Unknown.

When a car accident leaves Martin Harris in a coma, you'd be forgiven for thinking the biotechnology scientist's week couldn't get much worse. Groggily coming to in an unfamiliar Berlin hospital, Martin finds he has no memory – and worse still, we discover that his wife has no recollection of him whatsoever. He is Unknown – and only he can unlock the secrets of his own identity.

Prime Focus delivered 86 VFX shots over a three month production period for this number one US box office thriller, providing CG snow elements, matte paintings and the climactic hero explosion. The film stars Liam Neeson, Diane Kruger, Aidan Quinn and January Jones.

A huge explosion, which sees a large hotel levelled by the blast, was among the shots completed by the Prime Focus team in London.

"Work began with the arranging and supervision of a bespoke element shoot to capture some footage of ferocious explosions," said Stuart Lashley, VFX Supervisor for Prime Focus.

Special effects experts Artem created two replica sets of the hotel – quarter scale for the exterior and a full 1:1 scale replica set for the interior of the hotel room - which were exploded during a four-camera minature shoot, supervised by SFX Supervisor Steve Begg.

Once these elements had been captured, they were comped together, alongside shots of the real hotel and clips of crowds running away, resulting in the climatic sequence seen on screen. "Only when the explosion was deemed devastating enough did producer Joel Silver give us the final nod of approval," added Stuart.

Set in a wintry Berlin, the snow shots in the film are a combination of on-set snow machines and Prime Focus' CG snow.

"Whilst the practical effects were convincing, we needed to embellish them throughout with CG snow sims," said Shailendra Swarnkar, VFX Supervisor for the Prime Focus team in India. "Our VFX team here in Mumbai contributed the computer generated snow, as well as some beautifully snowy digital matte paintings. The work we completed in Mumbai was sent to Stuart in London for approval before being submitted for client review."

"For Unknown, we needed a company with a skillful, experienced team of artists as well as a solid, proven pipeline that could be relied on to deliver demanding shots in tight timeframes," said Unknown's VFX Producer Tim Field. "Prime Focus was just that. Their VFX work played an instrumental part in making some of the film's key shots happen."