Issue: Volume: 29 Issue: 7 (July 2006)

Leaps Tall Orders


By Barbara Robertson
Sony Pictures Imageworks creates a digital Superman for close encounters
 
When Superman soared above Lois Lane’s house in Warner Bros’ Superman Returns, he flew on the wings of computer graphics technology and visual effects expertise that has taken superheroes and digital humans to new heights.
 
Andy Jones, animation supervisor at Sony Pictures Image works and Oscar nominee for I, Robot, led the team that created the digital stunt double’s performance. Richard Hoover, Oscar nominee for Armageddon, supervised Image works’ 300 visual effects shots. Mark Stetson, who won a visual effects Oscar for The Lord of the Rings: The Fellowship of the Ring, supervised the work of 11 visual effects studios that created the film’s 1400 shots. And, Bryan Singer of X-Men and X-Men 2 fame directed the film.
 
 
Digital stunt doubles have accelerated the actions of superheroes since Batman took a 60-foot tumble in 1995’s Batman Forever, and with each, the camera has moved closer to the digital double’s face. “We got much closer than we ever thought we’d be,” says Jones of Superman. “In one shot in particular, his head is about a third, maybe half, the screen space. There were only a few shots like that, but they were extremely challenging.”
 
Jones should know. As animation director for Final Fantasy: The Spirits Within and I, Robot, digital stunt sequence supervisor for Titanic, and director of The Animatrix and Final Flight of the Osiris, he’s spent much of his career leading teams that have put photorealistic (and stylized) digital humans on screen. “The techniques for face shots have changed quite a bit from Final Fantasy,” he says, “and also what we can do with animation, skin dynamics, and muscles.”
 

In some shots, Superman is actor Brandon Routh “flying” on wires against a greenscreen
with puppeteers maneuvering his cape, as shown in the photograph above.
Compositors then blended the greenscreen footage into background plates and digital
environments.
 
To reproduce the face of Brandon Routh, who plays the role of the Man of Steel, Image works used the same Light Stage 2 system developed by Paul Debevec and his team at USC’s Institute for Creative Technology that had captured Alfred Molino’s face to create Doc Ock in Spider- Man 2. With the Light Stage 2 system, an actor sits unmoving in a chair while a mechanical arm fastened with strobe lights swings around the chair. The lights strobe, the arm moves, and cameras positioned around the chair photograph the actor’s face to produce images in various lighting conditions.
 
For Spider-Man 2, Image works used four synchronized cameras, but later discovered they had missed part of Molino’s neck. For Superman Returns, they captured Routh’s face and the back of his head using six ARRI Group Arriflex film cameras snapping images at the rate of 60 frames per second. At the end of the session, Image works had 480 sets of six images. Each set of images, when blended, could surround a 3D model of Routh’s head with a seamless photo of his face. Some image sets captured specific expressions—eyes open, eyes closed, and mouth open, mouth closed, for example; others captured a neutral expression.
 

However, Superman is often Routh’s digital double created at Sony Pictures Imageworks, as in the
image here.
 
“We have several shots where the digital Superman flies right by the lens, and we get a really good look at his face,” says Hoover. “We get close enough to see his expression.”
 
A technical crew led by John Monos removed highlights from the images, used custom algorithms to extract reflective data, and ended up with 480 reflectance maps that could wrap like a rubber sheet around the 3D model of the actor’s head and on which technical directors could aim CG lights. “Our TDs just position lights, and based on that, the map comes in,” explains Monos. A custom algorithm helped the TDs dial in reflectance data as the face moved, and the image-based rendering (IBR) system handled potential problems with double shadows.
 
“With IBR, shadows are baked in, like the shadows from the nose onto the cheek,” Monos says. “We didn’t want a double shadow if maybe an arm crossed the faces, so we resolved that internally as part of the program.” Although the crew captured Routh’s hands with the Light Stage 2 system, his hands moved so much that it became easier to use painted texture maps and traditional rendering with subsurface scattering.
 
