private void makeScene() {
        // load sky
        rootNode.attachChild(SkyFactory.createSky(assetManager, "Textures/Sky/Bright/BrightSky.dds", SkyFactory.EnvMapType.CubeMap));
        //assetManager.registerLocator("http://jmonkeyengine.googlecode.com/files/wildhouse.zip", HttpZipLocator.class);
        Spatial scene = assetManager.loadModel("Models/Test/CornellBox.j3o");
        DirectionalLight sun = new DirectionalLight();
        sun.setDirection(new Vector3f(-0.4790551f, -0.39247334f, -0.7851566f));
        scene.addLight(sun);
        rootNode.attachChild(scene);

    }
This test showcases the possibility to compose the post filtered outputs of several viewports.
The usual use case is when you want to apply some post process to the main viewport and then other post process to the gui viewport
@author Nehon
jme3-examples/src/main/java/jme3test/post/TestPostFiltersCompositing.java