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Moriash Moreau: My Second Life
Wednesday, June 08, 2005
The Life Aquatic
After reading this New World Notes article, I took a trip out to Themiskyra to check out Surina Skallagrimson's incredible artificially evolving fish myself. While I was there, I was fortunate enough to run into Ms. Skallagrimson. She explained the basic behavior of the fish to me, and told me how to interpret what I saw.

If you get close enough, you'll see that each fish has a small cyan number floating above its head. This number (ranging from 1 to 11) tells the general greed level of the fish. This factor is set at birth. Take the greed number, divide it by the fish's current health (presumably related to its last feeding time), and the result is the individual fish's hunger level. This determines how actively the fish seeks out sustenance. Food, in the form of small plywood spheres, is periodically produced by small pyramids scattered about the ocean floor. (If you're feeling generous, you can also touch the pyramids to feed the fishes yourself.) One would think that the fish with the highest greed factor would always be at an advantage (and I didn't see any greed numbers below 7). But Surina assured me that lower greed numbers have their own innate advantages in the evolutionary struggle.

If a fish goes too long without eating, it dies. If it's well fed for long enough, it reproduces. And if it manages to stay fed and avoid the hazards of the deep (physics bugs, running off the edge of the world) it eventually dies of old age. As I watched, two or three fish announced "I am so old! Goodbye, world!" and expired.

Each fish is equipped with a sensor, which is used to spot food and other fish. The parameters of this sensor (range, etc.), as well as other physical and behavioral characteristics (swimming speed and so on), vary from fish to fish. When the fish is swimming in a shoal, surrounded by other fish, it is yellow. When it finds itself alone, it turns white and extends its sensor range to search for others. When it turns purple, it senses food. Surina programmed these color changes in order to get an idea of what each fish is thinking at a given time... And, of course, because they're pretty.

I spent the better part of an hour watching the hypnotically realistic behavior of the aquatic life of Themiskyra. It's particularly interesting to center your camera on one, and let it pull your view along with it as it ambles through the briny deep. As mentioned in the article, the fish will periodically form into a large, rough circle as each follows the one ahead of it, turning in a tight arc in order to keep the fish ahead in sensor range. Then, for no apparent reason, the circle will break, and the fish will move on in a loose group. I saw this happen several times, but never could figure out what made it start or stop. Each fish's individual behavior is simple, but the emergent behavior of the group is surprising. And surprisingly beautiful.

Okay, they turn purple when they see food...
Wait a minute! AAIIYEEEEE!!!

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