To promote The Hobbit: Desolution of Smaug Microsoft and Warner Bros are offering a free 3D printer blueprint of The Key of Erebor from the film.

The advertising campaign will run across MSN, Xbox 360 and Windows 8 with an interactive dive into the film including information about characters, events, artefacts, actor biographies, behind the scenes videos and desktop wallpapers. But the best part is the free 3D printer blueprint.

The download will become available on 13 Secember - the day of the film’s release. Fans will be able to download the blueprint from the ad then connect to any 3D printer to make it.

The ad campaign itself is aiming to draw people in to the Hobbit movie website. But with very few people  who own a 3D printer it’s probably more of a proof of concept rather than a tool for attracting users.

Danni Murray, director of media and marketing partnerships, Warner Bros UK & Ireland says: “We’re incredibly excited about this integrated partnership opportunity. We asked Microsoft to come up with a solution that challenged the previous conventions around what was possible with its display offering and we’re confident this interactive campaign will excite and engage fans as they journey into the second film in the trilogy.”