Religion, how does it spread?

Titus

Armchair Great Person
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Oct 25, 2005
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I think the manual and civilopedia are too vague on how this works, so I'm hoping some knowledgable persons can help me out with clearing the confusion about this. Some of these questions are sort of connected...

1. What exactly is the "influence" on the religious advisor's screen? Is it only affected by the number of cities with the religion and the size of these cities? Or also whether other civs have it as state religion, and how powerful those civs are? Do monastaries, temples and cathedrals in your cities boost the "influence" by boosting the culture your religion generates?

2. Is a trade network connection by roads/rivers/coastlines absolutely necessary for the spread of religion, or does it only affect the speed of the spread?

3. If I'm the founder of a religion, it seems to spread to my own cities fairly quickly. Is the spread slower between the cities of non-founding civilizations (assuming that none of those civs' cities have any religion at all), even if they are as well connected as my own cities, and at same distance (number of tiles) from the holy city?

4. If you count aside missionaries, does a religion ONLY spread from the holy city and outwards, or from any city with the religion? I have sent missionaries to far away cities of other civs, but does the religion spread on from there to adjacent connected cities? In other words, can you with a missionary spread religion in a single city on another continent, and then watch it sprawl across the entire continent eventually (during a considerable time, but still), without any other active measures on your behalf? I have never noticed that this works myself.

5. Does the spread of religion slow down or stop to halt after a certain technology or civic? After a certain distance from the holy city? I get the impression that when I reach the medieval times or so, my religion doesn't seem to spread outwards any more.

6. The manual says that "some religious buildings increase the speed at which a religion will spread", but it's not very clear how, except by the creation of missionaries. How does this work? Do monastaries, temples and cathedrals actually speed up the spread? If so, are they more important in border cities than in core cities?

7. Related question: Does your cultural output (i.e. your cultural superiority/inferiority compared to your neighbouring civs) - by religious buildings or otherwise - affect how fast your religion spread to your neighbours? In other words, are they more likely to adopt your faith if they are awed by you?

8. How does the mechanism for whether a city will adopt the religion work?

In a recent game I founded Hinduism. It spread to my nearest neighbour, the Spanish, who adopted it as state religion. After most of the map and the other civs had been discovered, I noticed that Hinduism had spread to all Spanish cities except the one furthest away from me, Cordoba (which had adopted Buddhism from a third party). I had even planted Hinduism in some cities beloning a third civ on the other side of the Spanish.

So, Cordoba was completely surrounded by Hinduist cities, every other Spanish city was Hindust and Hinduism was also their state religion. Still, the city never adopted Hinduism. I didn't bother with missionaries, because I was sure the city would adopt it any turn, as overwhelming as the surrounding pressure of Hinduism seemed, but it never did. I got the impression that the game rolled a die when the Hinduist influence had reached Cordoba: Will Cordoba adopt Hinduism? The result was no, and then the game never rolled the die again. :confused:

In other words: Will a city (without theocracy) eventually adopt a neighbouring religion through the sheer grind of time, or will it never adopt a religion once it has "rejected" it? Also, what are the modifiers if a city already has a religion, or two religions, or three, and so on? Or is a missionary the only way to spread a religion if it already has another one?

Thankful for answers. :king:
 
1. What exactly is the "influence" on the religious advisor's screen? Is it only affected by the number of cities with the religion and the size of these cities? Or also whether other civs have it as state religion, and how powerful those civs are? Do monastaries, temples and cathedrals in your cities boost the "influence" by boosting the culture your religion generates?
AFAIK it is the % of cities with that religion compared to all cities

2. Is a trade network connection by roads/rivers/coastlines absolutely necessary for the spread of religion, or does it only affect the speed of the spread?
No - you can even make contact with another civ on another continent prior to Astronomy if sheer luck spreads your state religion to one of their cities and you gain Line of Sight... It does affect the speed of religion spreading though...

3. If I'm the founder of a religion, it seems to spread to my own cities fairly quickly. Is the spread slower between the cities of non-founding civilizations (assuming that none of those civs' cities have any religion at all), even if they are as well connected as my own cities, and at same distance (number of tiles) from the holy city?
not sure about this - but open borders and trade routes do affect the spread rate - there might be a modifier for state religion which I cannot find in the SDK... also connection to the Holy city or even shrine increases spread rate...

