The movie 2012 might be described as apocalypse porn, with its lurid, graphic depictions of population-pulverizing earthquakes, volcanoes and floods.

By contrast, the upcoming film The Road, an adaptation of a novel by Cormac McCarthy (No Country for Old Men), is not about the devastation but the sickly afterglow.

Viggo Mortensen stars as a devoted father who escorts his young son through a blasted landscape touched by a maddeningly non-specific event that has left the country desolate, burned-out and all but lifeless.

Survivors are not worried about evading computer-generated tsunamis or lava. Mostly, they search for food while avoiding other more brutish survivors.

Ambiguity rules this universe to the extent that even the characters are listed in the credits as Man (Mortensen) and Boy (13-year-old Australian actor Kodi Smit-McPhee).

Man and Boy reunited at the Toronto International Film Festival in September, where a paternal Mortensen participated in interviews paired with Smit-McPhee, dutifully making sure the younger actor was included in the press process.

For his part, Mortensen says he didn't sweat the mystery surrounding the end of the world, pointing out that such an event would be equally mysterious for the people caught in the middle of a cataclysm.

"I thought that if civilization went out, so did the Internet and so did communication," Mortensen says. "So some of it is rumour, some of it is fact."

Mortensen says his preparation demanded that he fill out some of his own backstory for himself.

"I knew what my name was and where I was raised in the United States, but it's not something we talked about and, in a sense, it's not the most important thing," Mortensen says.

"The way the world looks and the state of the planet serves to focus our attention on each other," he says, referring to the intense relationship between his character and his screen son.

The Road was largely shot in some of the more ravaged landscapes of Pennsylvania as well as real disaster areas, including a post-Katrina New Orleans and near the post-volcanic Mount St. Helens in Washington.

"It was helpful," says Mortensen. "You're in the natural environment, in the same climactic conditions that are pretty close to where the characters are at.

"It helps you to make that leap of faith that you have to make.

"The whole early part of the shoot was quite cold," Mortensen says. "It was so cold, it was hard to get through some moments and it added an emotional weight that might not have been there otherwise."

The film's Australian director John Hillcoat says his duty to the film's source material, McCarthy's much-praised novel, was to evoke not alienation but an eerie sense of recognition.

"It wasn't about the big event or the huge spectacle," Hillcoat says. "There was an immediacy and a sort of familiarity that we've seen or been here before but we can't put our finger on it."

To duplicate that sense of familiarity, Hillcoat digitally inserted smoke plumes from the World Trade Center attack into his world. Footage of ships washed up on a highway were taken directly from Imax footage of New Orleans two days after Hurricane Katrina hit. Most familiar of all, Hillcoat says, is the image of a lean, parka-clad Mortensen dragging a cart laden with all his worldly possessions.

"That's what happens with the homeless in every city," Hillcoat says. "That actually made the film more poignant."