Render the motion vector of objects to another render texture. (ie calculate the velocity of each object and render that as a color) Use that to define the amp

Render the motion vector of objects to another render texture. (ie calculate the velocity of each object and render that as a color) Use that to define the amplitude and direction of your blur effect in a post pass. And you might want it to be the motion relevant to the camera. For Mario, probably not, but for an FPS you want to edges of the screen to blur as the camera moves forward.