public void setViewDirection(Vector3f vec) {
        viewDirection.set(vec);
        updateLocalViewDirection();
    }
Alter the character's view direction. Note this only defines the
orientation in the local X-Z plane.

@param vec a direction vector (not null, unaffected)
jme3-jbullet/src/main/java/com/jme3/bullet/control/BetterCharacterControl.java