The absolutely neat thing about the dinosaurs in the movie Jurassic
Park is that they possess enough artificial life so that they can be
reused as cartoon dinos in a Flintstones movie.
They won't be completely the same of course. They'll be tamer, longer,
rounder, and more obedient. But inside Dino will beat the digital heart
of T. Rex and Velociraptor -- different bodies but the same dinosaurness.
Mark Dippe, the wizard at Industrial Light and Magic who invented the
virtual dinosaurs, has merely to alter the settings in the creatures'
digital genes to transform their shape into lovable pets, while
maintaining their convincing screen presence.
Yet the Jurassic Park dinosaurs are zombies. They have magnificent
simulated bodies, but they lack their own behavior, their own will,
their own drive for survival. They are ghostly muppets guided by
computer animators. Someday, though, the dinosaurs may become
Pinocchios -- puppets given their own life.
Before the Jurassic dinosaurs were imported into the photo-realistic
world of a movie, they dwelt in a empty world consisting solely of three
dimensions. In this dreamland -- let's think of it as that place where all
the flying logos for TV stations live -- there is volume, light, and space,
but not much else. Wind, gravity, inertia, friction, stiffness, and all
the subtle aspects of a material world are absent and have to be faked
by imaginative animators.
"In traditional animation all knowledge of physics has to come from the
animator's head, " says Michael Kass, a computer graphics engineer at
Apple Computer. For instance, when Walt Disney drew Mickey Mouse
bouncing downstairs on his rear end, Disney played out on drawing paper
his perception of how the law of gravity works. Mickey obeyed Disney's
ideas of physics, whether they were realistic or not. They usually
weren't, which has always been their charm. Many animators exaggerated,
altered, or ignored the physical laws of the real world for a laugh. But
in the current cinematic style, the goal is strict realism. Modern
audiences want E.T.'s flying bicycle to behave like a "real" flying
bicycle, not like a cartoon version.
Kass is trying to imbue physics into simulated worlds. "We thought about
the tradition of having the physics in the animator's head and decided
that instead, the computer should have some knowledge of physics."
Say we start with flying logo dreamland. One of the problems with this
simple world, Kass says, is that "things look like they don't weigh
anything." To increase the realism of the world we could add mass and
weight to objects and a gravity law to the environment, so that if a
flying logo drops to the floor it falls at the same acceleration as
would a solid logo falling to Earth. The equation for gravity is very
simple, and implanting it in a small world is not difficult. We could
add a bounce formula to the animated logo so that it rebounds from the
floor "of its own accord" in a very regular manner. It obeys the rule of
gravity and the rules of kinetic energy and friction which slow it down.
And it can be given stiffness -- say of plastic or metal -- so that it reacts
to an impact realistically. The final result has the feel of reality, as
a chrome logo falls to the floor and bounces in diminishing hops until
it clatters to a rest.
We might continue to apply additional formulas of physical rules, such
as elasticity, surface tension, and spin effects, and code them into the
environment. As we increase the complexity of these artificial
environments, they become fertile ground for synthetic life.
This is why the Jurassic dinosaurs were so lifelike. When they lifted
their legs, they encountered the virtual weight of meat. Their muscles
flexed and sagged. When the foot came down, gravity pulled it, and the
impact of landing reverberated back up the leg.
The talking cat in Disney's summer of '93 movie Hocus Pocus was a
virtual character similar to the dinosaurs, but in close-up. The
animators built a digital cat form and then "texture-mapped" its fur
from a photographed cat, which it perfectly resembled except for its
remarkable talking. Its mouth behavior was mapped from a human. The
thing was a virtual cat-human hybrid.
A movie audience watches autumn leaves blowing down the street. The
audience does not realize the scene is computer-generated animation. The
event looks real because the video is of something real: individual
virtual leaves being blown by a virtual wind down a virtual street. As
in Reynolds's flocks of virtual bats, there is a real shower of things
really being pushed by a force in a place with physical laws. The
virtual leaves have attributes such as weight and shape and surface
area. When they are released into a virtual wind they obey a set of laws
parallel to the real ones that real leaves obey. The relationship
between all the parts is as real as a New England day, although the lack
of details in the leaves wouldn't work in close-up. The blowing leaves
are not so much drawn as let loose.
Letting animations follow their own physics is the new recipe for
realism. When Terminator 2 wells up from a molten pool of chrome, the
effect is astoundingly convincing because the chrome is obeying physical
constraints of liquids (such as surface tension) in a parallel universe.
