@Override
    public void setSpatial(Spatial spatial) {
        if (spatial != null && spatial instanceof Node) {
            Node node = (Node) spatial;
            node.attachChild(suspensionNode);
        } else if (spatial == null && this.spatial != null) {
            Node node = (Node) this.spatial;
            node.detachChild(suspensionNode);
        }
        super.setSpatial(spatial);
    }
Alter which spatial is controlled. Invoked when the control is added to
or removed from a spatial. Should be invoked only by a subclass or from
Spatial. Do not invoke directly from user code.

@param spatial the spatial to control (or null)
jme3-jbullet/src/main/java/com/jme3/bullet/debug/BulletVehicleDebugControl.java