Add IK handles to your skeleton

Use inverse kinematics IK handles to control the movement of different parts of your skeleton without disturbing the rest of the skeleton.

Animation > IK > Add IK handle

is a continuous-action tool in which you add IK handles one at a time to a skeleton. To add single-chain handles, choose Single-chain in the option box for this tool. Then, select the root joint, and finally the end effector joint. The tool is still active after this operation, so you can continue to select other parts of the skeleton to put other IK handles on.

To add IK handles

1 Choose Animation > IK > Add IK handle or click its icon.

2 The system prompts:

Pick a joint as the root of a single-chain (multi-chain or spline) handle.

Pick a root joint to start the handle. (You can drag a pick box around a joint to select it.)

3 The system prompts:

Pick a descendant joint as the end-effector of the single chain (multi-chain or spline) handle.

Pick an end joint.

4 If you created a spline handle and you did not select Create Curve to create a new curve, the system prompts:

Pick a curve node as the target of the spline handle.

Pick the curve.

5 After you create a handle, the system prompts you to create another.

6 To view, change, or turn off the parameters of a handle, open the Information window and select the handle.

7 Limits and joint information about a handle can be edited in the Skeleton Editor. To see handle information, choose Handles from the List Type pop-up menu in the Skeleton Editor (Animation > Editors > Skeletons).

Limitations

If you select Single-Chain solver or Spline-handle solver from the Add IK Handles Options box, the handle is not created if it will overlap any existing handle. However, it is acceptable for a Single-Chain handle to share its root/end-effector with a Multi-Chain handle end-effector/root.
Joints can be the end-effector for a maximum of one handle. This restriction prevents handles from overlapping in the modeling windows, thereby allowing you to pick a particular handle. If you need two handles at the same point in the skeleton, you can add additional joints rooted at the same parent.
Joints with handles are represented in the SBD window by a handle icon.
A handle is always drawn from the joint it controls as the end-effector. If you transform the skeleton chain, the handle snaps to maintain its position at the joint.
If a handle is animated, has an expression, or is constrained, then it will still be drawn at the end-effector joint, but its "goal" position for inverse kinematics purposes is the animated/expressioned/constrained position.
Although handles are not displayed in the SBD window, you can still select them. Handle names appear in the Information Window, Action Window, or any other lister that displays names.
Multi-chain or single-chain handles can be both position goals and orientation goals. A position goal handle puts the end-effector joint at the handle's rotate pivot point position. An orientation goal handle orients the end-effector joint to match the orientation of the handle.

Tips for using the spline handles

You can control the spline handles in the Modeling window in several ways:

If you pick a root handle, either:

Use Transform > Move and the left mouse button to move the chain along the curve.
Choose Transform > Rotate and the left mouse button to roll the chain.

If you pick a master handle, use Transform > Rotate and the left mouse button to twist the chain.

To control the shape of the skeleton

You may want to use spline IK to control the shape of the skeleton, but not its position in space. This is useful if you want one curve to control the shape of a number of similar objects in different locations. To do this:

1 Constrain the root joint of the skeleton to the desired object.

2 Create a spline handle.