Seven Harry Potters
“The first thing we needed to do for this scene was to achieve the transformations of the other characters into Harry Potter. While they’re transforming, they’re full CG characters. We used this technique, this new facial capture technique called Mova, which uses ultraviolet makeup. It allows you to capture real time facial expressions during the performance from the actor.We used it to capture the expressions of the actor who was becoming Harry Potter so we had their reactions to when you’ve drunk Polyjuice potion then used the original performance of the actor to drive that so the characteristics of the behavior was the real actor. It was great that those impressions came through and it doesn’t just look like seven Dan Radcliffes.
We did these little transformations, then when we got through to the seven Harry Potters, we used Dan Radcliffe seven times. We used a motion control camera to film him seven times. To convince people hat there were different people inside a Harry Potter-looking body, for each shot we rehearsed what was going to happen with each of the real actors. Dan would study the way each of them behaved and would mimic the way they acted, copying their performances. He really got into the character of each one of them and then we would shoot separate passes and combine each of those layers afterwards into the computer. It was a very long, complicated thing to shoot. Each pass for Dan playing the other actors was at least ten takes, so we ended up doing up to 70 takes for each shot, which was obviously incredibly difficult for Dan, but he’s a great actor.”
(More on Techland: A Harry Potter Style Invisibility Cloak Is Possible, Science Says)
The Escape From Privet Drive
“The supernatural world is invading the muggle world. We start with the big fight in the air, which is a lovely CG environment, but David Yates really wanted to do a James Bond, Bourne Supremacy-type car chase right in the middle of this thing – even the “going down the tunnel the wrong way” idea. We spent six months pre-visualizing all of this big sequence, basically working out all of the action. It was complicated further by having Hagrid and Harry in the shots – Hagrid’s played by Robbie Coltrane who isn’t actually a giant and every time you see them he has to be scaled and put back into the same shot.
We did as much in-camera stuff as possible using stunt men to really try to get some great moments. We used an old airstrip, a runway near the studio and had a stuntman for Hagrid and Harry and stunt drivers. We filmed for a week of nights, shooting as many stunts as we could get. We created a CG version of Dartford Tunnel to digitally drop in around them and did face replacements. If we got into a big close up with Dan maybe firing his wand, we did that back on the stage with a green screen, with Dan in a sidecar that was sitting on a big motion base, which would allow it to turn and twist as if it were really being driven along. We did end up turning a real bike upside down so there were real shots of Dan hanging upside down out of the sidecar. But we added the CG backgrounds in but shot them all and then put them all back together again.”