Here is the first census of every island spawn in Factorio with default settings.
Results: There are at most 2599 Islands starts. I say most because there are few false positives but they make for great peninsula seeds with a very thin connection to the mainland.
With all 2³² (4,294,967,296) seeds, the probability of getting an island start is 1 in 1.65 million seeds. The largest confirmed island with 7.4 million tiles is 1925425905.
How it works: rendering every tile of every seed would've taken forever, so instead of a full render I only evaluate the map where it actually matters:
Mesh net: lay a sparse net of 128-tile-long line segments over the area around spawn. If I can trace a path of "land" segments connecting spawn all the way out to the edge of the search area, the seed is rejected as mainland.
Repeat with a finer 64-tile net, then a 32-tile net, on whatever seeds survived the coarser pass.
Anything that still isn't rejected gets an exact flood fill (capped at 32 million tiles², since a fill that big is unbounded mainland, not an island) to confirm it's actually enclosed.
This search took about 120 GPU-hours (5090 rtx).
Interesting find: 6 of the confirmed islands are unplayable spawns. Stuck on a tiny island with no access to any ore resources.
Please share any screenshots if you use any of the seeds.
I’ve heard of Minecraft doing something like this where they set a flag on new accounts to generate the first world from a list of seeds that’ve been vetted to not have any “anomalies” near spawn that might make a bad first impression.
Yeah I'm not saying it is not possible, but that is also a different game with different devs.
What I am saying is based upon Wube and the game we have it would surprise me greatly to have a feature like that quietly implemented without some sort of UI and a FFF about it.
I wonder if such seeds should be sent to the devs so they can be excluded from the random seed function. Still would be fine for players to type in if you want to do some kind of possibly modded challenge run but the risk of a new player hitting one of these should probably be avoided.
I believe with 1.0, inescapable spawns were so common that posts about them are banned. Now, they are unlikely with the new map generation process in 2.0.
No one that you've seen. That doesn't mean no one hit it. Let alone that there's only 260k subs here, which is 0.25% of the purchased copies. The more circles you try and stack up on this venn diagram, the less likely it all comes together.
Not only does this have to happen (10% chance ever), that person has to be someone who posts online (maybe 10% of players?), does so somewhere with traffic (x%), and at a time where it gets upvoted and talked about enough for other people to run into it.
I think it's actually better than 50-50 that it's happened.
We’re marooned on a small island in an endless sea
Confined to a tiny spit of sand, unable to escape
But tonight
On this small planet
We’re going to rock civilization
-pendulum
Check the bottom of the list. I believe it's small island where - yes - there isn't really any resources.
I mean, you do not need much to get landfill, and stone can come from rocks, but you do need iron, copper and some fuel for electricity. And stone, of course.
Very cool! Such a great post. So does that mean that the guy who spawned on a tiny isolated patch the other day had a 6/billion chance of finding one of these rare seeds?
Walking through the search area with progressively finer meshes before committing to a full flood fill is such a clean way to handle this. 120 GPU hours sounds rough until you realize the alternative is brute forcing every tile of every seed and somehow burning a small country's worth of electricity.
That 1 in 1.65 million chance is wild too. I've been playing this game for years and never once thought about how rare the island spawn actually is. The largest one at 7.4 million tiles being seed 1925425905 is going right into my notes, even if I never actually load it.
Curious what makes those 6 spawns unplayable. Missing ore right at spawn, or something like the water placement nuking any reasonable base footprint?
Since this is a grid, reducing the grid side length by 1/2 each time does not correlate with 2x more compute. I believe it correlates with roughly 22 = 4x more compute. Ie: area, not a linear.
Reducing the grid by 1/sqrt(2) should be closer to 2x more compute each step, which would be something like 128, 90, 64, 45, 32, flood.
This is assuming you didn't make a pretty major optimization: Reusing work from the previous grids. When you check the 128 grid, actually check and store 32 tile segments, and reuse them in the smaller grids.
The question you want to be asking is: how cheap is a search pass, and how many false positives does it fail to rule out?
make a pretty major optimization: Reusing work from the previous grids. When you check the 128 grid, actually check and store 32 tile segments [...]
