Rogue One has been an absolute smash hit for Disney. It’s on the way to grossing $1 billion at the box office, and has earned positive reviews from critics and fans, but controversy did arise for its digital recreation of certain iconic characters. It’s been nearly a month since the movie was released and now we have a look as to what went into bringing these characters back to the Star War universe.

Note: There are spoilers ahead.

Nightline went to Industrial Light & Magic’s headquarters and sat down with producer John Knoll to see what went into bringing Peter Cushing’s Grand Moff Tarkin and Carrie Fisher’s young Princess Leia back to life. The main issue with faces is that we look at them all day, and thus we’ll notice even if something is slightly different. This is where most of the detail went in.

To recreate Tarkin, an actual actor (Guy Henry) had to get into costume and deliver the lines in the script. The scenes were shot live on set, and Henry’s facial performance was captured with a head mounted camera rig. From here, the visual artists took over.

A lot of workwent into recreating facial features

Guy Henry’s motions were transferred to a model of his face, and at this point, it was put into Tarkin’s likeness. To capture every detail of Tarkin’s face, John Knoll was able to track down a lifecast of Cushing’s face, which helped in recreation. Visual artists also had to watch the Grand Moff Tarkin scenes over and over to get really familiar with his movements. The entire process took nearly 18 months of work.

The same process was followed to recreate Princess Leia, this time with model Ingvild Deila serving as the actor on set.

You can check out the full video down below, it’s really interesting.