world gets a dose of reality |
LOS ANGELES -- The gangly skeleton pauses at the top of the
staircase and then fearlessly dives headfirst, crumpling in an
apparently bone-jarring fall.
Petros Faloutsos chuckles as he replays the clip on his laptop
computer. Again and again, the UCLA scientist commands the virtual
character to dive.
The animation is primitive, the technology complex. Physics, not
the computer animator's mouse, controls the action.
Although just a prototype, Faloutsos believes his animation
program will one day allow virtual stunt artists to replace their
flesh-and-blood counterparts in performing otherwise deadly feats of
"Maybe people will be directing virtual actors, and we'll have to
give them Oscars, too," Faloutsos mused.
The brief clip is a glimpse into the nascent field of
physics-based animation. The technique, whether used for movies or
video games, strives to create a virtual world guided by the same
physical laws that give order to the real world.
"It's the Holy Grail of character animation. Everybody wants to
do it, but there's not a whole lot of it out there right now," said
Damien Neff, senior artificial intelligence designer for NFL Fever
2002, a Microsoft video game that makes limited use of the
As the technology matures, real stunt artists have mixed feelings
about the impact they believe it will increasingly have on their
"There's a positive side and a negative side: To talk positive,
it's made it safer to do a stunt -- you don't have to lay your neck
out on the line as much as you used to. But it's taken some cash
away also," said Ben Scott, a Hollywood stuntman who works on the
HBO series "Six Feet Under."
Traditionally, animators have relied on their own talents to draw
characters that appear to move naturally. Movie studios and game
developers also bank increasingly on libraries of hundreds of stunts
amassed by filming the sensor-studded bodies of real performers.
Those captured motions can then be matched to virtual characters
and inserted into movies or games, where they appear real as they
move within environments like sinking ships or burning buildings
that could put real actors at risk.
Animation systems such as that created by Faloutsos and his
former colleagues Michiel van de Panne, Demetri Terzopoulos and
Victor Ng-Thow-Hing attempt to trump both. The key is using
mathematical formulas that only loosely choreograph the movements an
animator wants a character to undertake.
Command, say, a character's arm to move and the momentum will
force its torso and head to shift as well.
The range of motions available to a character ultimately guide
how it behaves, as does its own computer-generated sensitivity to
both gravity and any forces imparted by its virtual surroundings.
Different environments, for example, will prompt the same
character to move differently -- and unpredictably. A fall on slick
ice won't be the same as one down a steep flight of stairs.
In the forthcoming film "The Time Machine," Digital Domain used a
physics-based animation technique to render the collapse of
thousands of skeletons of people turned to dust and bone.
Animators still shy away from using physics to model the movement
of people, however. They say the human eye is just too good at
spotting even the slightest hint of fakery.
But Faloutsos believes future systems will allow directors to
guide characters as they do live actors.
"The ultimate goal is to have a totally complete human inside the
computer that you can direct," he said.
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