Video: Click Here to see raw footage of the gladiators' entrance into the arena; computer compositing of spectators; rendering of the Colosseum; inserting crowds in the stands; compositing backgrounds with the principal actors; and the finished shot.
Friends, Romans, Countrymen, Lend Me Your Bytes
Building a virtual Rome was one thing; populating it was something else. To fill the screen with teeming hordes of citizens, the FX crew used two different techniques involving scanning or mapping images of extras into a computer for further manipulation.
"I'm a big fan of being able to shoot real things, map them onto other things [computer models] and then move them around [within the image] and place them and re-light them," Nelson said. "So when you look at them they look real because they are real, but they're been rearranged inside the computer."
One method required extras to be shot from different angles on PAL video wearing blue fabric against a green background. The computer could then erase the green background and replace the fabric color with any wardrobe color of the artist's choosing. That "paper doll"-like Roman could then be placed anywhere within the frame. "We had discrete control over each person. So we could make the audience start cheering at the bottom and go to the top. We could have made them do the wave if we wanted them to."
Another technique involved taking still images of costumed extras and mapping them onto 3-D computer figures that could then be manipulated. "It's like taking a mannequin and projecting a slide on it, and sticking that texture to it," Nelson said.
"Then we used a technique called motion capture where we actually captured the actions of people walking, talking, leaning out doorways, waving at their friends, working on the roof, manning machinery. This data we used to animate the people, and the real textures we shrink-wrapped onto them provided the texture of their skin and clothing. And then we relit them and put them on top of the Colosseum, streaming in or hanging out in the streets, cheering as the chariots came in and whatnot."
Video: Click Here to see elements of the "Blimp Shot" — raw footage on location at Malta; CGI crowds; and renderings of buildings and the Colosseum.
There were a total of 90 FX shots in Gladiator. (Another 30 planned shots were cut when the movie was being trimmed down to 2 ½ hours.) "Some of the other films we're competing against have lots more FX shots, but very few films have a 26- or 28-second visual effects shot," Nelson said.
"That's inordinantly long because of two things: modern audiences are raised on MTV and commercials and they're used to incredible detail every one or two seconds; and also as you look at a visual effects shot you have a long time to pick it apart. So not only did our shots need to look good, they had to have incredible amounts of detail to sustain the screen time."
Pixelated Soldiers and Digital Firepots
Detail was key in the film's opening sequence, when General Maximus leads his army into battle in Germania. The filmmakers were limited in the number of extras they could hire, the number of catapults they could construct for the conquering army, and the size of the location (a forest in Surrey, England).
"Basically, in the old days, Stanley Kubrick would have hired the Spanish army to do that," Nelson said. "But you couldn't do it today, those shots would be too expensive."