Director Yates requested a much simpler Pensieve design so that it becomes much more of a surprise as you get into the memory.

According to Franklin, the idea for this sequence came as a result of Yates having a dream of the Millennium Bridge collapsing. It departs from the book by literally attacking the Muggle world and puts Harry Potter into the real world.

Double Negative worked on two other major sequences: the attack on the Burrow, which is also new to the film, and the Pensieve or Memory Bucket. "The Death Eaters attack the Weasley house in a new scene where we did quite a bit of fluid dynamics to create a wall of fire," Franklin continues. "Now it takes place in open marshland as opposed to the wooded area depicted in earlier films. My intention was to make it look like a localized firestorm appearing around the house. There's a fire snake again and we relied on a character animation approach while tweaking the Squirt toolset to get the appropriate movement.

Of course, the Ponsieve is the vessel through which memories are reviewed. "Yates required a much simpler design [this time] so that it becomes much more of a surprise as you get into it," Franklin suggests. "We made a very shallow, parabolic dish, which floats suspended in the air. This is activated by a vile of memory fluid. As the memory fluid is poured into the dish, it becomes a swirling cloud shape with strands of falling ink. It's almost like words on a printed page coalescing out of the ink. It was done in Squirt. We also used live-action elements by dropping ink into an aquarium."

Meanwhile, MPC specialized in both the Quidditch trials and the match. This is definitely something that has improved throughout the franchise. "I think Quidditch is a way of monitoring the change in computer graphics on Potter through the years," Burke says. "Perhaps it didn't look great in the early years and now we're getting a slightly more photorealistic look to the game play and the movement and digital doubles and environments. And we made a big effort on this one. David likened them to rugby matches in school on a wet, autumn day, in the mud -- that real, soaking wet, sodden environment. The first thing we thought we'd do is pay closer attention to the environment, including the stadium itself because I don't think enough attention has been paid to that previously. People have tried to get some exciting game play but not really help themselves to the way the environment affects the speed and the action of the camera movements. So we redesigned the environment and the stadium a little bit. We added more towers to give more of a backdrop to fly against and we created a much closer environment by introducing new mountains and a huge waterfall around the arena, so the stadium sat more in the middle of the bowl. This way by putting players against mountains or the stadium rather than the sky, they created a greater sense of speed. And MPC used a texture library of shots made in Scotland mapped them all together at a very high resolution to give us a complete and unrestricted world for flying. The trials were wet, misty, overcast day, and the match is played in snow for a different feel."

According to Nicolas Aithadi, MPC's visual effects supervisor, they reviewed aerial shows and motorbike races and tried to understand how to make Quidditch look more real. "One thing we found out was the advantage of using different lenses," Aithadi explains. "We used long lenses to flatten everything and have the camera catch up with the action. The other thing was to make it more exciting, there had to be more CG involved, so we had to find a way of handling all of those close-ups. What we did was we tried what we called videogrammetry, where we photographed the actor on a chair with four cameras. We had 68 tracking markers on the face and the riggers animated the CG face at the same time we were capturing the textures. The markers were small but we were able to get very good deformations in the face and textures. We used a very flat lighting environment when shooting to make sure we could use normal textures. This gave us something very real because the texture wasn't painted. It was straight from the film. We created blends to blend the four cameras and flattened them in UV space to get UV textures that were then sent to a shader. The CG work was so good, in fact, that it didn't require live -action takeovers.