Birds do it. Bees do it. Even educated fleas do it. Maybe. Anyway, some things flock, and sometimes it makes them look more organised than they are. Shoals of fish, for example, can dart away in the same direction at the sight of a predator, coordinating hundreds or thousands of tiny little minds in an instant. There are clearly two possible answers: either fish are telepathic and will shortly rise to masterdom of our species, or tiny little minds can be programmed to think tiny little thoughts that result in these co-ordinated mass movements. Boids neatly demonstrates it is the latter, and puts all our minds at ease.
So does Flocker. And in less dimensions. But Boids is old, and you can't play with it. Flocker, on the other hand, was only born in, ooh, about 2002 or 2003 and is freely available to you guys to proddle with. Simple controls are along the bottom, but the fun bit is changing the variables, accessed by the right click pop-up menu. You can alter the distance within which a creature takes notice of another for each of the three steering behaviours (alignment, cohesion and seperation), you can alter the weighting (i.e. the relative importance) of each rule, you can alter speeds, accelerations, random influences. I always knew the labels for these things were far from informative, but never got around to changing that, and now probably never will, so you're largely on your own. I will tell you that angular measurements are in radians, not degree, so numbers range between 0 and 2*pi (about 6.28). Oh, and the especially mysterious 'forward angle' is the angle which a creature will deem 'in front of' it, and thus if it wants to go in a direction within this angle, it will try and speed up. If it wants to go in any other direction, it will slow down. Pressing space when the main window has focus will pause Flocker. If Flocker pauses of its own accord and will not unpause, however, it has done so to stop itself crashing horribly. A stop-gap solution that never got de-stop-gapped
Despite being convoluted, undocumented, and a bit buggy, this is still a favourite of mine. Watching a flock swirl and fall into a pattern after they are reset it bizarely satisfying. Unfortunately, it's only available in Windows.
flocker.zip - Zip file containing Windows executable.