private void setUpLight() {
        // We add light so we see the scene
        AmbientLight al = new AmbientLight();
        al.setColor(ColorRGBA.White.mult(0.1f));
        rootNode.addLight(al);

        DirectionalLight dl = new DirectionalLight();
        dl.setColor(ColorRGBA.White);
        dl.setDirection(new Vector3f(2.8f, -2.8f, -2.8f).normalizeLocal());
        rootNode.addLight(dl);
    }