protected ViewPort createOffViewPort(final String name, final Camera offCamera) {
        final ViewPort offView = new ViewPort(name, offCamera);
        offView.setClearFlags(true, true, true);
        offView.setBackgroundColor(backGroundColor);
        return offView;
    }
creates an off-screen VP

@param name the desired name for the offscreen viewport
@param offCamera the Camera to be used (alias created)
@return a new instance
jme3-core/src/main/java/com/jme3/environment/EnvironmentCamera.java