Faster than a Speeding Bullet
To create Superman’s performance, animators worked with motion-capture data and green screen reference. They captured Routh in basic flying poses and, because the crew thought it would need to have the digital double deliver dialog, it motion-captured facial expressions based on Image works’ proprietary application of the Facial Action Coding System, also used in Monster House (see “This Old House,” pg. 28). “It was extremely challenging trying to make a superhero look real and still look like a superhero,” says Jones. “The instinct is to go for comic book poses and fun, big styles of motion. But Bryan [Singer] wanted us to pull back and make him look real, with a cool factor.”
 
The flying shots were a mixture of all digital double, all green screen images of Routh on wires, and Routh’s head on a digital body. “We had close-up shots where they couldn’t use his face for one reason or another, so we had to get the essence of Brandon [Routh] in there,” says Jones. Some were especially demanding. “In a few, we went from the CG human into a live-action green screen, which was complicated because we had to match lighting, body pose, everything.”
 
In one shot, for example, the digital Superman flies through a tunnel of flames, and right after he lands, as he starts to stand, the camera pulls into a close-up and Routh’s image replaces the double. “We had very particular things worked out about how he flew,” says Hoover. “We used his arms aerodynamically and his knees to turn and create wind resistance like a rudder on a plane.”
 
How fast does he fly? Although it might not be apparent in the shots, the animators could see in Autodesk’s Maya that he flew over 1200 miles per hour. “That made it difficult for the cloth simulation,” says Hoover. “The physics don’t work.” Superman’s cape had to look like Superman was flying faster than a speeding bullet, but it also needed to look pleasing. For cloth simulation, the crew used Syflex software and devised techniques to sculpt the shape using parameters and forces. To replicate the patterns on the real cape, CG artists used Pixar Render Man shaders, which scattered light in specific ways.
 
“It was very complex to get the material to fold in one direction, ripple in another, look like it was going fast, but moving with a certain amount of amplitude that was acceptable to us,” says Hoover. Simulations based on physics do what they do, but the end result wasn’t always what we liked, so we used sims to do the physics and other controls to manipulate it. We had dozens of shots where we replaced the real cape with the digital cape.”
 

Imageworks used the Light Stage 2 system to capture photographic textures of actor Brandon
Routh’s face that they applied to a 3D model for close-up shots of Superman flying.

 
Animators blocked out, roughly, how they wanted the cape positioned, and then Jones worked with technical director Takashi Kuribayashi to set wind direction, speed, and other parameters. “We tried layering small, fast simulations onto larger ones, but it felt like the cape was fighting itself,” Jones says. “We ended up simulating the cape at low resolution for fast shots and higher resolution for slower shots to get more wrinkles and folds.”
 
Kuribayashi also helped the animators with hair simulation, for which the crew used Image works’ in-house system to help preserve Superman’s famous curl in the middle of his forehead. “If his hair blew back, he looked less like Superman, but more like Brandon,” says Jones. “But if that’s what it did on the green screen, that’s what we did, too.”
 
 
Digital Superman flew 1200 mph in Autodesk’s Maya, using his arms aerodynamically and his
knees to turn and create wind resistance.
 
In addition to its own shots, most particularly the sequence early in the film in which Superman stops a plane nose-diving into a baseball stadium, Image works provided its digital Superman to other studios for close-ups. “Our mandate was to make him ready for anything,” Hoover says. “If Bryan [Singer] needed him in any shot, we could come to his aid.” In doing so, the studio pushed digital stunt doubles out of the background and into the limelight.
 
“One thing I wanted to do was give the majestic flying sequences to Image works,” says Stetson, “in particular, the ‘listening post’ sequence, where he sees Lois in her family situation and realizes what he’s lost and flies to a point in space and hovers. It’s beautiful. Also, Superman’s flight in the end sequence is graceful and almost playful.”
 

Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net.  
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