@Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule oc = ex.getCapsule(this);
        oc.write(enabled, "enabled", true);
        if (value == null) {
            oc.write(true, "isNull", false);
        }
    }
Enable or disable this <code>MatParamOverride</code>.

When disabled, the override will continue to propagate through the scene
graph like before, but it will have no effect on materials. Overrides are
enabled by default.

@param enabled Whether to enable or disable this override.
jme3-core/src/main/java/com/jme3/material/MatParamOverride.java