A Potter Finale Fit for a Wizard

An all CG Hogwarts is one of the many vfx highlights of the Harry Potter finale. All images © 2011 Warner Bros. Ent.

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They certainly saved the best for last: The full-CG Hogwarts, the thrilling Gringotts break in and escape on a dragon, the Room of Requirements escapade with fire creatures, the battles, the ethereal encounter with Dumbledore and the final confrontation with Voldemort. Plus 3-D for the first time.
"Environments, especially, have been a breakthrough, asserts Tim Burke, the overall supervisor that has been on Potter since the second film, The Chamber of Secrets." It's all HDRI, and that way of photographing textures has given us incredibly detailed shots and the ability to relight things. It's all based on the proprietary tools to stitch this stuff together and make it work."
But the biggest decision was making Hogwarts CG for the first time. Double Negative and MPC split up the school and surrounding environments, and spent 18 months just on the design. "Basically, we were able to design and execute shots right up to final delivery," Burke adds. "It gave us a lot of flexibility. We were able to render things quickly without fussing around. It seems to me that we can turn around iterations so much quicker than ever before."
Since the ongoing war takes place at Hogwarts throughout the second-half of Part 2, it was essential that the battleground display sufficient detail and dynamic compositions, especially in light of the 3-D.
"David wanted to create these fantastic, big shots that link different parts of the action in different areas, going from outside the school to inside the school," Burke adds. "And all of the development that we've done and the extra high-resolution that we've corrected for have allowed us to fly around courtyards and into windows during critical moments of the battle, and has made the whole experience very visceral and given the camera a way of being immersive."

Harry and friends take a ride out of Gringotts on the back of a dragon.

Establishing this world around Hogwarts was part of the full-CG process because we see Voldemort and his army arriving on one side of the school and the stone knights (an homage to Ray Harryhausen) coming to life and defending the school on the other. The choreography of sequences required nine months of previs in-house and produced more than a half-hour of finished footage that Yates used to cut his sequences with. Thus, he had a complete film made up of drama and previs.
Double Neg (supervised by David Vickery) was the lead vendor and the equivalent of the miniature model facility, only in CG. They started building the school and surrounding environment at the end of 2008, led by Pietro Ponti, the environment supervisor. Their work includes the battle of Hogwarts and wooden bridge attack. They also did the first sequence, where Harry and his friends break into Gringotts bank, have the wild cart ride into the cavernous vault and then escape on the dragon. Burke particularly likes the forlorn look of this imprisoned creature, which distinguishes it from other dragons.