John Knoll worked double duty on Rogue One: The chief creative officer at ILM first came up with the story for the new Star Wars spin-off film and then oversaw the blockbuster’s enormous visual effects department.

Rogue One was perhaps the most complicated Star Wars film from a VFX perspective to date. ILM has paved the way in developing cutting edge technologies over the last 40 years, coming a long way from the miniatures and models they rigged up on the fly in a warehouse during the production of A New Hope. But having all the resources in the world was actually a potential handicap, since Rogue One had to recreate the look and feel of the 1977 original. Knoll and his team put a lot of work into making sure Star Wars fans didn’t notice a single difference. With the film being a critical and financial success, Knoll spoke to Inverse about how they were able to solve the many complicated problems set before them and the limits of the technology they have pioneered.

There’s been a lot of talk about the way you recreated Peter Cushing and Carrie Fisher via motion capture and face replacement. How far do you think we are from not even needing an actor to put the face on? Can it be full animation?

Oh, you need an actor. I want to clarify that it’s not so much that that’s a CG character. Tarkin was played by Guy Henry. We cast a really good actor who played that role on set. I think a way to think of it is — the way we were thinking about it — is that you were casting an historic figure in a movie. And there are historic figures who you don’t know what they look like, and you get away [with] casting anyone you think is appropriate for it. And then there are historic figures that we’re very familiar with their image, whether you’re doing Nelson Mandela or John F. Kennedy. So that narrows down the actors you’re able to cast in that role. Often, some kind of effort is made to make that actor look more physically like the person they’re playing, whether it’s with makeup or full-on prosthetics.

What we did was not conceptually any different than doing something like that. We cast an actor who played the Tarkin role for us, and rather than using makeup to transform the appearance, we use computer graphics.

So you never think there will be a moment where you don’t need a live actor at all?

Well, the acting needs to come from somewhere.

There are CG-animated characters.

But I would say Pixar is not a conspiracy to get rid of actors. The actors are still very much involved. In the case of the animated picture, the animators are the actors. They’re making all those choices about performance. In this case, by partnering with Guy Henry as the character, he was making all those acting choices. The work we do afterwards is really one of interpreting his performance and making sure it stays on model and that it works well on the Tarkin character.

Did it help that he was stationary a lot? Tarkin stands straight and gives orders. Would it be harder if he had been an action hero?

No, it’d have been easier. The more they moved, the harder it is to pin them down and get a good look down at them. If they’re just standing there and talking reasonably close to the camera, you get more opportunity to examine the fine details of what makes a person really believable as a human being.

Doing face replacement on a stunt performer in an action scene, that’s something we’ve done pretty significantly on a lot of projects. A lot of people don’t notice it’s being done. It’s a lower bar than a close-up performance. A quiet acting moment is always going to be harder to do than a bloody battle or some other kind of action sequence.

The new Death Star in 'Rogue One' Lucasfilm

You had to recreate a lot of things from the original movies via new technology, not just people. And in the prequels, things didn’t look old, and it was set before A New Hope. How did you capture that grittiness in a way that the prequels weren’t able to?

Some of it is passage of time — the tools have gotten a lot better. And it was also very deliberate, knowing it had to be very close to the look and feel of Episode IV. The overriding philosophy was to try to match how you remember Episode IV more than how it may actually have been. In terms of things like lighting design and shot design, it actually doesn’t match that well. But we pulled all the things that are your salient memories of those places and vehicles and managed to bring back that memory, so hopefully they can feel true and matches right up.

Technology has changed, so the things that were physical prop models in A New Hope are now made digitally. What was the hardest thing to accurately recreate?

One of the things I was keen to do was really illustrate the scale of the Death Star. It’s supposed to be 100 miles in diameter, and there are very few shots in the original that really show you how big that was. So we designed a shot when Krennic’s shuttle leaves the Death Star. It’s not quite a Powers of Ten shot, but you see his shuttle that just left the docking bay in the equatorial trench, and the camera keeps pulling back and tilting up. I was pretty pleased with how that turned out and I think it gave you a pretty good sense of how big that object really is.

That proved to be a really hard shot to do. We are depicting a scale of a Death Star that hadn’t been shown before. In the original film, it was shown as a spherical model, and a really tight close-up with those modular tiles. But we’re showing a scale halfway in between, and really marrying the aesthetics of all of those, that was a tricky thing to get right.

So how’d you do it?

For a lot of modelers and matte painters and art departments it was really going to [original production designer] Ralph McQuarrie school. We studied a lot of his design work to see how he did what he did. He painted the original three foot model of the Death Star, and there was a language to the line work that he did. He did a matte painting that was sort of a middle scale view. It’s in a couple of shots, to try to bridge the medium and close angles. A lot of paneling that he put into that matte painting, they seem random, but it really isn’t. There’s a very subtle and sophisticated design language in there that we referred to over and over again. As people were taking cracks at trying to show what some of the panels should look like — “This series of panels is four and a half miles tall, what level of detail should be in it?” — I kept pointing them to this McQuarrie painting. I [always] loved his work, but I have a newer and more profound respect for the brilliance for his design.

In A New Hope, we only see the Death Star obliterate a planet from space; we’re almost disconnected. In Rogue One we see the damage from the ground level, and it looks like a nuclear explosion. Was that parallel done on purpose?

Yeah, some of the larger themes in the film are about the morality and ethics of a weapon of mass destruction like that. A nuclear weapon infantry is not an outlandish idea to introduce here. Obviously, the big difference is you never saw the Death Star firing down from the view of a planet’s surface. Previously, it had been depicted at full power, where it just completely obliterates a planet. But this idea of doing a low-power hit that destroys just a localized area seemed like an intriguing thing to be able to see from the ground level. You’d think any massive release of energy like that would have a lot in common with nuclear testing.

This interview has been edited for brevity and clarity.