@Override
    protected void initFilter(AssetManager manager, RenderManager renderManager, ViewPort vp, int w, int h) {
        material = new Material(manager, "Common/MatDefs/Post/Fade.j3md");
    }
Creates a FadeFilter with the given duration

@param duration the desired duration (in seconds, default=1)
jme3-effects/src/main/java/com/jme3/post/filters/FadeFilter.java