Virtual Gorillas

By Kathy A. Svitil|Tuesday, April 01, 1997
By this fall, the newest attraction at Zoo Atlanta may not be an endangered white rhino or a giant panda. The creatures in the new exhibit-- a few dozen gorillas--won’t even be alive. They will exist only in a virtual electronic world, a world visitors can enter by donning a helmet that presents a three-dimensional view of the gorilla habitat. With a joystick, a user walks among the apes, becoming an adolescent gorilla. So if the user approaches a male silverback and gets too close, says Larry Hodges of the Georgia Institute of Technology, the silverback is going to give a warning cough--which means ‘back off.’ If the user doesn’t back off, the silverback might charge. The virtual charge can be startling, says Hodges. In tests, users start to look for the move-back button real fast.

The cyber-apes and their virtual world were developed by programmers at Georgia Tech to demonstrate the complexities of gorilla society. But the exhibit isn’t just a sophisticated learning tool. It’s the first accurate representation of animal behavior ever produced in virtual reality, other than simulations of the feeding and schooling patterns of fish. And it’s one of the best depictions of an outdoor environment ever created. Most vr environments are indoor scenes, and humans build things that have straight walls that are perpendicular to one another, says Hodges, who heads the project. Outdoor scenes, however, are much more complicated. The rocks, trees, and grass are all very detailed things, and you need to be able to create accurate representations that you can also render at least 15 times a second. You want the user to be able to look around without the image jerking.

The virtual exhibit is based, to some extent, on the zoo’s five real gorilla habitats. One of the areas--the one-acre territory of a 38- year-old silverback and his family--was re-created down to the last tree stump. We used blueprints of the habitat, says Hodges, and did a lot of photographing and videotaping of the enclosure to make it as close as possible to an accurate representation.

The virtual habitat contains five types of gorillas: a dominant male silverback, subordinate adult males, adult females, juveniles, and infants. Each has its own set of about 16 behaviors--lying, sitting, standing, walking, chest beating, turning in annoyance, charging, and so on. Like real gorillas, the virtual species grunts and screams to communicate.

To make the gorillas behave as realistically as possible, Georgia Tech programmers pored over reference books and videotapes of the zoo’s gorillas. From that information, they created models that they showed zoo personnel. We’d develop a behavior, and then they’d say, ‘Yeah, that’s pretty close,’ or ‘You need to do this,’ and then sometimes act it out, says programmer Don Allison.

The first prototype of the system needed an operator to sit behind the scenes, watching the user’s actions and choosing the appropriate gorilla response from a menu of possibilities, like the Wizard of Oz, says Hodges. Now all that is automated. It turns out that gorillas are fairly predictable, Hodges says. The people at Zoo Atlanta provided us with flowcharts that say ‘if this happens, there is a 40 percent chance you will get this reaction, and a 60 percent chance you’ll get this other reaction.

The program still needs improvement. The gorillas have fixed expressions, for example, their mouths always closed and their eyes always open. Hodges would also like to see a wider range of behaviors, such as the ability to play with virtual adolescent gorillas or to interact with other people using the system.

Another item on the wish list is more ambitious: an entire virtual zoo. The programmers designed the system so that the gorilla habitat and behaviors can be unplugged while some other program runs in its place. At some point we’ll start looking at other animals, Hodges says. Elephants and rhinoceroses might be good candidates, and we’ve already had a call from people at Yellowstone who want to do bears.
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