How does Thebes have access to corn?

[Donald Duck1]

Hi all, I just settled the first city, built a worker and farmed the corn, and it immediately got connected without a road. How does the connection work? Is it via the eastern river, to the ocean outside cultural borders, ignoring the icepack and back via western river?

I thought connections via coast/rivers had to be within cultural borders? And the ice-pack?
[edit: srry for duplicates, I thougth the uploads had failed...]

 

[sampsa]

Adjacent river tiles are connected, even when the graphics don't look like that. Zoom out (mouse wheel) and click on the trade route icon on bottom right to see all the tiles that are connected. Top left area is connected too, unless I'm wrong.

 

[Pangaea]

I seem to recall reading from a thread similar to this one that the "mouth" of rivers function a bit differently to normal river tiles, and they can "bleed" out to neighbouring tiles for trade routes purposes. That may explain why the corn is connected to the city, although it really shouldn't be (unless it was intended to work exactly like this, that is).

 

[Donald Duck1]

Trade group screenshot:

The top-left part is not connected, so I suppose it must be the hill 1S of Thebes, which perhaps connects both rivers?.
Anyway, I'll look for similar situations in the future, can save some worker turns for roading.

 

[sampsa]

I suppose it must be the hill 1S of Thebes, which perhaps connects both rivers?.

That doesn't make much sense though. I mean, I fail to see how the hill plays any part, but you are right that somehow that that tile somehow connects the southern parts. These things are a bit weird so I just always check it by zooming out.

 

[Pangaea]

Going by the picture, it looks like that mouth of the river thing does indeed impact things, combined with the other river. These things can be a bit weird, but it's cool with surprises like this that saves a few worker turns in the early game.

 

[drewisfat]

I think I can connect the dots here. I'm not DanF though, this is a piecemeal understanding from my own experience, so grain of salt. It is *not* that the hill south of the capital is on both rivers connecting them. That hill is only on the right river. It's behind the flow of the left river and would not be receiving the commerce / fresh water from it, just like how the tiles 3N and 3N1E of the capital aren't river tiles.

Trade groups must start somewhere, usually cities. The capital is on the east river, and so that whole river (in culture) is instantly added to a trade group. The small river on the left is not activated by the city. However, as Pangaea was alluding to, mouths are special. The mouth is visually 1S of the corn but in reality also includes the corn, as the river itself is just one tile long between two tiles. So once the borders popped to include the corn tile, that tile acts as if it's a harbor or city or whatnot, essentially activating that river as a trade group. The game then shows all the tiles that are in a trade group and combines them into one if they're adjacent - it's moved past rivers at this point. So, like Sampsa says, the game doesn't know and doesn't care that the rivers don't actually connect. The NW river would connect by the same logic except it hasn't been activated yet. If you put a city on it, or if there was an ocean dipping down such that the wine tile was a river mouth, it would be connected to the capital as well. This situation happened to me in the Boudica CB game where my corn and even 2nd city were all connected because the incense tile was a mouth. (The road on it was unnecessary and built after the fact with extra worker turns).

 

[Donald Duck1]

Thanks for your responses. I checked again with the starting save, and the trade groups are the same as above immediately when founding Thebes - except that only the 3x3 area around Thebes are shown to be in trade groups. So this is before the border pop.
@drewisfat: I don't understand your explanation on how the trade group of the small river is combined with the trade group of Thebes. But anyway, the trade group view shows that it is connected, so I can take that information into account in the future.
Didn't even know about the trade group view despite playing for so many years... so thx for the pointer @sampsa.

 

[Donald Duck1]

Couldn't resist looking a bit further, so I tried some different locations to settle, which only showed that ocean gets a different trade group, indeed ruling out the connection via coast. Then I played a bit in Worldbuilder (which I never do, so maybe I just did something stupid), and I noticed that erasing rivers does not erase the trade groups. So then I thought, doesn't the map generator make some last minute changes to your starting location in order to ensure access to specific tiles within the BFC if you SIP? Could it be that one such change involves removing a connecting tile (such as a river), and that the trade groups are not updated accordingly either?

 

[Pangaea]

Spent some time trying to find the thread I had read about this, but it's difficult. It could be 10-15 years old, and maybe terms like "river mouth" wasn't used. But I did come across a similar situation in a BOTM game, namely BOTM 170. The gold is auto-connected (without roads), although it looks like it shouldn't be.

Spoiler :

You can play around with this in the World Builder and see if you find out the ins and outs of it. For example by adding culture to the city (so it gets another ring) and then play with the other river mouth further north.

