@Override
    public void read(JmeImporter importer) throws IOException {
        super.read(importer);
        InputCapsule capsule = importer.getCapsule(this);
        orient = (Matrix3f) capsule.readSavable("orient", null);
        look = (Vector3f) capsule.readSavable("look", null);
        left = (Vector3f) capsule.readSavable("left", null);
        alignment = capsule.readEnum("alignment", Alignment.class, Alignment.Screen);
    }
Sets the type of rotation this Billboard will have. The alignment can
be Camera, Screen, AxialY, or AxialZ. Invalid alignments will
assume no billboard rotation.

@param alignment the desired alignment (Camera/Screen/AxialY/AxialZ)
jme3-core/src/main/java/com/jme3/scene/control/BillboardControl.java