The typical Ogre application will render one frame after another, ceaselessly.That means we just start the Root::startRendering() method and everything will be done automatically.
However, sometimes we want to update the scene after we change some scene content. With Root::startRendering(), we can just do our redraw process and let the system to render the new scene.
Moreover, Root::startRendering() method simply starts a small loop that calls another method renderOneFrame().
Thus, we can manually do rendering with renderOneFrame() method.