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| Fasten your seatbelts: Peter Jackson's second Lord of the Rings installment will feature one of the most spectacular battle scenes in film history, a product of the digital dark arts. by Dan Koeppel |
Posted on 11/29/2002 1:18:03 PM PST by JameRetief
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| Fasten your seatbelts: Peter Jackson's second Lord of the Rings installment will feature one of the most spectacular battle scenes in film history, a product of the digital dark arts. by Dan Koeppel |
 AGENTS OF DESTRUCTION: Thousands of digitally created fighters clash with humanity in the Battle of Helm’s Deep, top. Bottom: A Massive agent uncloaked. |
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IN DECEMBER VAST HORDES OF EAGER FILMGOERS will mob cineplexes across the land and witness, at the climax of The Two Towers, one of the most anticipated scenes in recent movie history: the great Battle of Helm's Deep. The Two Towers is the second film in Peter Jackson's audacious and, so far, triumphant Lord of the Rings trilogy. In this installment, the action takes a darker turn: Humanity and its ragtag allies engage the monstrous forces that would dominate Middle Earth. Humans, hobbits, wizards, dwarves and elves are called to arms against Orcs, Ringwraiths and their awful legion of followers—something like 50,000 fighters on the ground, all but the relatively small number of main characters computer-generated. The battle ebbs and flows across the foot of a great mountain range. Lightning flashes and rain pounds the nighttime spectacle. Fighters skirmish up and down the long ladders that line fortress walls.
The battle represents a milestone in computer-generated filmmaking. Combat scenes are one of the big challenges of the digital arts, so complicated is the mix of chaos and purposeful action that plays out when soldiers clash in large numbers. Swell the number to thousands and make each fighter appear autonomous onscreen: That was the gauntlet Jackson threw down to his programmers, and if they have pulled it off this will be the most spectacular CG scene ever. Needless to say, new technology was required.
"Our perception of characters is very sharp, which makes it all the more difficult to get the subtle details of artificial life forms believable," says Karl Sims, a former MIT researcher whose 1994 paper, "Evolving Virtual Creatures," outlined the key challenge that digital animators grapple with. Human (and humanoid) forms represent the highest order of CG simulation because audiences are trained since birth to track human movement in all its complexity. So far, Sims says, filmmakers have done better with smaller creatures: "Even swarms of insects are easier to simulate than humans."
Until recently, relatively simple simulations of physical interactions have driven digital crowd sequences. Using basic rules governing attraction and repulsion, designers aimed single points called particles at each other. Each particle represents a different individual, and when a satisfactory mix is achieved to portray the movements of a group or crowd, animation is added: The particle is rendered as a digital human or creature. The result is cost-effective but not always natural-looking; particle trajectories emulate pool-table-level physics across a two-dimensional space. The movement of real people, especially in battle over rough terrain, is a hugely more complex challenge for the programmer.
Peter Jackson, shooting his films in the unlikely, un-Hollywood setting of New Zealand, favored a different approach. Jackson had already shown his maverick style in his effects-rich 1996 poltergeist film, The Frighteners. For the film's effects, he employed WETA, a sort of Kiwi upstart version of George Lucas's Industrial Light and Magic that Jackson began in 1993. In 1996, he asked fellow New Zealander Stephen Regelous, who'd worked as a technical director on The Frighteners, to become the crowds supervisor (a digital wrangler in the service of Jackson's Cecil B. DeMille vision) for The Fellowship of the Ring, the film that launched the trilogy. Regelous had long been unhappy with particle-based products, and he wanted to start from scratch. Influenced by artificial life theorists like MIT's Sims, and a student of medieval battles, Regelous spent the next several years writing Massive, a software program that generates crowds whose interaction is based not on particle dynamics but on unique and unpredictable choices made by individual characters within a scene. Rather than concentrating on duplicating mechanical actions, Massive endows each character with a digital brain and gives it the power to act completely on its own. In an AI sense, the characters fighting in Helm's Deep are, well, fighting.
This approach means much less reliance on cutting and pasting (the initially impressive Colosseum crowd in Gladiator was made by duplicating and digitally tweaking 200 human extras; viewed carefully, the carbon copy spectators can create a disconcerting effect). Massive was built on the understanding that the believability of a cast of thousands depends on the actions of individuals. "If (one Orc) acts naturally," Regelous says, "so will the group."
When Orc meets elf in digital battle, neither knows exactly what he—or his opponent—is going to do. The elf may swing his sword, but when? His opponent will see it and duck (or not, and not). The elf jumps forward. The Orc cowers—and this time, the elf's blow finds bone. While the result of the whole battle is broadly predetermined—there is a plot—individual sequences have what might be called programmed spontaneity. Each movement emerges from the one before it.