It is a liquid in simulation.
Kass and Apple colleague Gavin Miller came up with computer programs to
render the subtle ways in which water trickles down a shallow stream, or
falls as rain on a puddle. They transferred the laws of hydrology into a
simulated universe by hooking up the formulas to an animating engine.
Their video clips show a shallow wave sweeping over a dry sandy shore
under a soft light, breaking in the irregular manner of real waves, then
receding, leaving wet sand behind. In reality it's all just
To make these digital worlds really work in the future, everything in
creation will have to be reduced to equations. Not just the dinosaurs
and water, but eventually the trees the dinos munched on, the jeeps
(which were digital in some scenes of Jurassic Park), buildings,
clothes, breakfast tables, and the weather. If this all had to happen
just for the movies, it wouldn't. But every manufactured item in the
near future will be designed and produced using CAD (computer-assisted
design) programs. Already today, automobile parts are simulated on
computer screens first, and their equations later transmitted directly
to the factory lathes and welders to give the numbers actual form. A new
industry called automatic fabrication takes the data from a CAD and
instantly generates a 3-D prototype from powered metal or liquid
plastic. First an object is just lines on a screen; then it's a solid
thing you can hold in your hand or walk around. Instead of printing a
picture of a gear, automatic fabrication technology "prints" the actual
gear itself. Emergency spare parts for factory machines are now printed
out in hi-impact plastic on the factory floor; they'll hold out until
the authentic spare part arrives. Someday soon, the printed object will
be the authentic part. John Walker, founder of the world's premier CAD
program, AutoCAD, told a reporter, "CAD is about building models of
real-world objects inside the computer. I believe in the fullness of
time, every object in the world, manufactured or not, will be modeled
inside a computer. This is a very, very big market. This is everything."
Biology included. Flowers can already be modeled in computers.
Przemyslaw Prusinkiewicz, a computer scientist at the University of
Calgary, Canada, uses a mathematical model of botanical growth to create
3-D virtual flowers. A few simple laws apparently govern most plant
growth. Flowering signals can get complicated. The blossom sequence on a
stalk may be determined by several interacting messages. But these
interacting signals can be coded into a program quite simply.
The mathematics of growing plants was worked out in 1968 by the
theoretical biologist Aristid Lindenmeyer. His equations articulated the
distinction between a carnation and a rose; the difference can be
reduced to a set of variables in a numerical seed. An entire plant may
only take a few kilobytes on a hard disk -- a seed. When the seed is
decompressed by the computer program, a graphical flower grows on the
screen. First a green sprout shoots up, leaves unfurl, a bud takes
shape, and then, at the right moment, a flower blossoms. Prusinkiewicz
and his students have scoured the botanical literature to discover how
multiple heads of flowers bloom, or how a daisy forms, and how an elm or
oak fork their distinctive branches. They have also compiled algorithmic
laws of growth for hundreds of seashells and butterflies. The graphical
results are entirely convincing. A still frame of one of Prusinkiewicz's
computer-grown lilac sprays with its myriad florets could pass for a
photograph in a seed catalog.
At first this was a fun academic exercise, but Prusinkiewicz is now
besieged with calls from horticulturists wanting his software. They'll
pay a lot of money if they can get a program that will show their
clients what their landscape designs will look like in ten years or even
The best way to fake a living creature, Prusinkiewicz found, is to grow
it. The laws of growth he has extracted from biology and then put into a
virtual world are used to grow cinematic trees and flowers. They make a
wonderfully apt environment for dinosaurs or other digital
Brøderbund software, a venerable publisher of educational software for
personal computers, sells a program that models physical forces as a way
of teaching physics. When you boot-up the Physics program on your
Macintosh you launch a toy planet that orbits the sun on the computer
screen. The virtual planet obeys the forces of gravity, motion, and
friction written into the toy universe. By fiddling with the forces of
momentum and gravity, a student can get a feel for how the physics of
the solar system works.
How far can we press this? If we kept adding other forces that the toy
planet had to obey, such as electrostatic attraction, magnetism,
friction, thermodynamics, volume, if we kept adding every feature we saw
in the real world to this program, what kind of solar system would we
eventually have in the computer? If a computer is used to model a
bridge -- all its forces of steel, wind, and gravity -- could we ever get to
the point that we could say we have a bridge inside the computer? And
can we do this with life?
As fast as physics is encroaching into digital worlds, life is invading
faster. To see how far distributed life has infiltrated computational
cinema, and to what consequences, I took a tour of the state-of-the-art