Captain America: Civil War editor Jeffrey Ford, visual effects editor Dan Deleeuw and sound editor Shannon Mills spoke during a Q&A (via IGN) about the process of de-aging Robert Downey Jr. for the flashback sequence in the film. The highlights are below:
Deleeuw on how they came up with the initial pic of younger Tony: “Basically what we did. we went through and we put a kind of catalogue together of his earlier films. Part of the process was deciding what Robert should look like, as this younger version of himself. And we settled on kind of a mix between a couple films. It became more of a young Stark, than a young Robert, in a way.”
Deleeuw on morphing the new composite into the performance capture: “…you actually take Robert’s face and warp it. You’ll go into your computer and you’ll take his face and basically massage it so areas as you age, that we’ve all experienced, you know, that kind of distort from when you were young—then kind of distort those back to when you were young, at an earlier age…[and then] the imagery you’re working from, there’s a fine level of detail and as the face gets warped, a lot of that detail gets washed away. So then what you’ll do is you take a double, fairly close in facial structure, but then you’ll photograph that double in the same positions, [for example] how the face is oriented to camera. And you’ll steal detail from that younger person’s face, then reapply it to Robert’s face. And then you go and do clean ups on the hair.
Ford on the length of the shot being a challenge: “Part of what made the shot even more challenging was the length of the shot. The idea that the guys wanted to do it as a ‘oner,’ one long shot. You kind of wanted to set up the idea that there is something off about the scene. He comes out and as it plays longer and longer—if it played like a normal scene, you would have cut. Normally that helps us out because if it’s a shorter shot, you can split that up between more people and get the work done quicker.”
Mills on getting Downey’s voice de-aged: “…when we did it. We realized we had to pitch him up just slightly, but very little, because Robert, he acted it, too. It’s one of those things—it’s a combination of incredible visual effects, but also acting, because he performed it. He had to be that guy for that moment as well, because all the technical stuff in the world isn’t going to work if he didn’t act that. If these guys didn’t get a performance out of him. It’s that combination of those things.”