Blue Sky Studios' fully-CG xenomorph adds new menace to infamous alien.

Designed by Swiss surrealist artist H.R. Giger, the alien with its vertebrated tail, stove-piped back and slimy penile head is one of modern cinema's most recognized monstrosities. Despite its humble man-in-a-suit origins, the alien is one of the most detailed extraterrestrials ever designed a fun factoid, unless of course you're trying to model the creature via computer graphics. On Alien Resurrection, that unenviable task fell to Blue Sky Studios, a New York-based effects house best known for a series of award-winning commercials and for creating hordes of cavorting cockroaches for the MTV film Joe's Apartment.

"Giger's inspirational art is incredibly detailed and rich," says Mitch Kopelman, Blue Sky's digital effects supervisor for Alien Resurrection. "Just modeling the alien took several months. Amalgamated Dynamics Inc. [ADI], which made the suit for both Alien3 and Alien Resurrection, sent us a 1:1 scale alien sculpture, which we cyberscanned. We brought that 3-D reference into Softimage and did a quickie cleanup so we could work with it; that gave us the rough dimensions and proportions of the alien pieces. Then Alex Levenson and Mike DeFeo blew away the cyberscan and modeled all of the details in Alias. We brought those individual pieces into Softimage, where we actually put the alien together attaching the arms to the torso and so on using what we call Animate Connections. We've written a lot of plug-ins to help make the socking of the joints and connections seamless, so when the animator moves the arms or legs, it's got a nice, realistic feel to it."

By using NURB (non-uniform rational B-spline component) data instead of polygons to create their CG model, Blue Sky was able to create a much more dexterous alien. "If we had used traditional polygonal-type models, the alien would have required millions and millions of vertices," Kopelman explains. "That would have made the model incredibly heavy and difficult to animate and render. Fortunately, our homebred renderer, CGI Studio, enabled us to work with the alien model in its NURB state, which reduced the amount of data going into a scene while allowing us to increase the amount of detail in the model. When we finally rendered our CG images, CGI Studio left things in their natural NURB state, so [the computer] didn't have to keep track of all the tons of data."

This was a true boon to the design process, since the alien's facial geometry became ever more complicated as the design evolved throughout preproduction. "Although its head is mostly a big piece of geometry on top, the rigging and modeling of the lips, which had to pull back in stages like separate shades from the teeth, was tricky," admits Christopher Scollard, Blue Sky's visual effects producer. "The most challenging thing about modeling the head was creating the sinewy geometry on the sides that connects the upper and lower jaws."

That element of musculature was crucial since Blue Sky's CG alien wasn't going to be visible merely in long shots. "Our model had to take as large a close-up as the man-in-the-suit version, so we built it with that intention," Kopelman says. "Originally, we planned to build lower-res versions for shots further away, but when we realized we were getting reasonable render times with the high-res model, we stuck with that. Then we painted the texture maps using a combination of Photoshop, Amazon and some of our own projection tools."

Matching the textures of the CG alien to those of the original suit was a constant challenge, because the suit suffered wear-and-tear throughout principal photography. "Re-creating the material properties of the alien's skin was also difficult," Kopelman adds. "The suit was coated with goo, and that greasy quality was difficult to simulate in computer graphics. A nice, clean plastic highlight is what we can do most easily, and this was anything but. There's a lot of organic complexity to the alien, so there are a lot of texture maps on that baby upwards of 150-200 megabytes to help it along."

The texture maps, coupled with some complex animation rigging developed by Blue Sky animators Jim Bresnahan and Steve Talkowski, paid off in brutal close-ups of the alien's anatomy. One example is the Jurassic Park-inspired tight shot of the alien's foot landing in frame, followed by a shot in which the alien steps over camera and heads down a hallway, swishing its tail in the lens. "We spent a lot of time coming up with animation rigs that would simulate the musculature and tendons of those legs," Kopelman says. "As the foot lands on the floor in close-up, the toes spread, the mass settles out, and the calf muscle tightens. The animation rig was just as complicated as our initial geometric alien model, so some of that stuff was partially automated. Even so, the animation of the big foot landing, followed by the alien taking three more steps down the corridor, took a couple of weeks."

This explanation raises a question: why make the CG alien walk at all when there was a perfectly mobile man-in-a-suit version? "We thought we'd be doing all of this crazy action," Scollard says with a grin. "We didn't realize that nobody's ever seen the alien walk upright. The alien has tri-segmented legs like dogs' legs and a guy-in-a-suit can't walk like that if you want to see the legs in frame. That was a tremendous back-and-forth expedition."

Blue Sky's 50-person team researched alien ambulation by videotaping Tom Woodruff of ADI walking in the suit, which featured conventional humanoid two-jointed legs instead of the CG character's three-jointed dinosaur/ostrich-type limbs. Kopelman says, "We hoped to get the attitude of the alien's legs and upper body, and the pace of its movements, from the videotape, but its actions looked too human because it was a human. So we tried to go as far away as possible from a human with our animated walk."

The challenge for Blue Sky's animation team, which was led by Jan Carle'e, was to create a bipedal walk using tri-segmented legs which didn't look human but also weren't clumsy. "There are a limited number of ways a biped can walk and still be believable," Scollard maintains. "Our solution sounds contradictory, but the alien moves like a sort of vulnerable predator. He reduces his size and looks very protective, but he really has no fear. It's just a way for a giant creature to minimize his space. He walks at a diagonal, which I think is predatorially efficient."

Kopelman adds, "The director, Jean-Pierre Jeunet, had this vision of the alien having a very deliberate, 'I'm-gonna-get-you' gait, kind of like a gunslinger's, with a real slow, in-charge attitude. It's like John Wayne or Clint Eastwood very purposeful. We could accomplish those slow movements because our CG model was so detailed. The tail has a nice, whippy motion and a dagger-like feel, but the head moves very slowly. The alien's motions are really graceful, very purposeful and fearless; it was very interesting to animate."

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