New Eve placement algorithm
April 24, 2018
The way Eves are placed has a substantial impact on the feeling of the game. Whenever a player joins the server when there is no suitable mother for that player, that player spawns as a full-grown Eve instead of as a baby. Eve serves as the potential root of a new family tree, and her placement determines the opportunities that are available to that family.
Originally, Eves were placed at random inside an arbitrary radius around the world location (0,0).
This worked fine for a while, until that area began to fill up with civilization. Eve is supposed to feel like a fresh start, with maybe a small chance of stumbling into the ruins of a past civilization, or eventually bumping up against a living, neighboring civilization. As the center of the map got full, Eve was always just a stone's throw away from a village. Furthermore, with everyone so close together, there was no danger of losing a village if it died out. Thus, keeping a village alive meant nothing. We could always find our way back to revive the ghost town tomorrow. Even worse, as these areas got ravaged by human activities, the resources that a new Eve needs to bootstrap became more and more scarce. Eve does need a somewhat green pasture to found a new civilization.
The next Eve placement algorithm involved a random walk across the map, looking at the last Eve location and making a random jump 2000 tiles away to place the next Eve. There can be some randomly-occurring back-tracking with this method, which means that Eve can sometimes end up near the ruins of old civilizations, but we expect such a random walk to eventually explore the entire map, so we will also get farther and farther from center over time. And with many Eves dying without founding new civilizations, and also perhaps due to biases in the random coordinate generator, we quickly walked our way from (0,0) out into the 50,000's. This meant that villages were generally too far apart to interact with each other. Still, Eve was usually in an untouched area full of natural resources.
The next Eve placement algorithm was radial, placing Eves randomly at a radius of 1000 from a fixed center point. This put all villages within trading distance of each other, and offered plenty of untouched space for Eve---for a while. But soon, the "rim" of the wheel filled up with civilization, and we were back to where we started---Eves placed in a crowded area that was stripped bare of natural resources.
The latest Eve placement algorithm was suggested a long ago by Joriom and maybe a few other people, and involves an ever-growing spiral around a fixed center point. This guarantees that Eve is always in an untouched area, but also that she is never too far from some recent civilizations, so trade can happen.
While a server is running, the placements look like this:
You can see the three initial Eve placements at the center, which the server permits at startup to ensure that the first few Eves can have a chance to bootstrap a village in that spot. After that, the spiral ensues, and would keep going as long as the server was running.
What happens when a server shuts down though, as it does every week during updates?
First, the death location of the longest-lineage person during shutdown is remembered. This is used as the "center" of the spiral at the next startup, and after startup, the first three Eves are placed near there. After that, a new spiral grows around that new center point, like this:
As this new spiral grows, it will cross through the previous spiral like so:
That is okay, because any of the other civilizations that were active at shutdown will potentially be rediscovered by Eves, which makes for an interesting Eve variation. Still, future Eves will not be trapped in these already-developed areas, as the spiral will continue further out into untouched areas again.
Also, some of the older, long forgotten villages in the old spiral will be wiped when the server restarts due to the 24-hour abandonment cut-off. Thus, the new spiral will cross through many now-wild areas, even as it overlaps the old spiral.
As the new spiral grows bigger, it will eventually engulf the old spiral and move beyond it, but the overlapping area will always be substantially less than half of the new spiral. Thus, even if 100% of the old spiral contained active villages that were not wiped, more than half of the Eves in the new spiral will be placed in untouched wilderness.
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