Border calculation

[syndicatedragon]

Does anyone know how borders are calculated? I understand how culture determines the radius of the border around one city, but how does that interact with other cities/rival cities? Is it possible to predict when you will "steal" squares away from a rival civ?

 

[sealman]

Good question. Off hand, I can not recall how but I know that it has been discussed here at one point. I will try to find the thread for you (and for me).

If someone does know the answer, I will not have to go through a time consuming manual search, hint....

 

[Grille]

*AFAIK* the amount of local culture determines that (i.e. city with more culture than rival city gets the tile), but there's also some hard rules:

You can never get a tile that is adjacent to your rival's city center square and 2 or more tiles away from your closest city center square (you could have 10k culture in your city and rival could have 0).
You can never get a tile that is in the fat X of your rival's city (rival city must have had one border expansion or a second rival's city culture covers that tile already) and outside of any fat X of your cities.
(You could only get that tile if rival city has no border expansion)

In case both neighbouring cities have the same amount of local culture, first founded city gets the tile (e.g. cityA-tile-cityB, both 0 culture, A founded before B, A gets tile).

So... if there's a tile that is in the fat X (but not adjacent to any city center square) of two rival cities, city with bigger local culture gets it.
(You'd need to spy the rival city to make predictions.)

 

[Oystein]

First look at the cities culture ring. The closest city get the tile.

When the tile is in the same culturering, I thought (as Grille said) the city with highest culture. But I made a test. The tile did not switch straight away. I had to wait a few turns. Maybe an updating problem.

 

[Tharak]

Originally posted by Grille
*You can never get a tile that is adjacent to your rival's city center square and 2 or more tiles away from your closest city center square (you could have 10k culture in your city and rival could have 0).

I'm fairly certain this isn't true. I believe I've seen a city of mine take that square from a rival civ when my culture was much better than his...

This also doesn't wiork when you settle 2 squares away from a rival civ..eg : YXR (Y = you, x = empty square, R = rival civ). SOMEONE has to control that middle square, that is next to both of your cities...

 

[Wakboth]

Hence, why he said that you can't take a square inside a cities fatX area that is also outside any of your city's fatX area.

If you have a city that is close enough to the other (like in your YxR example), there are many squares that are within both city's fatX area. Which one takes which squares then falls to relative culture. If both cities have some culture in them, this can result in taking squares away from the other's fatX area even if you are two squares away (YxxR), since there's a square's worth of overlap still present. If both cities have some culture and you are *more* then two squares away (YxxnR, where n>0), then you will never take a square from the other cities fatX area no matter what your culture value is.

 

[slothman]

I believe it works this way.
You get all squares within you culture radius with the following exceptions:
1. If it is within 2 rival civs radii then it goes to whichever city it is closer to. If equidistant to both then whichever has more culture. If equidistant and same culture then I think older city.
2. If a square is directly between to of your squres then you get it also.
3. You never get ocean squares only land, sea, and coast.
I haven't seen the fatX area affect this.

 

[Siegmund]

A tile one square away from a city belongs to that city.
A tile one square away from each of two cities belongs to whichever city was founded first.

A tile two squares away from a city belongs to that city once a cultural expansion occurs, provided no other city is only one square away.
A tile two squares away from each of two cities will belong forever to whichever city first claims it.
Similarly, a tile two squares away from one city and three squares away from another city may be temporarily claimed by the more distant city with culture>100, but will belong forever to the closer city if the closer city expands.

If a tile is three or more squares away from any city, it may change hands repeatedly in a cultural tug-of-war, but such a tile isn't of any value except for denying freedom of movement to your enemies anyway.

 

[Qitai]

Slothman is right. The rest are incorrect.

 

[Oystein]

Originally posted by slothman
I believe it works this way.
You get all squares within you culture radius with the following exceptions:
1. If it is within 2 rival civs radii then it goes to whichever city it is closer to. If equidistant to both then whichever has more culture.

Just as I thought earlier, but I have found an updating problem. This will normally not make much diffrence. Since the boarder are recalculated every time a city is build or expands border.

If equidistant and same culture then I think older city.
2. If a square is directly between to of your squres then you get it also.

Just to clearify, this happens when you control the tiles to NW and SE, or NE and SW.

3. You never get ocean squares only land, sea, and coast.
I haven't seen the fatX area affect this.

I dont think you can have an ocean tile covered with a fatX in a generated map. But for an edited map, this is pobbible, and you will get the ocean square.

 

[Grille]

Originally posted by Tharak

Originally posted by Grille:
*You can never get a tile that is adjacent to your rival's city center square and 2 or more tiles away from your closest city center square (you could have 10k culture in your city and rival could have 0).

I'm fairly certain this isn't true. I believe I've seen a city of mine take that square from a rival civ when my culture was much better than his...

I meant such a city placement:
YabR
Y=your city center square
R=rival "
a,b=tiles
In this case, you will never get tile b, no matter what (unless you capture/destroy R).

This also doesn't wiork when you settle 2 squares away from a rival civ..eg : YXR (Y = you, x = empty square, R = rival civ). SOMEONE has to control that middle square, that is next to both of your cities...

