Issue: Volume: 26 Issue: 7 (July 2003)

CG Superheroes: X-cellent FX


By Barbara Robertson

Opening to a record-breaking box office of $155 million internationally in its first weekend, 20th Century Fox's X2: X-Men United gave the summer movie season a welcome kick-start.

With the audience having already met the cast, director Bryan Singer took the opportunity to concentrate on the characters' abilities and relationships in this sequel. Still, X2 is a more classic translation of comic book to film than The Hulk. It's an exaggeration, but not a huge one, to think of the effects in The Hulk as happening to the main character, himself an effect, causing him to think and feel and act in particular ways. On the other hand, the effects shots in X2—all 850 or so of them—are driven by an ensemble cast of superheroes (who are not, for the most part, effects themselves).

















Four different studios worked on these X-Men effects. From top to bottom: Colossus's metal body, Rhythm & Hues; Mystique's scales and transformation, Kleiser-Walczak; Mystique's eyes, CIS; Storm's storms, Rhythm & Hues; Wolverine's cla




These X-Men (and women, it should be noted) are mutants, outcasts feared and loathed by humans unable to accept their differences. As the next link in the evolutionary chain, each has a unique genetic mutation that gives him or her an extraordinary power—and the filmmakers a reason for visual effects. "The effects are integral to the characters," says Mike Fink, visual effects supervisor. "They are all about the characters." Some CG effects enhance or change the mutants' bodies: the blue scales and shape shifting of Mystique (Rebecca Romijn-Stamos), the retractable claws of both Wolverine (Hugh Jackman) and Deathstrike (Kelly Hu), Nightcrawler's (Alan Cumming) tail, and several mutant eyes. Other effects show mutant power: Storm (Halle Berry) makes weather. Pyro (John Allerdyce) throws fire. Iceman (Shawn Ashmore) freezes whatever he wants. Cyclops (James Marsden) sends energy beams. Nightcrawler teleports.

Three studios—Cinesite, Kleiser-Walczak, and Rhythm & Hues—had a lion's share of the work. Cinesite and Kleiser-Walczak created two of the most extreme mutant effects: the Nightcrawler's teleportations and Mystique's transformations. Rhythm & Hues handled two of the most dramatic effects sequences: a dogfight and a scene near the end in which Jean Gray (Famke Janssen) controls a wall of water.

Nightcrawler provides the film's dramatic opening—an attack in the White House by a fast-moving, acrobatic, martial-arts maneuvering, blue-faced intruder. Each time the Secret Service takes aim, the intruder vanishes in a cloud of smoke. "It sets the tone for the movie, that it's bigger and badder than before," says Gregory Anderson, CG supervisor at Cinesite. "From the beginning, because Nightcrawler is a fast, agile character, we wanted to have a teleportation effect that reflected that, but the last thing we wanted was a cartoonish poof in which one frame he's there and the next frame he's gone." Instead, smoke trails off Nightcrawler as he dematerializes and a rush of smoke fills the void.

To create the effect, the Cinesite team started with a rough model of actor Alan Cummings that was fashioned using Alias|.Wavefront's Maya in six sections: head, torso, arms, and legs. Then, in Side Effects Software's Houdini, the crew filled the virtual volumes with particles that were rendered in Side Effects' Mantra using a smoke shader and Houdini's i3D volume rendering datasets. With the body in sections, the artists could control each volume to make him dematerialize all at once or have an arm or a leg lag behind. To make the smoke disappear, they pulled particles in the volumes inward and rendered the implosion with Maya.

The streaming smoke and the residual smoke were also created with particles and were animated with a fluid dynamic algorithm written by Jerry Tessendorf that was ported into Houdini as a particle operator and used as a turbulence field. To render a nearly impossible number of these particles—sometimes as many as 20 million—they used a proprietary tool called PartMan, written by Tessendorf and Bill LaBarge, 3D technical director. "We could render six million particles using 125mb of RAM and a general pass in 15 to 30 minutes per frame at high resolution," says Anderson. "This meant we could render the effects in multiple layers and recombine them in the comp." The compositing was done with Kodak's Cineon software.

To fasten the smoke to the live-action Nightcrawler, the compositing crew matched-moved the rendered output into a relative position, rotoscoped Nightcrawler, and then replaced his alpha with the render's alpha. "On top of that we did a series of 2D distortion effects," Anderson says. "As he implodes, we gave it a slight expansion outward before the effect and then collapsed it inward."

Last, the crew attached a CG tail to Nightcrawler for scenes in which he's moving fast; otherwise, the tail was a prosthesis. In addition to Nightcrawler, Cinesite also created Pyro's fire, the frost Iceman uses to freeze whatever (or whomever) he chooses, Cyclops's white "energy" beam, the atmospheric Cerebro with its ethereal floating images of the mutants, and a fiery "Phoenix effect" around Jean Gray at the end of the film. "This is a particle show," says Fink. "Some of Pyro's fire is practical, but when the fire is CG, it's made of particles. The frost is all volumetric rendering, and the Cyclops beam is a particle effect, too, that used PartMan for rendering. Also, because PartMan would render hundreds of particles so that they looked like millions without creating clumps, it gave Cerebro a true vaporous/gaseous look that didn't look mathematically computed."













To create Nightcrawler's "bamf," that is, a smoky teleportation effect, the crew at Cinesite used a Maya model, Houdini particles, Mantra to render the implosion, Cinesite's PartMan to render the residual smoke, and Cineon for compositing. His tai




The exception to the particle rule was Mystique. As for the first film, Kleiser-Walczak handled her scales and her transformations. "I think we raised the bar across the board," says Frank Vitz. "We used more accurate scans, a more detailed model, high dynamic range imaging to get a global illumination look, and ambient occlusion shadows. We also had more subtle choreographic control of her transformations. But the idea was to look consistent—make it better than the first X-Men film, but not change anything."