4. If you count aside missionaries, does a religion ONLY spread from the holy city and outwards, or from any city with the religion? I have sent missionaries to far away cities of other civs, but does the religion spread on from there to adjacent connected cities? In other words, can you with a missionary spread religion in a single city on another continent, and then watch it sprawl across the entire continent eventually (during a considerable time, but still), without any other active measures on your behalf? I have never noticed that this works myself.
I *think* it only spreads from the holy city - but as noted above it can spread without established connection...

5. Does the spread of religion slow down or stop to halt after a certain technology or civic? After a certain distance from the holy city? I get the impression that when I reach the medieval times or so, my religion doesn't seem to spread outwards any more.
6. The manual says that "some religious buildings increase the speed at which a religion will spread", but it's not very clear how, except by the creation of missionaries. How does this work? Do monastaries, temples and cathedrals actually speed up the spread? If so, are they more important in border cities than in core cities?
Religion spread does not decrease with time. But the rate has a plot distance modifier so it is easier to spread to nearer cities. AFAIK only the shrine will increase spread rate (and monastries allow for missionaries of course...)

7. Related question: Does your cultural output (i.e. your cultural superiority/inferiority compared to your neighbouring civs) - by religious buildings or otherwise - affect how fast your religion spread to your neighbours? In other words, are they more likely to adopt your faith if they are awed by you?
There is a modifier ReligionInfluence in the spread rate but I cannot find where it is derived from (I am pretty sure it is not the influence you see in the Religious Advisor screen)

8. How does the mechanism for whether a city will adopt the religion work?

In a recent game I founded Hinduism. It spread to my nearest neighbour, the Spanish, who adopted it as state religion. After most of the map and the other civs had been discovered, I noticed that Hinduism had spread to all Spanish cities except the one furthest away from me, Cordoba (which had adopted Buddhism from a third party). I had even planted Hinduism in some cities beloning a third civ on the other side of the Spanish.

So, Cordoba was completely surrounded by Hinduist cities, every other Spanish city was Hindust and Hinduism was also their state religion. Still, the city never adopted Hinduism. I didn't bother with missionaries, because I was sure the city would adopt it any turn, as overwhelming as the surrounding pressure of Hinduism seemed, but it never did. I got the impression that the game rolled a die when the Hinduist influence had reached Cordoba: Will Cordoba adopt Hinduism? The result was no, and then the game never rolled the die again. :confused:

In other words: Will a city (without theocracy) eventually adopt a neighbouring religion through the sheer grind of time, or will it never adopt a religion once it has "rejected" it? Also, what are the modifiers if a city already has a religion, or two religions, or three, and so on? Or is a missionary the only way to spread a religion if it already has another one?

Thankful for answers. :king:
A religion will only spread without a missionary to city that is not barbarian and has no religion - this also explains the lack of spread you see later in the game - there should not be alot of cities without religion at that time...
 
A religion will only spread without a missionary to city that is not barbarian and has no religion - this also explains the lack of spread you see later in the game - there should not be alot of cities without religion at that time...

That means the AI often builds missionaries and actively spreads his/her religion, since there is a lot of cities with more than one religion...
 
I'm no expert here, but I thought religion spread from all cities with that religion, not just the holy city. I have had turns where two or three cities gained a single religion simultaneously, and I figured that was from multiple cities spreading to that city.

I have only noted religion spreading along trade routes, although I can't source code to back that up.


On question 6., the manual is referring to the shrines built by Great Prophets, which have "spreads this religion" in the description. As far as I know, building temples, monasteries, or cathedrals have no effect, or if they do, it doesn't matter where they are placed. That being said, I always put cathedrals in border cities given the option for the culture boost to grab tiles from neighbors...so I don't have any experience doing things any other way.
 
Glad you started this thread, because as a relative necomer to Civ 4, this has got to be one of the vaguest things I've seen in my many years of Civ playing. I'm still trying to figure this out, myself.

If I don't see a fairly regular new adoption by one of my cities, or a have a outlying city, I currently just build some missionaries. Basically, if I think chances are seeming pretty slim that my state religion will be spreading there anytime fast. So, I do this often.

I can't understand why they couldn't have some sort of explicit explanation of how this works. Rather than everyone wondering exactly what to do.

Theres's got to be a way to figure it out. In my other main game that I've played for years, Diablo 2, people have figured out the inner workings of every single thing you can imagine.
 
The above posts explain much of the mechanism of the spread of religion, but fail to mention that (at least in my experience) it spreads very, very slowly unless Missionaries are used. And which religion is spread without Missionaries seems random, unaffected by the influence of a dominant faith - in my current game Judaism had 43% influence and Christianity only 2% (it was present in only its founding city) when I first made contact with Isabella, but it was Christianity that spread into one of her cities, before I could get a Jewish Missionary there, and was promptly adopted by her as her State Religion. Isabella being Isabella, she immediately changed to Theocracy and took strongly against everybody else on the grounds of "heathen faith".
 
