@Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule oc = ex.getCapsule(this);
        oc.write(rootStruct.getName(), "rootClass", null);
    }
Update data and layout (when needed) using a Struct class.

@param struct
jme3-core/src/main/java/com/jme3/util/struct/StructStd140BufferObject.java