@Override
    public void simpleUpdate(float tpf){
        fbNode.updateLogicalState(tpf);
        fbNode.updateGeometricState();
    }
Demonstrates FrameBuffer usage.
The scene is first rendered to an FB with a texture attached,
the texture is then rendered onto the screen in ortho mode.

@author Kirill
jme3-examples/src/main/java/jme3test/post/TestFBOPassthrough.java