CFD Sinks Ships

By Thilmany, Jean

YOU MIGHT WORK WITH computational fluid dynamics software and yet not recognize its role on the silver screen.

“It’s an exhaustive task to prescribe the motion of every degree of freedom in a piece of clothing or a crashing wave,” said Ron Fedkiw, an assistant professor of computer science at Stanford University in Stanford, Calif.

He was speaking about computations used to make solids and fluids more realistic in computer-generated special effects for feature films. Fedkiw addressed the American Association for the Advancement of Science during its annual meeting held in San Francisco in February.

“Since these motions are governed by physical processes, it can be difficult to make these phenomena appear natural,” he told the group. “Thus, physically based simulation has become quite popular in the special effects industry. The same class of tools useful for computational fluid dynamics is also useful for sinking a ship on the big screen.”

This year, the special effects Oscar winner, Pirates of the Caribbean: Dead Man’s Chest, and a runner-up, Poseidon, both made heavy use of numerical simulation, Fedkiw said. Effects for both films were done by Industrial Light & Magic of San Rafael, Calif., which made its name in connection with Star Wars. Fedkiw has been a consultant to ILM for six years.

Most recently, one of Fedkiw’s creations-a physics-based modeling, or PhysBAM, core math engine-helped to create realistic water in Poseidon and Davy Jones’s tentacles in Dead Man’s Chest.

“The simulation of gases, liquids, and combustion for scientific reasons quickly translates into the ability to make animations of smoke, water, and fire,” Fedkiw said. “Similar statements hold for soft biological tissues, muscles, fractures, and other solid material problems. Once the scientific numerical simulations are worked out, interesting animations can be made shortly thereafter.”

Fedkiw also designs new algorithms for other applications, including CFD solid mechanics, computer graphics, computer vision, and computational biomechanics. The algorithms may rotate objects, simulate textures, generate reflections, or mimic collisions. Or they may mathematically stitch together slices of a falling water drop, rising smoke wisp, or flickering flame to weave realism into computer-graphics images.

CFD at the movies: Davy Jones’s beard of tentacles was created using the same kinds of codes that are used to understand real- world processes. The character is shown here in a promotional still for Pirates of the Caribbean: Dead Man’s Chest.

This section was written by Associate Editor Jean Thilmany.

Copyright American Society of Mechanical Engineers Apr 2007

(c) 2007 Mechanical Engineering. Provided by ProQuest Information and Learning. All rights Reserved.