The bunker was bathed in warm orange light, the Man and the Boy enjoying the long-gone comforts of civilization: bunk beds with pillows and sheets, a slice of frosted cake and a fork, even the fixings for a hand-rolled cigarette and gulp of alcohol.

Yesterday, actors Viggo Mortensen and young Kodi Smit-McPhee were in the old Benkovitz warehouse in the Strip District shooting their final Pittsburgh scenes for the movie The Road.

Crew members were dismantling sets and moving out gear even as they played freeze tag - stopping in their tracks or cursing their squeaky shoes - once director John Hillcoat started shooting into the bunker that is a rare, welcome haven in a post-apocalyptic world.

The exterior was in New Galilee but the interior had been built on a makeshift stage and outfitted with collapsible canvas chairs, a table and what novelist Cormac McCarthy called "the richness of a vanished world."

That meant blankets, jars, cans and boxes of food, candles and an out-of-sight flare of fire lending a gorgeous glow, courtesy of cinematographer Javier Aguirresarobe.

"This is rare," Mr. Mortensen said after a morning and early afternoon of scenes shot from this angle and that. He climbed out of the upper bunk, coughed (in character) enough to make the chests of onlookers sting and shared a meal with his boy.

"It's a very nice moment but very rare in the story. ... Usually our scenes involve physical hardship and are emotionally challenging, mentally difficult a lot of times," he said.

"We were lucky with the weather, all the exteriors we were shooting early on, we had that bad weather - we had the snow, we had the rain, we've had mud, we've had a lot of cold, so the look is right," he added.

As the trees sprouted blossoms, the movie shifted inside.

After filming on closed roads near Breezewood, in Saxonburg, New Galilee, Raccoon Creek State Park, Braddock, McKeesport, the Strip and in coal country, the production pulls up stakes today. It heads to Lake Erie, New Orleans, Mount St. Helens and Oregon, where flashbacks with Charlize Theron will be shot.

As for Mr. Mortensen's look, the beard that was in the early stages on the Oscar red carpet is in full flower. It distracts from his gaunt cheeks, an authentic part of his character who is starving in a world where a few raisins or can of fruit is a rare treat and where desperation has turned some survivors into cannibals.

His mismatched clothes and hole-pocked socks are those of a homeless man, his belt cinched around a shrinking waist. When he and the Boy - as the characters are called - find the bunker, both are able to clean up but the Man never lets down his guard or his gun.

Mr. Mortensen and Kodi, an Australian honored for his turn in Romulus, My Father, bonded over a Bucs-Reds game, the resonant themes of "Bodies ... the Exhibition" at the Carnegie Science Center and their many shared scenes.

The Eastern Promises and Lord of the Rings star praised his young co-star's technical skills, natural presence, intelligence and versatility.

"It's a luxury for me as an actor to have a partner - most of the time it's just the two of us - who's so good at playing, who has such a good game," said Mr. Mortensen.

The Road is very much the story of parents and children and lessons passed from one to the other. Mr. Hillcoat has a 6-year-old boy, Kodi reminded Mr. Mortensen of his now-grown son, and when Mr. Mortensen called Mr. McCarthy to chat, talk turned to their sons.

In separate interviews, Mr. Mortensen, Mr. Hillcoat and unit production manager Buddy Enright volunteered praise for local crews and residents, the city and state - its tax incentive is working - and the Pittsburgh Film Office.

They singled out visits to Fallingwater, a behind-the-scenes tour of the Pittsburgh Zoo & PPG Aquarium, family-owned restaurants, the Strip District and other thriving touchstones to Pittsburgh's past as highlights of their stays.

As for the movie that brought them, it's faithful to the spirit of the book, Mr. Hillcoat said.

"In our world that we're creating, we're not saying everything is just literally covered in ash. There's more variation in the devastation on a visual level," with ash, snow, water, fallen trees, lightning, fires and earthquake tremors factoring into "a world in severe trauma."

Like the novel, the screenplay by Joe Penhall doesn't specify the trigger to this trauma.

"That's what makes it more realistic, then it immediately becomes about survival and how you get through each day as opposed to what actually happened," Mr. Hillcoat said.

Flashbacks and the bunker interlude highlight "all the little things we take for granted, certainly in the comfortable, more affluent parts of the world," the director said. But the father and son are the movie's heart.

"The book had a huge impact on me, it affected me more deeply and more profoundly than almost anything I've ever read," Mr. Hillcoat said. "That's partly because I'm a father of a gorgeous 6-year-old boy" and mindful of what's happening in the world.

Growing up in Canada in the 1970s, the native Australian worried nuclear war was inevitable.

"Quite seriously, I never even thought I'd get to the age of 40 as a kid, as a teenager at least," he said.

But he did and he's making a movie that explores humanity and hope in a seemingly hopeless world and a father who teaches his son to "carry the fire," as Mr. McCarthy so eloquently phrases it.