A method of detecting an occurrence of an event of an event type during an animation, in which the animation comprises, for each of a plurality of object parts of an object, data defining the respective movement of that object part at each of a sequence of time-points for the animation, the method comprising: indicating the event type, wherein the event type specifies: one or more of the object parts; and a sequence of two or more event phases that occur during an event of that event type such that, for each event phase, the respective movements of the one or more specified object parts during that event phase are each constrained according to a constraint type associated with that event phase; and detecting an occurrence of an event of the event type by detecting a section of the animation during which the respective movements defined by the animation for the specified one or more object parts are constrained in accordance with the sequence of two or more event phases.