Massive characters, or "agents," function as complex beings subject to physical forces, with specific body attributes that range from the biological (short, good eyesight, dark skin) to the behavioral (aggressive). These features govern a Massive character's ability to generate credible motion. Each character is assigned a host of potential actions, as many as 350, each about a second long (sword up, sword down, step forward, step back). How these actions play out is determined by the character's brain, a tangled web of anywhere from 100 to 8,000 behavioral logic nodes, which provide the rules that allow each character to perceive, interpret and respond to what's happening around it: to make decisions and act. These nodes group into rule collections which control aggression, fighting style, movement across varied terrain, and a dozen other factors. Regelous originally tried to use pen and paper to sketch the relationships between nodes in a character. "It got chaotic very fast," he says, and Massive designers now use a special graphical user interface to connect nodes and create an agent's brain. A fully formed character—a map of its tendencies, its personality, if you will—looks like a huge, multidimensional spider web on the screen.
 CREATING EVIL: In The Two Towers, the evil wizard Saruman breeds legions of fearsome Uruk-Hai fighters, seen above leaving the Orthanc Tower on the way to Helm's Deep. But it takes fuzzy logic and artificial intelligence, not magic, to make the soldiers come to life on screen. |
Once created, Massive characters are inserted into unpopulated scenes. The characters are then left to do what they've been created to do, and a battle scene assembles itself. This can take minutes, or overnight, depending on the size and complexity of the scene. Beyond general tendencies, the filmmaker does not know precisely what a character will do, since each is an autonomous and, within the confines of the digital landscape, sentient being. Regelous' laptop still contains an early sequence in which a pair of fighters—an Orc and a human—began a strange dance borne of too-finely balanced combat and obstacle avoidance modules. The digital opponents approach, circle and brandish weapons, but never clash. In another early simulation, Jackson and Regelous watched as several thousand characters fought like hell while, in the background, a small contingent of combatants seemed to think better of it and run away. They weren't programmed to do this. It just happened. "It was spooky," Jackson said in an interview last year.
To avoid surprises, Massive programmers weeded out ineffective agents and duplicated ones that worked. About a dozen initial master characters formed the basic genetic blueprint for more than 50,000 digital creations, which were then individualized by adding random variables such as aggression or happiness. (A few update Tolkien; keep an eye out for a background character in The Two Towers who, in the middle of the battle, seems to take a call on his cellphone.)
Despite fuzzy logic and complex node webs, these characters have less brainpower than ants, and the whole battle is a foregone conclusion. The winning team is endowed from the start with the digital DNA needed for victory. Scenes are broken into easier-to-control smaller components, and agents are chosen whose tendencies will draw them into proper continuity. As the software has matured, the movie's technical directors have learned how to tweak agents on the fly, honing movements and responses so that minor flaws in already rendered sequences can be touched up.
In the movie, the Orc army stands before the fortress, pounding spears into the ground. Rain falls, and the darkness is broken only by flashes of lightning reflecting off helmets. The battle begins, and sprawls across the screen until—when all seems lost—an unexpected . . . no, we're not telling. If Massive has worked its magic well, the story will sweep viewers away and most won't stop to single out the software's more realistic touches. But watch the Orcs climbing ladders: Complex physical movements are a tough trick for point-based digital characters, much easier for Massive creations. "You're going to see hundreds and hundreds of very detailed things like that," Regelous promises. In particle-driven effects, characters rarely walk on rough terrain because it looks awkward. Massive agents are more nimble. (On his laptop, Regelous modifies the landscape as a character moves across it, and the computer-generated stick figure ducks and weaves without hesitation.)
Regelous is hoping the next version of Massive, which he's now showing to U.S. movie studios, will be even more powerful, containing components that allow characters to evolve. In the meantime, other developers are building sophisticated decision-making capabilities into their own digital characters. The arena sequence in the most recent Star Wars installment, for example, used artificial intelligence to create individual actions for 30,000 particle-based characters, to good effect; expect further improvements in Episode III. In Return of the King, the final film in the Lord of the Rings trilogy, the climactic battle—yes, the Battle of Helm's Deep is just a run-up—is rumored to employ more than 100,000 characters.
What audiences will see on December 18 marks another step on the road to creating digital characters that feel so real that viewers can't tell them from their flesh-and-blood Hollywood co-actors, a journey that started two decades ago with Tron. "Right now," says artificial life pioneer Karl Sims, "you can still usually tell when something is synthetic. But we'll soon be crossing over into a time where that's not possible. It's going to be a very interesting moment."
Dan Koeppel, a film-school dropout, has written for Wired and The New York Times Magazine. Although a longtime Tolkien reader, he draws the line at The Silmarillion.
Uh...I couldn't make it through the movie, though...I'm series.
I am taking Dec. 18th off from work to see The Two Towers a couple of times.
Let's hunt some Orc!
 Ring Ping!! |
LOL! Why am I not surprised by this? I love Jackie Chan, a true master.
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Some neat info about the effects in here.
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