Galactic News

Saturday September 7, 2002
Homing Beacon #68

The latest Homing Beacon has arrived, and today we get to talk about the Clones! The description of the shot is deceptively simple. Queues of clone troopers receive their helmets from an armory dispenser, while Obi-Wan Kenobi and his Kaminoan guides walk by in an overhead corridor. "There are several hundred rendering layers in this shot, not including the bluescreen and miniature elements as well," reveals David Meny, a Computer Graphics Supervisor at Industrial Light & Magic.

Working from concept art devised by Alexander Laurant of ILM's Art Department, this shot is rooted in reality with a number of live action elements. Firstly, footage of Ewan McGregor as Kenobi was shot on a bluescreen stage. "This element was flopped left-to-right, so that Obi-Wan's walking direction would be continuous throughout the sequence," explains Meny. "It was also shrunk significantly in the frame so that the focus would remain in the foreground."

With the live action element positioned, an animatic was created to determine correct camera lens and framing. That virtual camera data was taken to the motion control stage and miniatures of the glassy skywalk and the background dome interior were photographed in multiple passes. "These were shot with miniatures because they were static elements that could be reused for several shots in the sequence, each filmed from a slightly different angle. They also served as great bookends for the whole sequence and gave us something to match our computer graphics to," says Meny.

In the foreground are the clones, entirely computer-generated. "Since we are seeing thousands of these characters on the screen at a time, a lot of time was spent making variations in their armor." Scuffmarks and rank coloring diversify the crowd. Their movement was supplied via motion capture sessions, supplemented with some key-frame animation. The animation was divided into three portions: standing in line, picking up and donning the helmet, and walking back. "We're using the Maya software application and a particle system in Maya, to drive the performances of the characters. The particle system allows us to script when each of the characters transitions from one cycle into the next. By choreographing the performances with Maya's particle system, we can render hundreds to thousands of characters in a single shot very efficiently."

The armory, jokingly called the "bowling ball dispenser" by the artists, was a computer model. "Computer graphics were used because it was a single model that needed to be used only for this shot, and would require a lot of interaction with the digital characters," says Meny.

Pools of light, reflections, cast-shadows and layers of atmospheric haze help to blend the disparate elements together. These are rendered separately and composited together to allow for efficient tweaks of just one element.

Filling out the backgrounds are dozens of non-armored clones undergoing combat and calisthenics routines. These were less detailed computer models since in the finished film, they would appear only in the background. "Because we were seeing thousands of these models in subsequent shots, we created two different uniform colors to add some variation to the squads," explains Meny. "Twenty-nine different performances were recorded and motion-captured."

Since this was the only shot of unhelmeted yet armored clones in the movie, a CG model of a clone bearing the likeness of a young Jango (modeled from actor Bodie Taylor) was specifically designed. However, when it came time to don the helm, it became apparent that the computer artists had to fudge some of the real-world measurements. "The model of the helmet didn't actually fit on the digital Jango's head," says Meny. "His head was too large, so parts of his cheek and nose were actually poking through the helmet. The animators had to enlarge the helmet and shrink down the face slightly to so that they would actually work together and the audience wouldn't see any artifacts."

Posted: by Jedi Power