Filming Oscar-nominated Room was 'pretty intense,' says Ottawa-based assistant director

In the Oscar-nominatedRoom, actors Brie Larson and Jacob Tremblayspend the first third of the film confined in a tiny, claustrophobicspace.

According to Reid Dunlop, it'sno illusion: the opening chapters in the taleof a mother and her young son held captiveby a sexual predator really were filmed in a 150-square-foot seterectedon a production studio in Toronto.

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"It was a very small box that was builtwith removable panels so a camera could go anywhere," said Dunlop, the film'sfirst assistant director, on CBC Ottawa'sAll In A DayThursday.

"They wanted to make it as real as possible, address [the characters' confinement]as realistically as possible, and give the actors a real sense of the claustrophobia."

Inspired by the novel by London, Ont.,-based Irish-Canadian author EmmaDonoghue,Roomwas nominated Thursday for Oscarsfor best picture, best director and best adapted screenplay.

Larson was also nominated in the best actress category, as the young woman who endures repeated sexual assaults by her and her son's captor before escaping midway through the film.

From a technical standpoint, making the film shouldhave been simple,said Dunlop,whose credits include Canadian television series such asSlings and Arrows,Michael: Tuesdays and Thursdays, andKids in the Hall: Death Comes to Town.

But the enclosed filming space combined with the harrowing subject matter meant the process was anything but easy, said the Chelsea, Que., assistant director.

"It's two people in a room, how hard can that be?But itbecame very psychologically difficult for a lot of the crew, for a number of reasons," said Dunlop.

"We shot 15, maybe 23 days in that box. So it was pretty intense."

Dunlop told All In A Day host Alan Neal he knewRoomwas going to do well after he saw the finished version and that belief was reinforced after the film took home the coveted people's choice award at the Toronto International Film Festival.

He praised director Lenny Abrahamson's ability to take Donoghue'snovel told from five-year-old Jack'sperspective and bring it to the screen, while also lamenting that Tremblay wasn't nominated for best actor.

Dunlop also saidhe was still wrapping his head around the fact that a film he'd worked on was up for multiple Oscars.

"It's a weird feeling, for sure," he said. "It's a first time, and it's sort of trippy."