Mystique's scales, each made of polygons with textures and displacement maps, had animation cycles so they could extrude, fold over, flutter, and lie down. "As a transformation passes through her body, scales could be triggered individually, in groups, or they could all move together," Vitz says. "We wanted to control the transformation and have it move like a wave over her body."

Using Maya plug-ins written by Daniel Roizman of Kolektiv, the team could make the transformation happen fast, or slow and sensuously, as they did for a scene in which Mystique attempts to seduce Wolverine by transforming into one beautiful woman after another. Using texture maps projected onto 3D models within Maya, the team would blend from one digital double to another. "We generated complex 3D texture ramps to manage the effect," Vitz explains. "The ramps controlled all the attributes, including morph progress, skin shaders, scales, the works. By adjusting the ramp timings, we could easily choreograph which part of her body transformed and when." To help make the 3D morph look as if the shape change happened deeply, not just on the surface, they gave the leading edge a variegated quality and added highlights and shadows based on displacement.

Meanwhile, Rhythm & Hues was working on several effects including the fight in the "augmentation room" between Deathstrike and Wolverine, who share the same mutations—retractable claws and nearly instant healing. For shots in which real claws would be dangerous, 3D claws were added to their hands using Rhythm & Hues's proprietary tracking, lighting, and rendering software. To heal cuts on the mutants' faces, the augmentation team used Avid's Elastic Reality to morph between cut and clean faces. "We closed the wounds like a zipper," says sequence lead Sean McPherson. When Wolverine kills Deathstrike by throwing her into a vat of liquid metal, adamantium metal tears flow down her cheeks thanks to Houdini metaballs traveling down splines.

"We used Houdini for a lot of our effects shots," says Richard Hollander, visual effects supervisor at Rhythm & Hues. "Like most shops, we pick from a potpourri of tools." But, he says, the studio's pipeline includes the studio's Voodoo for animation, its Wren for rendering, Side Effects' Mantra, 2d3's boujou, Science-D-Visions' 3D Equalizer, Apple's Shake and Rayz, and Discreet's inferno series. They also use Maya for modeling, Elastic Reality for morphing, and Steamboat Software's Jig for volumetric rendering, he adds.









Changing Mystique into her blue scaly self was again accomplished by Kleiser-Walczak, this time with more subtle control of the transformations and more sophisticated lighting effects than for the first X-Men film.




At one time, Rhythm & Hues had 200 people working on X2 shots, such as those at the end of the film where our superheroes fly their X-jet toward the dam at Alkali Flats to rescue Cyclops and Professor Xavier (Patrick Stewart). During a dogfight on the way, the interior of the X-jet behind the actors, the exterior of the X-jet, and the exteriors of the military jets pursuing the mutants are all CG. To give the mutants an edge in the fight, Storm creates a sky filled with tornadoes—yet another volumetric particle simulation.

In addition to claws, jets, and tornadoes, Rhythm & Hues also crafted water. "The wall of water, the water rushing by, the water that separates around an X-jet, are all CG water," says Hollander. To create it, the crew used a Martian Labs water simulator that added shading and displacement maps to surface geometry created in Houdini; water beneath the surface was created with Houdini particles rendered with Steamboat's Jig. "Each particle was a sphere with noise inside it, and that noise became the veins of the water, so to speak," says lead effects animator Mike O'Neil. "It's also how we did tornadoes. We animated particles with large spheres to have control, filled the spheres with noise, and rendered them with Jig.

At the end of the film, when Jean Gray is holding back the water in the dam, she's engulfed with a fiery energy, an effect created at Cinesite. Arnon Manor, CG supervisor, explains that a model with a CG skeleton was animated to match Janssen's movements. That model acted both as a particle emitter and as a collision object. "We wanted it to look like fire was coming off and wrapping around her," he says. They rendered the effect into numerous layers using Maya's renderer, integrated it with mist elements created in Houdini, and composited the layers in Cineon.

In addition to the dogfight, tornado, and water sequences, Rhythm & Hues handled the plastic prison escape, shots of Colossus turning into metal, and a storm outside the White House.

"A few other studios worked on the show as well," says Fink. "Visual Concepts Engineering enhanced miniatures, CIS replaced Rebecca's (Mystique's) eyes, and Pacific Title did probably 100 miscellaneous shots." In addition, Frantic Films, which created much of the film's previsualization using Discreet's 3ds max, also contributed hologram effects, and Asylum handled the title sequence.

Remarkably, these studios accomplished nearly all this work in a 17-week postproduction period. "Richard [Hollander] and I have been friends for 25 years, and neither of us could remember anything as brutal as this schedule," says Fink. "We worked seven days a week."

What this suggests is that the real superheroes were not the characters in the film, but the people in the effects studios who pulled it all together.

Barbara Robertson, contributing editor of Computer Graphics World and a freelance journalist, can be reached at barbaraRR@attbi.com.




2d3 www.2d3.com
Apple Computer www.apple.com
Alias|Wavefront www.aliaswavefront.com
Avid www.avid.com
Discreet www.discreet.com
Kodak www.kodak.com
Martian Labs www.martian-labs.com
Science-D-Visions www.sci-d-vis.com
Side Effects Software www.sidefx.com
Steamboat Software www.steamboat-software.com
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