Tippett Studio, meanwhile, did the treasure inside the vault (supervised by Matt Jacobs). All treasure mass was created for each of the shots, thus all practical effects were removed. They ray-traced the volume of metallic surfaces and managing the choreography of the mass for each shot proved challenging.

MPC was the other major vendor (supervised by Greg Butler). "We drew a virtual line through the school at the end of the courtyard," Burke explains. "The new viaduct where the giants battle the stone knights was MPC's work along with the hillside that attaches to it where Voldemort arrives."

MPC also created the CG crowds with nearly 1,000 Death Eaters and CG close-ups of the giants and the stone knights, which were treated as pure animation because they had to be robotic in their movements. "We did lots of studies of performance and stripped out the humanistic characteristics and turned them into automatons," Burke continues.

This is where they got into crucial sharing of assets as a result of the 3-D conversion (supervised in-house by Hugh Murray of IMAX and involving several vendors, including Pixel Magic, Sassoon, Animal Logic and Prime Focus). But there were also 300 CG shots fully rendered in stereo by the VFX companies.

 

Ron and Hermione run for their lives in this clip from the Room of Requirement sequence.

"There was obviously a learning curve challenge and it impacted the way the film evolved," Burke suggests. "We did a lot of shot sharing between different facilities, not even on the same continent, when you had one doing environments and another doing animation, and this became a logistical and creative challenge when you're doing everything in stereo and dictating who was going to set the stereo camera for each shot. We wanted to keep a consistent look to the film. So it added a great layer of complication for handing assets back and forth."

 

MPC additionally did the Room of Requirement sequence, which was much larger than the previous one because of the chase with CG fire creatures. "We built a large set and did a full-CG extension to that set and then switched to a full-CG set for flexibility with camera movements," Burke adds.

A chaotic river of fire was created using the Flowline simulation software licensed from Scanline. This combination of water and fire simulation also contained magical creatures that pursue Harry and his friends and try to trap them in the room.

Framestore did the King's Cross White Mist sequence when Harry encounters Dumbledore in the afterlife. :We texture shot the real King's Cross as the basis of the build and then crafted a white, ethereal environment and shot the actors on a white platform for them to walk up and down in and surrounded it with silks," Burke explains.

"You can see each year how the level of work progressed at each company and what their strengths were," Burke concludes. "There's plenty of continuing work with Hollywood: I just hope the London houses take advantage of the momentum and continue to improve, but don't over reach and blow it."

Bill Desowitz is former senior editor of AWN and editor of VFXWorld. He has a new blog, Immersed in Movies (www.billdesowitz.com), and is currently writing a book about the evolution of James Bond from Connery to Craig, scheduled for publication next year, which is the 50th anniversary of the franchise.