@Override
    public void simpleInitApp() {
        stateManager.attach(new EnvironmentCamera(32));

        DirectionalLight light = new DirectionalLight(Vector3f.UNIT_Y.negate(), ColorRGBA.White);
        rootNode.addLight(light);

        assetManager.registerLocator("https://github.com/KhronosGroup/glTF-Sample-Models/raw/master/2.0/RiggedFigure/", UrlLocator.class);

        model = assetManager.loadModel("/glTF-Embedded/RiggedFigure.gltf");
        SkinningControl skinningControl = getSkinningControl(model);
        if (skinningControl == null || !skinningControl.isHardwareSkinningPreferred()) {
            throw new IllegalArgumentException("This test case requires a model with a SkinningControl and with Hardware skinning preferred!");
        }

        viewPort.setBackgroundColor(ColorRGBA.LightGray);
    }
This test case validates a shader compilation fix with a model using a PBR material in combination with a
SkinningControl. When you run this application and don't see a RenderException, the test is successful.
For a detailed explanation consult the GitHub issue: https://github.com/jMonkeyEngine/jmonkeyengine/issues/1340
-rvandoosselaer
jme3-examples/src/main/java/jme3test/light/pbr/TestIssue1340.java