By Karen Moltenbrey
|Creating the visual effects for Helen of Troy was far from horseplay for the CG artists at Stargate Digital. To make a CG version of the famed Trojan horse, for example, they sculpted a physical maquette, built a 3D model from that using Softimage, then a
Her beauty is legendary. And it's said that in 1200 BC, hers was the face that launched a thousand ships and sparked the war between the Trojans and the Greeks. She is the mythical Helen of Troy, the half-mortal daughter of Zeus, born to the lovely queen of Sparta. Many tried to win her love, and many were destroyed in the process. It's unknown whether the story of Helen, or even the woman herself, had any roots in reality, yet her powerful tale has been retold for centuries. Recently, it launched one of this season's biggest television productions: USA Network's epic miniseries Helen of Troy.
Making this project a reality was an epic challenge for director John Kent Harrison. One of the biggest demands was presenting a story that supposedly took place 3000 years ago. "It requires a 3000-year-old setting," remarks Harrison, who strived for the most authentic look possible. To this end, the production crew crafted the weapons, artifacts, and clothing in much the same way artisans did back in this period. Some props, though, required modern methods, including the use of photorealistic computer graphic imagery. Re-creating this time period with CGI fell to Sam Nicholson and his staff at Stargate Digital, an effects house in Pasadena, California, that focuses on what Nicholson terms "the virtual back lot."
"It's where virtual reality meets the reality of filmmaking, with real actors and real sets blended seamlessly with CGI, matte paintings, and 2D compositing so what's real and what's not real become one," explains Nicholson, Stargate's president who also served as visual effects supervisor for the production. "Now there are no limits on what you can do as a director."
This philosophy enabled Harrison to achieve his vision for the production. In Helen of Troy, what couldn't be physically built was created with computer graphics. In fact, digital imagery played a leading role in the production, as nearly 70 percent of the visual effects shots contain 3D imagery. This includes synthetic backgrounds and set extensions, soldiers, weapons, ships, crews, and the famed Trojan horse. "We blended photorealistic 3D imagery with live-action photography to a point where you can't distinguish between them, whether [the CGI] is in the foreground, background, or middle ground," says Nicholson. "We used 3D fluidly on almost every shot. And the shots were big—big battles, big scenery, big everything. Yet the story is not interrupted by the CG; it is enhanced by it."
Nicholson points out that some shots had more than 360 layers of information composited together to achieve the desired realism. Some are entirely CG and last for as long as 30 seconds. Incorporating such a tremendous amount of photorealistic CGI into the scenes required that nearly all the live-action shots be camera tracked for seamless integration. This was accomplished using 2d3's boujou software. "On a big epic like this, you can't tie the director's hands by saying that he can't move the camera," adds Peter Ware, visual effects producer. "He needs to get inside the action."
Known as Helen of Troy, the stunning woman was the stepdaughter of King Tyndareus of Sparta. From an early age, her beauty became a lure that no one could resist. From the moment that Paris, a handsome prince from Troy, sees Helen, he can think of no one else. But Helen is married to King Menelaus (brother of the fierce King Agamemnon of Mycenae, who is wed to Helen's sister). And Paris is facing an almost certain death at the hands of the Spartans, sent by his own father, who had been warned upon Paris's birth that Troy would burn if the boy lives. Hoping to escape their individual but intertwined curses, Helen and Paris flee Sparta and eventually find refuge in Troy. Seizing an opportunity created by this betrayal, King Agamemnon convinces his brother, King Menelaus, and the other Aegean kings to attack Troy, whose riches Agamemnon has always coveted.
|To rebuild Athens and other cities as they may have existed 3000 years ago, Stargate artists generated digital matte paintings and CG set extensions.
Thus ensues ancient civilization's greatest war, which raged for 10 years around the walls of the beautiful city of Troy, according to mythology, nearly destroying the two most powerful nations of the time—Greece and Troy. The war finally ends when the Greeks overtake Troy after hiding inside the hollowed interior of a huge wooden horse, presented as a gift to the unsuspecting enemy.
