@Override
    public void setSpatial(Spatial spatial) {
        super.setSpatial(spatial);
        if (spatial instanceof TerrainQuad)
            this.terrain = (TerrainQuad)spatial;
    }
Called internally by com.jme3.util.clone.Cloner.  Do not call directly.
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/NormalRecalcControl.java