Not true, Vester. The only randomly generated number is the seed.
I've heard of the butterfly effect occurring from things as small as changing a stone type from vein to cluster, so it's probably something really small you changed.
Yeah, sorry, that's what I meant. The seed starts you off with a world, but in between, something happens.
(So if you gen a world and one civ wins a war over another, and you gen it again with the same seed, will the same outcome happen? I am curious to know.)
As long as *nothing* has been changed on the user end (like the raws), yes. The way it functions is the following:
Computers are very, very bad at doing random stuff, so there's a numbers of algorithms (i.e., somewhat like recipes, for those who aren't too fluent on computer-speak) to make them create random numbers. Only, they're not really random, only look like it. All these algorithms need some entry data, that's the seed. For the same entry data, it always generates the same sequence of numbers.
However, even if the sequence is the same, if what you use it for isn't, it's going to give you a different world. So, if the system has to make even a single calculation more using randomly generated data, there's no telling how the result is going to change. And since we don't really know how DF uses random numbers, unless we do a whole lot of experimentation and/or Toady himself tells us, we have no real way to tell what kind of changes would trigger a different result in worldgen.
Imagine, for example, that you changed something like the damblock of a megabeast. The first time, the megabeast was killed by a dwarf (because I don't believe all those tales of elves killing megabeasts - except for Cacame), but since now it has a higher damblock, the result of the calculation - even with the same numbers - is different. Now DF has to keep track of that megabeast, which it does - I speculate - by using more random numbers, which would have originally been used for other calculations (like Cacame's birth). Voilá, instant change in worldgen.