Virtual Extras

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Software developed by Massive Software, based in New Zealand, which was used to animate the huge battle scenes in the Lord of the Rings trilogy, is also capable of giving animated agents cognitive behaviors, says the company's founder, Stephen Regelous. "As far as I can tell, there's nothing particularly new about this work," he says.

But Badler disagrees: "Ultimately, Massive's software puts considerable burden on the animator or programmer to create the behaviors." In contrast, he says, Terzopoulos's autonomous pedestrians can be created with great ease. "You can assign individual goals, or you can assign them randomly," says Terzopoulos.

Also, according to Badler, Massive's software is practical for animating only relatively short scenes; after that, the amount of time the animator has to spend on the characters becomes prohibitive.

With the autonomous-pedestrian software, says Terzopoulos, it is possible to animate relatively long scenes, dictating the movement and behavior of 1,400 characters in real time. As demanding as this might seem, he says, it is possible because the same set of mechanisms is used for each character--it's just the parameters that vary. "The biggest computational expense is the simulation of their perception, because they have to look at other objects from their field of view," he says.

The end result is pretty realistic, says Terzopoulos. You can follow and scrutinize an individual character within the Penn Station animation at close range for periods of up to 20 minutes. And what you'll find, Terzopoulos says, is behavior quite typical of someone at a train station.

Beyond movies and games, there's increasing interest in using crowd simulation to help conduct fire and disaster assessments of large public spaces, says Jian Zhang, director of the Computer Animation Research Center at Bournemouth University, in England.

In fact, Terzopoulos has already used his software to help archeologists analyze and learn more about the usage of an ancient building, the Great Temple of Petra, in Jordan. "They overestimated the capacity of the theater," he says.

Terzopoulos is now working on using simulations to help design smart surveillance networks. The logistical problems of creating huge networks of security cameras, along with privacy concerns, make it difficult for vision researchers to carry out practical experiments in this field, says Terzopoulos. So the current trend is to start using simulated public spaces instead.