Nearly 95 percent of this $14 million production was shot in Malta, which served as the setting for Athens, Sparta, Mycenae, and Troy. Constructing sets large enough to convey the richness and the enormity of the ancient empires was far beyond the scope and budget of the production crews. To augment the physical setting, the artists at Stargate generated digital matte-painted backgrounds and elaborate CG set extensions that set the stage for this epic event.
A team of three artists, lead by Stargate's art director Tim Donahue, worked continuously through the project to create the 70 2D and 3D matte paintings that depict the cities of Athens, Troy, and Sparta, and nearly every location in between. Using Adobe Systems' Photoshop, the group generated complex 3D multiplane layers and digital paintings that were projection-mapped onto 3D models. "The mattes also kept us focused geographically, especially during the battle sequences," says Ware. In other instances, the group created photorealistic extensions—nearly every shot depicting the city of Troy contained a CG set extension—that blended seamlessly with partially built physical sets. Sparta, on the other hand, was mainly a practical set with the exception of shots outside the city walls and those above a certain level. To ensure an exact union between the real and the digital, Nicholson and his assistant, Matthew Pullicino, took more than 5000 digital photographs of Malta, which were then used as textures for the CG elements.
One of the more impressive scenes in the movie is a 20-minute sequence showing the invasion of Troy. "Epic battles scenes like those in Braveheart and Gladiator have sharpened an audience's awareness and expectations for realism, and Helen of Troy would have to at least match that intensity in every aspect, despite its much lower budget," says Harrison.
Harrison used detailed storyboards to choreograph the battle, lest it turn into total chaos. Then, Nicholson turned the small group of 300 extras into a spirited army of 10,000 Greek and Trojan warriors. First, the Stargate group conducted full 3D studies of the extras, photographing their faces from all angles in high resolution. The artists then blended that information into texture maps and wrapped them around the character models, which were generated in Alias|Wavefront's Maya, to ensure that the digital doubles blended into the scenes with the live actors.
|Stargate used matte-painted backgrounds to help provide a geographic focus for the massive battle sequences that occurred throughout the miniseries.
"We also spent a few days photographing every piece of wardrobe against greenscreen so we could construct an exact duplicate of whatever we had on set," Nicholson says. This included the costumes, jewelry, and other materials that were meticulously crafted to match those that had been unearthed from archaeological expeditions.
Rather than using crowd-simulation software, the team instead keyframed most of the models in Maya. For some of the battle scenes, though, the group used its own dynamics system to provide the characters with basic rules. For instance, a synthetic actor would fall a certain way depending on where he was struck by a 3D arrow; if he raised his shield, the arrow would strike that instead. In fact, all the arrows used in the movie were 3D, as "the Maltise [extras] were not very good at shooting arrows," notes Ware.
|The artists used 3D models and digitally cloned extras to turn a group of a hundred or so (tob) into an army of thousands (above).
In addition to the 3D actors, the group also cloned many of the extras by rotoscoping them from footage shot against greenscreen. Nicholson also created numerous groups, or "pods," of soldiers using a traditional multipass camera duplication method while filming the live-action battle scenes. Later, these groups and clones were composited into the final scene using Adobe's After Effects, many of them in the middle ground and foreground, resulting in a seamless blend of real actors and synthetic soldiers. In all, Nicholson estimates that approximately two-thirds of the digital soldiers were clones and pods; the other third were 3D models.
Replicating digital people was one challenge, but replicating Mother Nature presented yet another. For a scene in which Paris and Helen flee Sparta by ship, the team had to conjure up a massive storm. To simulate this action, the production crew used Malta's water-effects tank, a four-acre enclosed section of ocean that aligns with the horizon. The digital artists helped augment this and other aquatic shots using Maya.
