Technology: Volumetric
Effects Nominee: Alan Kapler | Digital Domain Storm
Credits: The Day after Tomorrow, Lord of
the Rings: The Fellowship of the Ring,
XXX
In 2004’s The Day after Tomorrow, the
science is silly—an ice age descending in days?—but the
climatic havoc is sublime. Grapefruits of hail bombard Tokyo.
Floods ravage New York. Out-twistering Twister and
out-storming The Perfect Storm, the movie wowed
audiences as it established a new benchmark for disaster on
film.
The Zeus behind much of the mayhem was Sci-Tech
Award winner Alan Kapler. As a technical director at Venice,
California–based special-effects house Digital Domain, he
invented Storm, software that aids designers in generating
some of the trickiest visual effects in the business:
volumetrics. “Things with hard and defined surfaces, like
monsters, are fairly easy to represent in a computer using
geometry,” Kapler says. “But wispier things like clouds, mist
and water are incredibly difficult.” Storm excels at rendering
these ethereal forms with high-resolution depth, shadowing and
lighting. The program also helps to simulate natural events
such as avalanches—like the one in the 2002 Vin Diesel action
fest XXX—with a real-world mix of control and chaos.
The result is bigger thrills for moviegoers, and fewer ulcers
for effects gurus.
“Everything I do in computer
graphics tends to be nature-based,” Kapler says. For fun, he
creates programs to generate seashells, snowflakes and leaves;
between movies, he sets off in his van for northwestern Canada
or Alaska to hike and fish. In The Day after Tomorrow,
his passion for natural phenomena paid off.
To produce
the flood sequences, the Digital Domain crew shot 40,000
photographs of Manhattan streets and buildings, assembled them
digitally, and then used the company’s hydrodynamic simulation
program to bombard the city with the electronic equivalent of
Noah’s flood. And that, in some ways, was the easy part.
The key to making the big flow believable, Kapler
says, was the little details—whitewater surging forward,
tendrils of liquid exploding skyward, thousands of droplets of
spray and mist. To sketch out this aquatic action, the effects
team ran “particle” simulations, generating flows of dots that
moved semi-randomly, with parameters to govern water current
and velocity and to mimic the effects of wind and gravity. The
results were then plugged into Storm, which transformed each
particle into a cluster of larger 3-D pixels called voxels.
This alchemy is the software’s essential breakthrough.
Computers can handle only a few hundred thousand particles
before overloading; Storm’s voxels conjure an image with
billions of apparent particles.
Kapler didn’t invent
voxels, but he devised the memory- saving compression routines
that first allowed them to be used on the scale necessary for
big-screen effects. He also made Storm user-friendly. After
the artist feeds a few rough instructions into the computer,
it uses Kapler’s algorithms to create a seeming infinity of
interconnected droplets, each with its own color, shape and
internal movement. And he made Storm intelligent, capable of
determining where each voxel of water stands in relation to
the light source and which other voxels stand in the way. In
The Day after Tomorrow floods, water in the main
channel appears dark, churning whitewater semi-opaque, and
airborne mist virtually transparent. Manually making such
lighting and shadowing determinations for each water speck
would be like relocating the Sahara with tweezers.
All
of this illustrates the irony of visual effects—that some of
the simplest things in nature are some of the most complex to
synthesize. “We’ve spent our whole lives exposed to water,
snow, smoke and dust,” Kapler says. “If they aren’t shaped
right, don’t move right, or the shadows aren’t correct, your
brain sends you a subconscious message: bad special
effect.”
Digital
Domain
Storm software uses 3-D pixels called
voxels tto create the billowing, edgeless forms found in
nature.
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