Now it is time to take your film to the next level, visually speaking at least. Presumably, at this stage your animation is the best it can ever be. (If not, go back and make it so!) You will have hopefully worked at it and modified it through constant testing and changes, so now it will be as close to perfect as it ever can be. Having gone through that painstaking, extended process, you will want the visual quality of your film to completely support its animated movement. That is where clean-up comes in.