@Override
    protected void setParent(Node parent) {
        super.setParent(parent);

        // If the geometry is managed by group node we need to unassociate.
        if (parent == null && isGrouped()) {
            unassociateFromGroupNode();
        }
    }
Removes the {@link GeometryGroupNode} association from this
<code>Geometry</code>.

Should only be called by the parent {@link GeometryGroupNode}.
jme3-core/src/main/java/com/jme3/scene/Geometry.java