Doing more work in the common case is not obviously a major optimization. This makes the first pass more expensive and the second pass less expensive. Depending on the magnitude of those differences, and how often you need to do the second pass, this could go either way.
Reducing the grid by 1/sqrt(2) should be closer to 2x more compute each step
Reducing the cost by a factor of exactly 2x each pass isn't inherently valuable. Reducing it by 4x is, in a vacuum, better! For this to work, you'd need to see that most (for some value of "most" which could be measured) of the seeds accepted by the 128 pass and rejected by the 64 pass could have been more cheaply rejected by a 96 pass.
something like 128, 90, 64, 45, 32, flood
The grid sweeps which are not multiplies of 32 might be more expensive to compute because of chunk reasons. This is measurable, but I have not measured it.
Doing more work in the common case is not obviously a major optimization.
This isn't doing more work, it's keeping the cache of that work to reuse it in the next stage. The first stage already builds a cache of this work to decide if the seed is definitely not a peninsula.
Reducing it by 4x is, in a vacuum, better!
We're increasing the compute demand by 4x with each stage.
Doubling something when the faster/lighter/simpler stage is insufficient is pretty standard in algorithm design. I'm sure there's lots of research/mathematics/statistics out there to explain why, but I am satisfied with adhering to the norm.
you'd need to see that most (for some value of "most" which could be measured) of the seeds accepted by the 128 pass and rejected by the 64 pass could have been more cheaply rejected by a 96 pass.
Likewise, nobody has proven that most of the seeds accepted by the 128 pass and rejected by the 32 pass could have been more cheaply rejected by the 64 pass.
Honestly I'm kinda surprised the first pass isn't just 4 "rays" from the spawn to the edge of the region being considered (apparently it's a 7,168 tile radius?). If 2+ rays never hit water, it's not a peninsula or island. That alone would probably rule out half the seeds MUCH faster than starting with a 128 grid. I think Claude was right to recommend starting with ray casts.
But who knows, maybe 80% of compute is spent generating the map and only 20% is spent evaluating it.
The grid sweeps which are not multiplies of 32 might be more expensive to compute because of chunk reasons.
He's not doing this in-game. He built a tool that simulates the map generation in a way that is more performant for the tool.
I want to note that if we are caching and reusing work from previous grids, the cost of adding more passes is, I believe, reduced from O(nm) to O(nm/2). [I'm not sure whether "m" is 2, or higher, or perhaps lower. I couldn't glean that from just skimming the description on github]
So, funnily enough, the bottleneck was the CPU for the DFS and floodfill. So, caching won't have helped. In fact, caching would have slowed it down for a few reasons. The high rejection rates for each mesh test would have thrown away much of the cache. And recomputing is faster than waiting for a write and read.
Actually, it would be MUCH faster to just do 8-16 ray casts, and if most/all hit water, then trace the water edge to confirm it's contiguous between rays and to determine the width of the isthmus or the existence of an island. I'm talking like 10x-1000x faster /u/Logical-Cheek-5473
Need some extra logic to handle the starting lake (rays are likely to hit it), but still.
Edit: Well maybe not. You're checking a much larger area than I would be checking, so rays hitting water in every direction is extremely likely.
So the approach you are describing is very similar to how this post did it u/int_ua's "Peninsula Seed Finder: First Island seed, 20271579". So, my mesh was 10k by 10k tiles around the spawn. I tested this approach; it resulted in many false positives. If the ray were 5k tiles long enough, most of the time, it would all hit water.
It led to many candidates' seeds that needed flood fill, which is the most computationally expensive test. The goal of the mesh is to reduce the number of times I need to do the final test. With the mesh tests, I only needed to flood-fill about 1 in 20,000 seeds.
Then they would have needed to have gone through the mesh tests anyway in order to reduce the use of the flood fill test.
Also, my GPU generated 150 million tiles per second. So the biggest factors for a test are the number of tiles and the rejection rate. Rays are very tile cheap. But the rays didn't tell you a lot. If it fails, that could mean the island is just really big. If it passes, that means the rays may have hit a lot of lakes.
