if (pn_rc->actuator)
    {
      // set the viewport to a texture size
      glViewport(0, 0, 128, 128);

      // run actuators
      exec_actuator (pn_rc->actuator);

      // reset the viewport to window size and draw
      glViewport(0, 0, pn_image_data->width, pn_image_data->height);
      SDL_GL_SwapBuffers();
    }