A Guide To settlement_mechanics.xml

[Jurand of Cracow]

My takeaway from your testing is: what provide for "population growth from trade" are:
- sea trade even if no grain is involved (not in your testing, but my guess is: the better the buildings, the more growth).
- grain resource for the exporting settlement (but not the importing one) if there's any trade (again, from the Alavaria's observation on roads: the better the trade buildings, especially roads, the more growth).

[Gigantus]

That's pretty much my take as well.

[Jurand of Cracow]

My takeaway from your testing is: what provide for "population growth from trade" are:
- sea trade even if no grain is involved (not in your testing, but my guess is: the better the buildings, the more growth).
- grain resource for the exporting settlement (but not the importing one) if there's any trade (again, from the Alavaria's observation on roads: the better the trade buildings, especially roads, the more growth).

I'm back with the topic since I've seen in game something contradictory. As one may see on the pics (each is actually with addition from another screen) it's possible that:
- a city with only import of grain has a trade-related population growth
- a city with neither grain nor grain import nor any sea trade - also has this type of growth
So it's more complicated...

Spoiler Alert, click show to read: 

[IMG][/IMG]
[IMG][/IMG]

[Gigantus]

Have a look at the fertility levels in descr_regions - maybe high levels also provide a trade bonus.

[Jurand of Cracow]

Have a look at the fertility levels in descr_regions - maybe high levels also provide a trade bonus.

Definitely not - Krolewiec at the pic has a fertility level of 1.

[Jurand of Cracow]

On the growth issue: in another mod (Wrath of the Norsemen) the highest growth from trade I've seen is 3,5%.
[IMG][/IMG]

[Gigantus]

It's linked to the grain import for sure, in vanilla any trade with Alexandria was bound to give a boost due to their multiple grain resources.

Grodnica seems to be a bit of a step child: no trading resources, no fertility to speak of.

[Jurand of Cracow]

Grodnica seems to be a bit of a step child: no trading resources, no fertility to speak of.

This is actually one of the hallmarks of the Wrath of the Norsemen mod: most of the settlements are villages at the beginning having no fertility. Most of growth in the settlements come from trade mechanics.

[reaper101]

Got a bit of an odd problem. Editing the files for the settlement size so I can get citadels more feasibly - and it causes the game to crash when I try to load in the campaign. Upgrade entry for fortress and base citadel size are the same - and I tried editing fortress's maximum to avoid the problem, still got CTD. Nobody has mentioned this - but does editing the xml break an existing campaign?

[Gigantus]

Good possibility for the settlement size, but I don't think the other values (EOP etc) will cause a crash - simply try if a new campaign crashes.