Unable to generate a valid starting location

[Night-Pryanik]

Describe the bug

Trying to start a game in a "Experimental Cell" starting location of "Challenge - Lab Patient" scenario results in a "Unable to generate a valid starting location" error.

Steps To Reproduce

1. Select "Challenge - Lab Patient" scenario.
2. Try to start a game in an "Experimental Cell" starting location on default game settings.
3. Observe error popping up.

Expected behavior

No errors, normal game start.

Screenshots

Versions and configuration

• OS: Windows 10 Pro x64
• Game Version: 0.D-9139
• Graphics version: Tiles
• Mods loaded: default only

Additional context

Error occurrence isn't consistent. Sometimes game successfully generates this starting location. I understand that's because game can't find a suitable lab in 3 overmap tiles radius, but I think that shouldn't happen at all on default settings.

[dragonlotion]

Getting the exact same issue on the "Challenge - Abandoned" start (city size 16, city spacing 8, no building mods)

[M1nks]

I have also been experiencing this. Firstly with the 'Scavenger Survivor' in multiple worlds and now I've just tried a standard survivor starting in a 'safe location' (City size 0, spacing 8) and received the same error. I've tried different builds and different worlds with the same result.

[UndeadMoose]

Getting this a lot with the new overrun scenario

[jkraybill]

Just got this same issue with "High Tech, Low Life" scenario. I am running 0.D-11520-g71ee31c and the following mods which may have affected this: More Locations, More City Locations, Urban Development, Fuji's More Buildings, Beta National Guard Camp. City gen parameters like size/spacing are at default. Have not attempted to reliably reproduce.

[wapcaplet]

I get this if I create a world with city size < 4, and start with the default "Evacuee" (fixed starting scenario) which depends on having an Evac shelter in the world.

Looking at data/json/overmap/overmap_specials/specials.json, if I've understood it right, none of the Evac shelters can spawn near a city smaller than size 4:

"id": "Evac Shelter",
...
"city_sizes": [ 4, 12 ],

Using world city size = 3, I sometimes get a good start in an Evac shelter, but usually not. With world city size = 2, I always get this error about no valid starting locations.

[Foxtrot-Uniform42]

I think this issue can be resolved by reverting this PR #28959
or at least make starting location search radius higher (e.g. 16)

[actual-nh]

How about, after a failure to find a starting location, a question to the player for whether to try again (e.g., generate a new world and use a higher radius (3, 4, 5 or 3, 5, 7 or whatever)), adjust the world parameters, or try a different starting location?

[anothersimulacrum]

This issue occurs either because the player/developer of the location has settings such that it is impossible to place, making the radius bigger doesn't really improve anything other than spending more time trying to place it (and there's a tiny chance it randomly succeeds).

[actual-nh]

Hmm. Just saying "adjust the world parameters" is a bit too little information, I would think... probably would require autodetection of at least the most common cases (city size not within range, city density too high for a location to be that far from a city, and whatever others there are).

[Night-Pryanik]

I think simple "try again" would help in any case. At least in my experience resetting the world and trying again always worked.

[Foxtrot-Uniform42]

I think simple "try again" would help in any case. At least in my experience resetting the world and trying again always worked.

This is what I do too.

I don't know how is starting point location algorithm is written, but if it gradually expands radius to find a matching starting location, then there is completely no additional time spending on it for default settings when location found at first overmap tiles. It is just a QoL for those players who messing with city spacing and size, since on fail you will re-create world either way and try again.

[moxian]

As of today (see #54600), the error message is slightly better (it tells you what starting location it tried before failing), but is still very confusing. There's not much info to report, and the value of the report is somewhat questionable ("yeah, this is still a thing, we know").

I second the introduction of "Try again" button, since trying again manually (after being booted to main menu) worked just fine in my case.

[WhitePaperWraper]

Get this message almost always with the "island prison" start.I even think one of the worlds was able to generate it once, but not after that.
OS's: linux, tiles. Same results on the Unstable builds released right after 0.F-3 and one 2022-01-29, so I imagine all of the builds in-between would work the same way