possible to move ArmControl

Limiting the range of motion of an IK system

It's possible to move ArmControl so that the mechanical arm fully extends to a straight position or orients
itself to other positions that you don't necessarily want.

You can limit the range of motion of the arm to ensure that the IK system poses in a predictable manner.
In the following section, you limit the motion for the IK system as follows:

1.  Lock the translation of the control object (ArmControl) so that it can only move in Y and Z. By
   locking the X channel so it cannot be selected or modified, the arm will not be able to move from
   side to side.
2. Lock the rotations on the swiveling base for the arm so it only rotates about its Y axis, and not
   about its X or Z axes.
3.  Limit the translations for the Arm Control so the mechanical arm cannot fully extend to a
   straightened position.

To lock the Translate X channel for ArmControl
1. In the Hypergraph, select the ArmControl node.
2. Open the Channel Box to view the transform channels for ArmControl.
3. Set all Translate or Rotate channels to 0, if they are not already.
4. In the Channel Box, select the Translate X channel by clicking on its name.
5. Right click on the word Translate X.
A drop-down menu appears.
6. From the drop-down menu, choose Lock Selected.

The numerical field for Translate X is dimmed indicating that the channel is locked. If you try to
move ArmControl in X, it will not be possible unless you unlock the Translate X channel.

To lock the Rotate X and Z channels for SwivelBase
1. In the Hypergraph, select only the SwivelBase node.
2. Open the Channel Box to view the rotation channels for SwivelBase.
3. Set all Translate or Rotate channels to 0, if they are not already.
4. In the Channel Box, select the Rotate X and Rotate Z channels by control-clicking on their
names.

5. Right click on either of the selected names.
A drop-down menu appears.
6. From the drop-down menu, select Lock Selected.

To confirm that the Rotate X & Z channels are locked

1. In the Hypergraph, ensure only the SwivelBase node is selected.
2. In the view, select Panels > Orthographic > top.
3. In the view, select Shading > Smooth Shade All.
4. Dolly the top view so you can fully view the mechanical arm as shown below.
5. Using the ChannelBox, rotate SwivelBase by typing 45 in the Rotate Y channel and pressing Enter.

SwivelBase rotates in the view but the mechanical arm does not rotate. You first might think
something is wrong because SwivelBase and all of the arm's skeletons and surfaces are parented
into the same hierarchy.

NoteYou may sometimes discover that something doesn't work in the manner you originally anticipated
when setting up an IK system. When this occurs, it's useful to stop and diagnose why something is
working the way it is (or not working the way it should). In that way you can retrace your actions to
determine where the problem resides.

ArmControl and IK Handle are not parented into the SwivelBase hierarchy. Because ArmControl and IK
Handle control the movements of the mechanical arm, they must be parented into the SwivelBase
hierarchy in order for the arm to rotate when SwivelBase is rotated.

To parent the IK Handle into the skeleton hierarchy

1. In the Hypergraph, select the SwivelBase node.
2. In the ChannelBox, reset the Rotate Y channel for SwivelBase to 0.
Setting any previous transformations to zero is necessary before parenting the IK Handle beneath
SwivelBase in the hierarchy.
3. Unselect the SwivelBase node before performing the following steps.
4. In the Hypergraph menu, select View > Frame All.
The Hypergraph displays all the nodes for the scene.
5. In the Hypergraph, shift-select the nodes named ikHandle1, ArmControl, and SwivelBase.
The order of selection is important. You want to shift-select the items that will be the child nodes
first, and then shift-select the item that will be the parent node last.
6. In the main menu, select Edit > Parent (Hotkey p).
In the Hypergraph, IKHandle and ArmControl are now child nodes for the SwivelBase node in the
skeleton hierarchy.