The jAx tool allows creation of a joint coordinate system.

Before starting, select a frame of the animation to be the zero point for joint translations and rotations.

Steps

Creating a joint axis system

1. Select the proximal bone in the joint and click "Insert Selection."
2. Select the distal bone in the joint and click "Insert Selection."
3. Name your axis system. Click Create Axes. If this button does not become available when you type in a joint name, hit enter.
4. Select create Axes without Locators (create axes with locators is more specialized). A set of orthogonal axes will appear in the main Maya window and an object with yourjointname will appear in the Hypergraph.

Aligning the JCS

1. Use Maya object rotation and translation tools to align axes to the expected movement. The z-axis (blue) should be set as the axis with the largest expected rotation, and the y-axis (green) as the second largest expected rotation.
2. The right-hand rule determines the polarity of rotations. Aim thumb along axis arrow direction; fingers curl in positive rotation direction.
3. The z-axis (blue) may have default positiveZ and negativeZ locators and aim and point constraints. The locators can be used to intersect the Z-axis with specific anatomical landmarks. If you do not want to use the locators, then they should be deleted. Go to Hypergraph and select and delete the positiveZ and negativeZ locators. The point constraint and aim constraint objects should automatically be deleted as well.

Setting the axes and viewing 6 DOF graphical data

1. Click SetJointAxes button on the AnatomicalJointAxes window
2. A new object will appear on the far right of the hypergraph named (yourjointname)data.
3. If the graphing window does not appear automatically, go to the Graph Editor.