A method of rendering image frames for a videogame includes the steps of, for one or more predetermined features of a virtual environment of a videogame, setting a respective per-frame movement distance threshold; calculating a respective minimum frame rate at which movement of the or each predetermined features of the virtual environment of the videogame between successive image frames remains within the respective movement distance threshold; detecting whether the current frame rate is below one or more of the respective minimum frame rates; and if so, reducing a rendering resolution used during rendering of one or more subsequent image frames to increase the frame rate above one or more of the minimum frame rates.