fxg: Hogwarts was such a big part of this film – how did you plan out that work given that it would be such an enormous digital creation?

Vickery: It was definitely the biggest thing we had to do – we started working on it in summer 2008 and we were still working on Half-Blood Prince at that point. Tim Burke (the overall visual effects supervisor) and the director David Yates were very keen to see whether it was plausible to do a digital Hogwarts, to free them up in filmmaking terms. We went on set and photographed the miniature before it was deconstructed. Then we started doing tests to show the client that a CG believable Hogwarts would work in both wide shots, full close-ups and as set extensions. That was the easy part in a way. The difficult part was then taking that and creating an asset that could be used in the film. When we were building our asset, we still had no idea what any of the shots would be. They also didn’t really know at that stage how much set they would be building.

fxg: So where did you start with modeling Hogwarts?

Vickery: Ultimately we were tasked with building this asset that was essentially seven miles from one end to the other, with a completely digital school in a completely pristine state and a destroyed state. We weren’t sure how close we were going to get to any of it. But we had to prepare for it both in terms of the environment and in building the asset. I think one of the cleverest things we did was that our lead environment artist – Pietro Ponti – was tasked with going to Scotland where they shot the mountains surrounding the school and capturing that data. He set up a three-camera rig, left, center and right. The cameras were all set up with remote trigger shutters. He went up in a helicopter and they would fly semi-circular flight paths around every single mountain they needed to capture, at different heights.

Pietro plotted all these points out using Google Maps and Earth, so that before he went he was able to work out the best time of day depending on the time of year they were shooting, so that they got the best lighting for every mountain. The helicopter pilot was really great and also super-excited that Pietro had managed to do all of this GPS work. They just fed the co-ordinates into the helicopter nav system and just flew perfect positions all the way around the sides of these mountains. It was an amazing little trick.

We got all of this information back at Double Negative, and used a piece of software called Photo-fit, which is a photogrammetry tool we used to re-create the mountains. Once we had all the mountains, we worked closely with Stuart Craig, the production designer, and he created a collage of geometry surrounding the school and we could put the mountains anywhere we wanted. The next tricky thing was actually just modeling the school. In the end we had a team of about 30 people working for two years building the school. It was fully pristine and brand new, but then also torn to pieces.