Yes, that’s the problem. I need to use glReadPixels immediately. In C++ we could call Director::getInstance()->getRenderer()->render(); to force the renderer to proceed pending commands immediately. But in javaScript I can not find way to obtain this renderer nor to call its functions. I develop for native platforms like Android, iOS and win32, not for browsers. I investigate how to use JSB but not succeed yet. I wonder that I can not find a way to obtain a director’s renderer through the Runtime’s calls. Folks what do you think about this approach?