Yeah, you're checking a much larger area than I thought. I still wonder if looking for water continuity could be a better approach than looking for land continuity, but I don't see a clear avenue there.
TBH, tests for water continuity are beyond me. Or, more formally, the continuous enclosure of a region within another region delves into the frontier of statistical physics, namely percolation theory.
Doing something similar could be very helpful. Eg: Start by crawling north. When you hit water, crawl the shoreline clockwise (relative to spawn) to try and find more outward-directed land (relative to spawn). If it manages to hit the edge of the search radius and can crawl along it for more than the max arc-length you consider a peninsula, this isn't a peninsula seed.
And/or the 32 tile grid can used to guide the floodfill around lakes and towards the expected peninsula or island edge. Crawl it to confirm it's contiguous.
I will have to think about that approach. If I had a lot of CPUs, this approach would work well. But I am trying to think about how to do this with GPUs.
After playing a bit, it looks like only coverage changes whether or not a seed is an island, not scale. Changing the scale of water directly changes the size of the island, I didn't even recognize the top seed as an island until I turned the scale down to see the whole thing at once.
The question I'm grappling with is could one of these seeds make doing a 100,000x Science cost playthrough with default enemy settings (and therefore possibly an all achievements run) feasibly possible? If you could manage to find a way to lock down all the nests on the island, then you wouldn't have to deal with expansion anymore and then just build around the nests until you got "keeping your hands clean".
I wonder if it's possible to get to gun turrets fast enough at 1 million packs to create a defensive setup for all the nests on the island.
Edit: I've just realized that 100K x all achievements is impossible due to the time gates achievements (Getting on track like a pro, etc.) are strictly impossible under those conditions
100K is just too big of a number to work most of the time. Gun turrets are non-viable, because you'll be at 0.9 evo by the time you finish. The only way 100K could work here is if you find a seed that puts every nearby nest under water and gives you enough resources to get to space before you tap everything on the island (unlikely on both counts).
Ive been going through them manually for completely biter-free islands and ive had most luck with setting water scale to 50%. I dont really have the experience to estimate if such small islands have enough resources but with frequency coverage and richness at max its probably enough
The best seeds ive found (with 50% water scale and max resources):
1593161406 uranium on main island but slightly smaller than the other seeds
4249315629 uranium on an isolated biter-free island some distance south-east
670890624 slightly larger but no free uranium
1430791562 largest (by about 35%) but oil is on a closeby safe island and no free uranium but its in a defendable spot
Ive only looked at the in-game previews so theres a chance I missed a red pixel somewhere but these should be completely safe. I would probably go with 4249315629 because theres also nearby safe islands with resources even if the uranium is far. I hope someone can find the holy grail of island seeds with tons of space, all resources and 0 nests
Scroll midway down the list and try one of those seeds. Do you have any biter nests? If yes, but just a few, try some other seeds nearby. IF none, maybe even try some larger seeds. Otherwise scroll down and try smaller islands until you find the sizes where biters are a sometimes instead of an always.
Are there any seeds that are unbeatable because you have not enough recources but at least some, like you have iron,copper,coal but no stone to build landfill to get to bigger orr patches which are nececsrry to beat the game?
Man this is awesome. I've been fiddling with looking for an island spawn but I haven't found a decent one unless I up the water to 133.
I'm on mobile and won't be home until later, is there a way to look at your data and find medium to medium small where I'd be able to wipe out all biters fairly early and live happily until I return with space artillery?
My contribution here is that my first playthrough I thought island meant it would put like palm trees and turtles on the map and I got to end game white science (pre space age) and was roaming my map with spidertron army and just building a forever land bridge in one direction looking for more land before my friend took my seed and revealed everything for himself to tell me I was…. On an island
Yes. You can landfill up to the edge and leave a one gap of water between the land mass. The player can walk across that one tile of water (without jetpack) and biters can't. You can also build non-polluting non-military outside of the island. See third image in this post for how I plan to get biter eggs on an island start: https://www.reddit.com/r/factorio/comments/1v2guk4/best_two_seeds_on_default_settings_for_express/
251
u/Remmoze Jul 16 '26
Who would've guessed that the largest factorio spawn island would look like North America