Right now, if I have a character that walks from one end of the screen to another, I have to render the whole screen. It would be great if there was a way to set a render region that would track the character across the screen, maybe by setting key frames on the render region itself. A keyframe would be set at the beginning of the render, and more keyframes that follow the character so that only the portion of the character is rendered throughout the render process. And if that key frame placement could be made automatically it would be tremendous. It would dramatically cut down on render times without needing more powerful computers to render.