 

[Donald Duck1]

Thx, been searching myself and found several interesting threads on trade routes and connections, but nothing yet that makes me understand the Thebes issue.
As for the BOTM170 case, indeed it seems that gold is not connected to river, however in this case the extra commerce on gold shows that it is (at least, that's how I understand it).

Also, I did settle a second city North at river, but it remained in a separate trade group, so 'activating' the trade group didn't change anything there.

 

[Donald Duck1]

@Pangea Your culture suggestion was great. If I put another culture on the hill 1S of Thebes, the trade group is split. So it must be that hill that connects the 2 subgroups, I suppose.
Also, if I go into Worldbuilder before making a move, do an 'erase' on the tile 1E of Thebes, it erases the forest as well as the river south of it, splitting the river in 2. It also cause the hill 1S of Thebes to lose its commerce. If I then settle Thebes, the corn trade group is also separate.

I just don't see how the hill can connect. The fact that the hill loses its commerce also confirms it is not connected to the south west river.

 

[Donald Duck1]

This thread seems to deal with the same problem: https://forums.civfanatics.com/threads/river-and-coast-network-acting-strange.212929/

Ammar's makes sense to me: "If two rivers are only a tile apart, it's one river for the purpose of trade connection. I'll look if I can find an example in a game of my own."

The thread shows two cases of two separate rivers 1 tile apart, diagonally, and being connected. I guess the hill 1S of Thebes is a third case. Works for me

 

[Spielban]

you can find the similiarity easily

 

[Donald Duck1]

Check!

 

[drewisfat]

Well now I'm confused. Couple screenshots throw river mouth explanation out the window. But they all contradict the initial evidence that NW of the capital in the first screenshot is not connected.
Is it as simple as, we need a resource improved to show the trade group, because otherwise it doesn't matter? Can we improve the wine and unimprove the corn and see what happens?

 

[Spielban]

Well now I'm confused. Couple screenshots throw river mouth explanation out the window. But they all contradict the initial evidence that NW of the capital in the first screenshot is not connected.
Is it as simple as, we need a resource improved to show the trade group, because otherwise it doesn't matter? Can we improve the wine and unimprove the corn and see what happens?

as you can see, it has nothing to do with river mouth. it is the HEAD of river that connect them
and two rivers are just connected no matter what. no need to rely on any improved resources, cities or forts or whatnot

river flows edge of tiles. and we can say head of river is center of 4 tiles.
in initial screenshot of this thread, [1S1W,1S,2S1W,2S] of Thebes are the 4tiles.
two of them(1S1W, 2S1W) are fresh water by the 1-tile long river. the other two(1S,2S) are not.
but one of them(1S) is fresh water by the other river. and that tile(1S) connects them.

but any of (1S,2S) are NOT adjacent to the northwest river. so the wine would not be connected even if it is improved.

 

[Donald Duck1]

Is it as simple as, we need a resource improved to show the trade group, because otherwise it doesn't matter? Can we improve the wine and unimprove the corn and see what happens?

Sure, with Worldbuilder I put a winery on wine before playing, and it has no effect on trade groups:

Attached the starting save as well.

 

[Donald Duck1]

And just for completeness:
1. trade groups after 1st border pop

2a: same as 1, after changing culture of many tiles except the hill 1S in WorldBuilder
2b: trade groups corresponding to 2a.

3a: same a 1, after changing only culture of the hill 1S in Wordbuilder
3b: trade groups corresponding to 3a

1:

2a: culture

2b: trade groups

3a: culture on hill 1S

3b: trade groups

 

[Donald Duck1]

and then I modified terrain such that the desert hill 2N1E touches 4 different rivers in each of its 4 corners (see below for screenshots):
1. Other culture on all tiles that touch 2 different rivers on their edges/corners
2. Corresponding trade groups: all disconnected
3. Same culture on all tiles
4. Corresponding trade groups: all connected

The one thing not clear to me is the case similar to case 1, but with the desert hill itself having Thebes culture. In that case the trade groups remain disconnected, even though the condition for connection seems to be met. Maybe both banks of the rivers have to be in same culture in order to have connection along that river?
5. As 1, but desert hill gets yellow culture
6. Corresponding trade groups: same as in 2.


1. Other culture on all tiles that touch 2 different rivers on their edges/corners:

2. Corresponding trade groups: all disconnected

3. Same culture on all tiles

4. Corresponding trade groups: all connected

5. As 1, but desert hill gets yellow culture

6. Corresponding trade groups: same as in 2.