HOW IT WORKS
Building Character, Wrinkle by
Wrinkle, in a 3-D World
By MICHEL MARRIOTT
Published: May 13, 2004
S Hollywood action films are increasingly spun off
into video games, game developers are facing more pressure to squeeze
greater realism into their computer-generated characters and
environments.
Maintaining the illusion of reality is crucial in
the transformation from movie screen to video screen, developers say.
And while improvements in microprocessors and graphics chips have
helped advance game imagery over the years, the more significant
breakthrough has been in software, said Peter Wanat, executive producer
of the coming video game The Chronicles of Riddick: Escape From Butcher
Bay, for Vivendi Universal Games.
The improvements have been in the form of a 3-D
graphics technique called normal mapping. The technique, Mr. Wanat
said, permits game designers to create finely detailed virtual worlds
that can change as the game is played without overtaxing the computers
and consoles that run them. (The word "normal" refers to a vector, or
line, that defines which way one face of an object is pointing.)
Mr. Wanat described normal mapping, sometimes called
polybump mapping, as a "significant evolutionary jump" in game design.
Andy McNamara, editor in chief of Game Informer, a monthly game
magazine, went a step further. "Normal mapping is a glimpse into the
future for consoles and PC's," he said. "Games can be far more
complex-looking."
When normal mapping is used, game artists can first
create a richly detailed model - a hero's dimpled face and wrinkled
clothing, say, or a bullet-riddled prison wall - by using millions of
polygons, the basic construction elements of a video game. Then special
software is used to translate, or map, all that rich detail onto the
same object in a model made with far fewer polygons. The result is a
realistic-looking object that, because it is made up of few polygons,
does not require much computer power to manipulate. (Conversely, Mr.
Wanat said, if a game's polygon count is too high, the game could grind
to little more than a slide show without the fluid motion of movies.)
The benefit is two-fold, game designers say. Not
only are game environments and objects vastly more realistic than games
developed even a few years ago, but the reduced amount of processing
power required also allows game resources to be redirected to other
visual effects. That may include smoke and fog or background actions
like the occasional bird flying by or palm trees swaying in a
make-believe tropical breeze.
"Now artists are no longer handcuffed by the
constraints of the machine running the game," Mr. Wanat said. In the
not-so-distant past, he noted, artists often had to narrow their vision
of game worlds and characters. The artist might want a brick wall to be
pitted and mottled, say, but the lack of normal mapping and the low
polygon limit would usually result in a flat geometric pattern of
uniformly smooth, red bricks with no texture to them.
The Riddick game, which is to go on sale in June
shortly before the release of the film "The Chronicles of Riddick,"
makes extensive use of normal mapping. The game, which is set inside a
prison on a barren planet, has a dark, gritty and eerily realistic look.
The ultrarealism was created by using normal mapping
on almost everything, including the Riddick character (played in the
film by Vin Diesel) and even speeding bullets, according to Mr. Wanat
and Jens Matthies, the lead artist on the game, which was jointly
developed with Starbreeze in Sweden.
But normal mapping involves more than simply
displaying minutely detailed game surfaces. By adding additional layers
to low-polygon models of walls, warriors and weapons that are encoded
with specific instructions about reflectivity (called "specular"
information) and color, objects can be made to look even more
realistic, particularly when they move or when other objects pass
before them.
A normal map's specular information tells the game's
core program, called a game engine, how to treat a given surface, Mr.
Matthies said in a telephone interview from his office near Stockholm.
If that object is a pipe, for example, the game engine is told "which
part of it reflects light and which does not shine or how intense the
shine becomes," he said.
The overall result is a video game that comes close
to matching the movie in realism, Mr. Wanat said. "Normal maps," he
added, "get that real-life feel into images."
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