disable
theeffectofbindingwithoutremovingthe
binding to a follow object. This method is
handy if you decide to reposition a follow object
after you have bound an object to it.
• If you unbind an object, it permanently
removes the binding to a follow object.
Controlling IK Precision (HD
Solver)
Even with carefully defined joint precedence and
joint parameters there are many valid IK s olutions
for any placement of an end effector. You set
position and rotation thresholds to control IK
precision and solution speed.
• The threshold and iteration settings are found
on the Motion panel on the IK Controller
Parameters Rollout, when the end effector is
selected.
• The threshold and iteration settings for the HD
solver are also found on the Inverse Kinematics
tab of the Customize > Preferences dialog.
Position Threshold—Sets how close the end effector
has to get to the follow object or cursor position to
be considered a va lid solution. The value expresses
a distance in the current unit system. Small values
increase accuracy but take longer to solve.
Rotation Threshold—Sets how accurately the end
effector has to match the orientation of the follow
object to be considered a valid solution. The value
expresses a rotation ang le in deg rees. Small values
increase accuracy but take longer to solve.
Iterations—Sets the maximum number of times
3dsMaxrepeatstheIKcalculationstofinda
valid solution. A high Iterations value increases
thechancethatthesoftwarecancalculateavalid
solution, but takes longer to complete. The
following rules apply: