code: protected void paintScene () {
      viewSurf.saveTx();
      viewSurf.begin();
      viewSurf.clear(cred, cgreen, cblue, calpha);
      try {
        rootLayer.paint(viewSurf);
      } finally {
        viewSurf.end();
        viewSurf.restoreTx();
      }
    }
docs: Renders the main scene graph into the OpenGL frame buffer.