Avatar: The Game Changer
ILM, in fact, focused on vehicle-oriented shots, which numbered around 250, according to Letteri. These included the shuttle, the Samson, the Scorpion and the Dragon helicopters and the AMP suit. Scenes included the opening fly over the Pandoran jungle, the shuttle re-entering and landing on Hell's Gate, the first glimpse of the floating mountains, the vehicular assault on the Hometree and parts of the explosive climax.
"For the most part, all of the vehicles were designed and textured by Weta, so we built them up to parity of look," explains John Knoll. "The only exception was the Dragon, Quaritch's big helicopter. They built the model but hadn't textured it, so we did the texturing here.
"One thing that did complicate every aspect was stereo. Everything had to work properly in depth. Our matchmoves had to be very precise because just looking good in screen space wasn't sufficient. So you have to make sure that you match your focal length precisely and you're doing very accurate tracks on a lot of features. So you have to pass very high quality data in.
"One of the big breakthroughs for us was the explosions. In the past, we've done explosions by doing elements, but given Cameron's request to exactly match the templates and the need for the explosions to interact with other CG objects, the best solution was CG. How far can we push CG explosions to look good enough in close-up? TD Chris Horvath, who was instrumental on the fire on Harry Potter and the Half-Blood Prince, was responsible for the shading side of the solution."
The explosions are fluid simulations using the same engine ILM used for The Maelstrom and Poseidon. However, there were modifications to the engine "so that it behaves appropriately as gas expansion volume and to carry around temperature attributes. And the shader takes the whole volume density grid and makes it look like fire. Chris learned a lot from Half-Blood Prince. There's that whole black body radiation curve that you want to use so that your fire has all the right colors and color gradience in it. I think having a tool that lets you custom tailor a high quality explosion that has controllable behavior and can tightly interact with CG objects is going to be an important thing for us on future shows."
Letteri agrees there will be much to be learned from Avatar: " I think what everyone discovered as you went along is that if you're going to put a virtual stage together like a live-action shoot, then this becomes the front end to a visual effects piece. Because you not only start thinking in terms of takes and selects, but as shot design. You have to be able to switch from one to the other. And it requires a level of infrastructure for the whole thing that I think is going to benefit everyone if we can come up with some system across the board to make that easier."
Bill Desowitz is senior editor of AWN & VFXWorld.