Another key sequence in the movie contains the fleet of boats launched by the Greeks against Troy. For this, the producer needed 1000 ships, including their crews. First, the production teams constructed a full-scale boat that served as a reference for the digital models. Next, Stargate's CGI supervisor Josh Hatton and the CG team began building detailed 3D ship models in Maya, to which they added the textures acquired from the real boat, different types of sails, and dynamic rigging to vary each boat's appearance. Stargate's CGI group then wrote custom code for the sails, rigging, and oar dynamics, which enabled the entire Greek fleet to set sail and react individually to the wind and water forces on a digital ocean.
|Most scenes in the movie blend live action with computer graphics, but this shot depicting the launch of "1000 ships" is entirely CG.
According to Ware, the Maltise actors not only had a difficult time with archery, but also rowing. Therefore, the oar props and the soldiers themselves were digitally replaced, which required the artists to generate the proper water dynamics as the 3D oars dipped into the water. "A scene like that is compute-intensive just for one boat, but we had to multiply it by 1000, and add a camera pan of a CG city of Troy in the background," he notes.
The digital centerpiece of the production is the fabled Trojan horse, which makes a grand entrance in the miniseries. Nicholson designed and directed this sequence in order to maximize the blocking, or staging, of the live-action scenes, which would later be combined with the photoreal CGI. He also integrated dramatic camera moves for approximately 15 shots of the horse as it is towed inside the gates of Troy.
|To minimize postproduction work, the movie's visual effects supervisor directed the live-action sequence involving the 3D Trojan horse.
The horse, an all-3D model built in Softimage, "is stunning and fully raytraced," comments Nicholson. The object was crafted to look as if it had been constructed with materials at the soldiers' disposal—wood, oars, planks, armor, and shields. Aside from the ships, this was the group's most challenging sequence, notes Nicholson, mainly because of the horse's size and the fact that it is positioned in the foreground.
Prior to modeling the object, production designers first constructed a maquette, which the 3D artists used as a reference while crafting the digital version. "You start off thinking about a 35-foot horse, and then it gets much bigger," says Ware, who estimates the final synthetic version to be about 75 feet. In fact, the scenes were redesigned to accommodate the larger structure, which proved to be the right decision, Ware contends, because the horse is—and should be—an awesome sight. On set, Nicholson used a large forklift as a stand-in for the CG horse to ensure that the actors exerted the proper amount of push, pull, and strain.
Once the Stargate artists built and textured the models, they rendered them in high definition using After Effects running on 100 custom-built PC NT-based workstations. Then, compositing supervisor Adam Ealovega led the After Effects artists, who seamlessly blended hundreds of complex multi-layered, motion-matched shots. In the end, Stargate delivered its film-quality effects on a budget and demanding time schedule required in broadcast—two weeks for prep, 12 weeks for shooting, and another 12 weeks for postproduction. "In television, we are competing with features for the same audience," says Ware. "The challenge in television is to reach that bar with far less money and time. Now, at least, the enabling tools are available at reasonable prices to help us achieve that."
Unlike most studios, whose work is complete once the shots are assembled, Stargate also edited the entire four-hour miniseries using an Avid|DS HD, with effects editor Victor Scalise carrying the project from the director's cut through the final delivery of the on-air master. "For three months we had the entire show uncompressed in high def on our system so we could seamlessly integrate the visual effects," says Nicholson. "We wanted to ensure that the visual effects were not left out in the cold, delivered blind, but integrated as part of the overall online edit from beginning to end. We regard this entire project as a single, digitally enhanced visual effect," a philosophy Stargate has followed while providing virtual backdrops and effects for many prime-time hits, including ER, CSI, and Crossing Jordan.
In Helen of Troy, Stargate succeeded in suspending viewers' disbelief by bringing a mythical figure to life. But is any portion of Helen's story based on fact? Until the 19th century, it was widely believed that Troy and the Trojan War were imaginary, a myth perpetuated by the Roman writer Virgil in the Aeneid, and the Greek poet Homer in the Iliad and Odyssey. But in the late 1800s, an archaeologist—using clues from Homer's writings—discovered what appears to be the lost city of Troy in Turkey. Now, few dispute that Troy and its siege, as described by Homer, was real. Yet there is no evidence supporting Helen's existence. For now, and maybe forever, the truth about her remains a secret of the past.
Karen Moltenbrey is a senior editor of Computer Graphics World.