Troy’s crowd scenes were a real challenge to MPC, which had to develop its own simulation software for the project. Here Greek warriors greet Achilles (Brad Pitt). Courtesy of Warner Bros. Ent. © 2004 Warner Bros. Ent. All rights res

Crowd scenes have always been a major challenge for film directors and a source of concern for producers. In the good old days of silent movies, when a scene required 5,000 extras, well, one just had to hire 5,000 extras. By using prism lenses, a gifted cinematographer could create the illusion of an even larger crowd. With the development of optical compositing, directors managed to achieve the effect in a much more convincing way. A crowd of 1,000 could be created on film by combining five plates of 200 extras.

For several decades, optical crowd duplication would remain the only technique that allowed very large numbers of people to appear on screen — besides matte painting for static crowds. One notable exception is Gandhi (1982): for the funeral scene of the title character, almost 100,000 Indian extras were hired (at the local rate), but 200,000 more showed up on the filming location for free! As a result, the scene now boasts what is probably the largest real crowd ever shown on film.

With the advent of computer generated extras, film directors discovered that they could direct a virtual crowd just as they would with real people on a movie set. Major productions such as Titanic, Star Wars: Episode I and The Grinch pioneered the effect. Everyone’s game was raised with the release of The Lord of the Rings trilogy. For this production, Weta Digital’s engineers developed a revolutionary software that allowed each digital extra to basically decide on its own what it should be doing. Dubbed Massive, this new technology allowed the creation of the most impressive battle scenes ever put on film.

Framestore CFC was assigned the task of creating the Greek armada. There are only two real ships in this shot; the rest are digital.

The Mother of All Battles
When Warner Bros.’Troy went into production, it was clear for all involved that their battles had to surpass these landmark scenes. After all, their movie was based on the greatest battle of all times. Overall visual effects supervisor Nick Davis assigned the ambitious sequences to London-based The Moving Picture Co. “We did about 425 shots, all focused on the battle scenes and the creation of the city of Troy”, explains Chas Jarrett, MPC’s visual effects supervisor. “We started in November 2002 with six months of research and development led by Julian Mann, our R&D supervisor. We knew that crowd simulation technology would be paramount to the success of the battle scenes. Our first option was to simply buy Massive licenses. However, we found out that the software was a simplified version of the program that had been used on the Peter Jackson movies. It didn’t have all the functions that we needed. Plus, it was pretty costly: at $40,000 per license, it was three times more expensive than your regular Maya license. And we needed 20 of them…”

Eventually, Jarrett and Mann realized that they had no other choice but to develop their own crowd simulation software utilizing CG animation and artificial intelligence. A team of 10 programmers worked full-time on the project for 15 months, ultimately producing some 40 different applications combined into one user-friendly program. Two major components of the software were the motion capture database, dubbed Emily (for M.L.E.: Motion Library Editor), and the animation program, dubbed Alice. “There were two steps in creating and animating a CG soldier,” explains Jarrett. “First, we gave him senses: he was able to see, hear, feel the ground under his feet, make the difference between an enemy and a fellow soldier. Then, we told him what to do with this information.”