Actor Brad Pitt films a scene from “World War Z” in Glasgow City centre on August 18, 2011 in Glasgow, Scotland. The film, which is set in Philadelphia, will be shot in various parts of the city transforming it into ruins to shoot a post apocalyptic zombie film. (Photo by Jeff J Mitchell/Getty Images)

An actor appears as an American police officer as filming for the Brad Pitt film “World War Z” continues in Glasgow City centre on August 17, 2011 in Glasgow, Scotland. (Photo by Jeff J Mitchell/Getty Images)

A man works on the set as filming for the Brad Pitt film “World War Z” continues in Glasgow City centre on August 18, 2011 in Glasgow, Scotland. (Photo by Jeff J Mitchell/Getty Images)

Filming for the Brad Pitt film “World War Z” continues in Glasgow City centre on August 18, 2011 in Glasgow, Scotland. (Photo by Jeff J Mitchell/Getty Images)