This doesn't refer to the scenario described above -
but yes, someone has to control it - if Y and R have the same culture, first founded city gets tile (otherwise city with more local culture).


about ocean tiles:
What Oystein said. If an ocean tile is part of a fat X (1 expansion has happened), that ocean tile is inside your cultural borders.
Such cities are only possible on pre-made editor maps (both standart and large 'earth.bic'-s on the vanilla CD have potential for such city sites).

 

[Chieftess]

I actually asked Ainwood once to figure that out for my culture flip calc... (never got a reply.. ). But, I think it works this way:

1. A city with a higher ranked culture level will take precidence. (i.e., level 3 (1,000 culture) over level 2 (100 culture)).
2. The city that was built first takes precedance over that level (unless the neighboring city has a higher level, then that city is garunteed atleast a 3x3 radius).
3. For immediate city radii (the 3x3 tiles), A city will get that 3x3 tiles if that city has 2 more culture points than the neighboring city.

Also, I think total culture might play a role in this, too.

Do this:

In the editor, give a city 10, then 100, then 1000, then 10000 etc. culture. Watch how the culture borders grow. Try to place a rival city within the culture border. As long as the rival city's culture level is less than that of the origanal city, the origanal city's culture will take over.

It's sounds complicated, but after awhile, you'll see a pattern developing. And that's usually the city's borders try to mimic the culture level, minus a rival city's culture level. I think things become a bit more complex when you have more than 2 cities involved.

 

[Commander Bello]

Originally posted by Grille
[...]I meant such a city placement:
YabR
Y=your city center square
R=rival "
a,b=tiles
In this case, you will never get tile b, no matter what (unless you capture/destroy R).
[...]

Sorry, not quite correct, as you may see:

Btw, England currently has more overall culture than the Byzantins (me)

 

[Qitai]

Here are the rules.

(1) If you have the culture level, you get the cultural border.
(2) If both you and another civ has rights over a certain tile, the city which is nearer gets it. Nearer here means level1, level2, level3 cultural expansion (i.e. 9 tiles, fax X, etc)
(3) If both you and another civ is equidistance to that same tile, then the city with higher culture border gets it. Total culture do not matter at all.
(4) If you have the exact same culture point, the one which is found earlier gets it.
(5) You can never get ocean tile in your cultural border.
(6) A tile in between your cultural border (i.e. NW+SE,NE+SW) automatically falls into your cultural influences unless subjected to rule (2,3,4) above.
(7) There seems to be a bug in updating cultural border sometimes. This, however, should not be delay by more than 3 turns.

To check the above, you just need to do an investigate city everytime you gain or lose some tiles due to culture. It does not take much time to figure that out.

 

[Chieftess]

Originally posted by Qitai
Here are the rules.

(5) You can never get ocean tile in your cultural border.

Wrong. You can get an ocean tile in a modded game if an ocean tile falls within one of 21 tiles in your city.

 

[Catt]

Originally posted by Commander Bello


Sorry, not quite correct, as you may see:

Grille's original point, made a second time in response to Tharak, is that you will never get a tile next to an enemy city if there are 2 tiles between the enemy city and your city. In other words, if C x x C then each city will get at least a 9-tile radius. Only in those cases, such as your posted screenshot, where only one tile separates two cities, i.e., C x C, will one of the two cities control the single intervening tile. Read Grille's post again -- your screenshot does not contradict his point.

 

[Commander Bello]

ooops... sorry, you're correct. My fault, sorry

 

[Grille]

Yeah, the stuff I wrote in post #3 looks a bit abstract, better have some screen shots -I now hope it's sure as eggs is eggs.
(klar wie Kloßbrühe...)

Anyways, the pic has another interesting problem in it: you could e.g. grab that cow tile 2 tiles SE of New London with (e.g.) the next border expansion of New Varna, as long as New London's culture is below 10.
Now the problem (though we cannot see it in the right bottom corner, we know there is one of your cities as well):
Who gets the cow tile, if
-New Varna's border had expanded (so cow *theoretically* grabbed) and its local culture is better than New London's
-New London had 1 border expansion
-'unknown' city in right bottom had no expansion

Cow *should* go to New London in that case, I think.




But total culture (ratio) won't matter. I once made a test scenario with heavily modded cpt rates of certain improvements (for different testing purposes, though). At some point, total culture ratio was like 1:gazillion, but there was no 'unusual' border behaviour. It was always local culture (respectively rules posted above) that determined borders.

Btw, there's another update problem (it's actually a minor bug): Sometimes (e.g. if you get a city through peace treaty), even if the borders are updated correctly, the working tiles' ownership is not: citizens from a rival neighbouring city could work tiles within your borders! There was even a SOTD about it IIRC. The problem normally vanishes in the next turn (maybe as well by 'leave or declare' option, if present).

 

[Qitai]

New Varna can get that cattle only on the 3rd cultural expansion. From the look of it, it may not even reached the 2nd expansion (i.e.<10 cultural point). This, I cannot tell from the screenshot since the 2nd expansion are all blocked or necessary information are outside the screenshot.

And since it only gets it on the 3rd cultural expansion, Whereas New London gets it on the 2nd cultural expansion, New London is nearer and would get it if it has the culture.