Christopher Nolan in 2018.
CNN  — 

Director Christopher Nolan created the look of a nuclear explosion for “Oppenheimer” without using CGI.

Nolan explained in a new interview with Total Film how he recreated the devastation of the first atomic bomb.

“I think recreating the Trinity test without the use of computer graphics was a huge challenge to take on,” he told the outlet. “Andrew Jackson — my visual effects supervisor, I got him on board early on — was looking at how we could do a lot of the visual elements of the film practically, from representing quantum dynamics and quantum physics to the Trinity test itself to recreating, with my team, Los Alamos up on a mesa in New Mexico in extraordinary weather, a lot of which was needed for the film, in terms of the very harsh conditions out there — there were huge practical challenges.”

Nolan also used a rotating hallway to film the big fight scene in “Inception” instead of using CGI.

He calls “Oppenheimer” a challenge but had help from an “extraordinary” crew.

“It’s one of the most challenging projects I’ve ever taken on in terms of the scale of it, and in terms of encountering the breadth of Oppenheimer’s story,” he said. “There were big, logistical challenges, big practical challenges. But I had an extraordinary crew, and they really stepped up. It will be a while before we’re finished. But certainly, as I watch the results come in, and as I’m putting the film together, I’m thrilled with what my team has been able to achieve.”

The film stars Cillian Murphy as J. Robert Oppenheimer, the physicist called the “father of the atomic bomb.”