public void setMask(AnimationMask mask) {
        this.mask = mask;
    }
Meant for internal use only.

<p> 
Note: This method can be invoked from the user code only if this Action is wrapped by a {@link BaseAction} and
the {@link BaseAction#isMaskPropagationEnabled()} is false.
</p>

@param mask an animation mask to be applied to this action.
@see com.jme3.anim.AnimLayer to adjust the animation mask to control which part will be animated
jme3-core/src/main/java/com/jme3/anim/tween/action/Action.java