1. A computer readable medium storing a computer program for execution by at least one processing unit, the computer program comprising sets of instructions for: receiving a selection of an animation to apply to two or more graphical objects in a scene over a particular time duration; identifying positional parameters for each of the graphical objects, the positional parameters describing the location of the graphical objects within the scene; based on the selected animation, generating modifications to the positional parameter for each of the graphical objects over the particular time duration, wherein the positional parameter of a first graphical object is modified differently by the selected animation than the positional parameter of a second graphical object is modified by the same selected animation; and storing the modifications as data for the scene.