When you drop an object into a Character Extension, the object’s Translation and Rotation values are added as reference properties in the Character Extension properties. A Label property is also added for any object added to an Extension, which lets you create a second non-unique name for the object.

The Labels that you define for each object in an Extension have a similar function to the body part names in the character Mapping List - they both let you describe a structure. The difference is, you can change the Label names for objects that make up your Character Extension.

For example, on a character with Character Extensions for two wings, you might want to mirror poses from the right wing to the left. To do this, you can create a symmetrical set up where the two Character Extensions are each made up of three objects. All of the wing objects must have a unique name in the scene, but you can indicate to MotionBuilder which objects correspond wing-to-wing by giving each pair the same Label, such as “WingA,” “WingB,” and “WingC.” Using the same Label for two objects indicates to MotionBuilder that the objects are compatible, so you can retarget animation between them, and mirror poses on them.