Digital water sends vfx sparks flying
Fluid simulations shine even with no H2O
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Long a task that challenged computer scientists and digital moviemakers, water simulation has made rapid advances in recent years, ramping up its 'wow!' factor through "The Day After Tomorrow," "Poseidon" and into this year's visual effects and animation nominees, "Pirates of the Caribbean: At World's End," "Surf's Up" and "The Golden Compass."
The technology behind the imagery also has earned the Academy's attention, with six of the 10 Scientific and Technical Achievement Awards for 2008 going to fluid simulation-related work.
What makes fluid simulations hard is not just the complex physics involved, it's the need to alter the simulation so the water follows the script without offending audience's natural ability to detect even the slightest bit of fakery.
The difficulties of working with CG water led ILM visual effects supervisor John Knoll to avoid it as much as possible on the first two "Pirates" films. Knoll had hoped the work ILM had done for "Poseidon" would be up to the task of the third film, only to realize there was no way around it this time.
"Once we got to 'Pirates 3' and we had the edge of the world, the capsizing of the Black Pearl and the maelstrom, there was really no good way to do those sequences with real practical (water effects)," he says.
Knoll used ILM's inhouse fluid simulation system -- which works within the company's Zeno software and was honored with a Scientific Engineering Award by the Academy -- to create the very high-resolution images needed for the maelstrom. Nick Rasmussen, a member of the award-winning team, says the system was able to handle the massive simulations required by breaking them up and spreading them across multiple processors.
Although it's done with a stylized look, the fluid simulation on "Surf's Up" benefited from animation's ability to take some liberties with the look of water, despite having to meet a standard of realism, says the film's VFX supervisor, Rob Bredow. "Water can only look a certain way, and if you stylize it too much, it doesn't look like water," he says.
Fluid simulation is used for more than just water. For example, the effect used in "The Golden Compass" for the disintegration of the animal daemons may appear to be a cloud of sparks, but the movement of that cloud is made with a fluid simulator.
Bill Westenhofer, who supervised Rhythm & Hues' work on the effect, says overall supervisor Mike Fink had requested an organic look that other kinds of particle simulators couldn't create.
"With a fluid simulation, stuff kind of flies together; it swirls and eddies," he says. "The particles will flow over the top of a person, and you get a much richer result."
But while the technology has definitely advanced, it's taken a lot of work and a lot of collaboration -- and is still far from easy, says Jos Stam, a member of the team whose work on the Maya Fluid Effects system received a Technical Achievement Award.
Doug Roble, part of Digital Domain's Scientific Engineering Award-winning team, agrees. "It hasn't been just us, it's been the entire community that's been pushing forward," he says.
TIP SHEET
What: Scientific and Technical Academy Awards Dinner
When: 6:30 pm. Saturday
Where: Beverly Wilshire Hotel, BevHills
Web: oscars.org
