2009

TIP Choose one of the Mirror Paste options if you want to mirror the joint
parameter settings as you paste them. This is very useful when pasting from one
side of an object to another, such as left arm joints to a right arm.
You can also copy joint settings from a non-IK controller to an IK controller,
but you can't copy from an IK controller to a non-IK controller.
Activating Joint Axes
You set whether an object can move or rotate about a given axis by using the
Active check box in the joint rollouts. Joints have a maximum of six possible
axes: three for rotation and three for position. You constrain the motion of a
joint by setting which axes are active.
■ A joint with all axes active can move and rotate freely, independent of its
parent.
■ A joint with all axes inactive is locked to its parent and cannot move
independently.
■ The setting of IK joint axes overrides Inherit and Lock settings on the Link
Info rollout.
Understanding Joint Axis Orientation
IK joint axes for an object are defined by the Local axes of the object’s parent.
That means if you activate the X axis of an object’s rotational joint parameters,
the object rotates about its parent’s X axis, not its own X axis.
You might have a problem when you set joint parameters for an object whose
local coordinate system is oriented 90 degrees from its parent’s coordinate
system. In such a case, the rotation angle about one axis becomes
indeterminate. The result is that one axis will often cause rotation about one
of the other two axes.
The following techniques will make setting joint parameters easier and more
successful:
■ Assemble IK hierarchies with objects aligned along the World axes.
■ Consider using the Adjust Pivot on page 3476 functions to align your object
pivots with either the World axes or the root object of the hierarchy.
3470 | Chapter 15 Animation