@Override
    public void write(JmeExporter e) throws IOException {
        OutputCapsule cap = e.getCapsule(this);
        cap.write(x, "x", 0);
        cap.write(y, "y", 0);
        cap.write(z, "z", 0);
        cap.write(w, "w", 1);
    }
Serializes to the specified exporter, for example when saving to a J3O
file. The current instance is unaffected.

@param e the exporter to use (not null)
@throws IOException from the exporter
jme3-core/src/main/java/com/jme3/math/Quaternion.java