I can't understand why they couldn't have some sort of explicit explanation of how this works. Rather than everyone wondering exactly what to do.

Theres's got to be a way to figure it out. In my other main game that I've played for years, Diablo 2, people have figured out the inner workings of every single thing you can imagine.
Well the civopedia and the manual are crap for almost everything concerning game mechanics so I am not really surprised that it is the same for religion :shake:

However there is a simple way to find out how religion spread works - comb through the SDK - I actually did that for a couple of things and even though it is not annotated it is pretty simple to read. But I am confused by the religion stuff in there - All I can find concerning the spread of religion is the doReligion stuff in CvCity.cpp but it does not seem to govern all things I have seen in the games I played. But here it is:
Spoiler DoReligion from CvCity.cpp :

Code:
 [FONT=Arial]void CvCity::doReligion()[/FONT]
  [FONT=Arial]{[/FONT]
  [FONT=Arial]                CvCity* pLoopCity;[/FONT]
  [FONT=Arial]                int iRandThreshold;[/FONT]
  [FONT=Arial]                int iSpread;[/FONT]
  [FONT=Arial]                int iLoop;[/FONT]
  [FONT=Arial]                int iI, iJ;[/FONT]
  
  [FONT=Arial]                CyCity* pyCity = new CyCity(this);[/FONT]
  [FONT=Arial]                CyArgsList argsList;[/FONT]
  [FONT=Arial]                argsList.add(gDLL->getPythonIFace()->makePythonObject(pyCity)); // pass in city class[/FONT]
  [FONT=Arial]                long lResult=0;[/FONT]
  [FONT=Arial]                gDLL->getPythonIFace()->callFunction(PYGameModule, "doReligion", argsList.makeFunctionArgs(), &lResult);[/FONT]
  [FONT=Arial]                delete pyCity;          // python fxn must not hold on to this pointer [/FONT]
  [FONT=Arial]                if (lResult == 1)[/FONT]
  [FONT=Arial]                {[/FONT]
  [FONT=Arial]                               return;[/FONT]
  [FONT=Arial]                }[/FONT]
  
  [FONT=Arial]                if (getReligionCount() == 0)[/FONT]
  [FONT=Arial]                {[/FONT]
  [FONT=Arial]                               for (iI = 0; iI < GC.getNumReligionInfos(); iI++)[/FONT]
  [FONT=Arial]                               {[/FONT]
  [FONT=Arial]                                               if (!isHasReligion((ReligionTypes)iI))[/FONT]
  [FONT=Arial]                                               {[/FONT]
  [FONT=Arial]                                                               if ((iI == GET_PLAYER(getOwnerINLINE()).getStateReligion()) || !(GET_PLAYER(getOwnerINLINE()).isNoNonStateReligionSpread()))[/FONT]
  [FONT=Arial]                                                               {[/FONT]
  [FONT=Arial]                                                                              iRandThreshold = 0;[/FONT]
  
  [FONT=Arial]                                                                              for (iJ = 0; iJ < MAX_PLAYERS; iJ++)[/FONT]
  [FONT=Arial]                                                                              {[/FONT]
  [FONT=Arial]                                                                                              if (GET_PLAYER((PlayerTypes)iJ).isAlive())[/FONT]
  [FONT=Arial]                                                                                              {[/FONT]
  [FONT=Arial]                                                                                                              for (pLoopCity = GET_PLAYER((PlayerTypes)iJ).firstCity(&iLoop); pLoopCity != NULL; pLoopCity = GET_PLAYER((PlayerTypes)iJ).nextCity(&iLoop))[/FONT]
  [FONT=Arial]                                                                                                              {[/FONT]
  [FONT=Arial]                                                                                                                             if (pLoopCity->isConnectedTo(this))[/FONT]
  [FONT=Arial]                                                                                                                             {[/FONT]
  [FONT=Arial]                                                                                                                                             iSpread = pLoopCity->getReligionInfluence((ReligionTypes)iI);[/FONT]
  
  [FONT=Arial]                                                                                                                                             iSpread *= GC.getReligionInfo((ReligionTypes)iI).getSpreadFactor();[/FONT]
  
  [FONT=Arial]                                                                                                                                             if (iSpread > 0)[/FONT]
  [FONT=Arial]                                                                                                                                             {[/FONT]
  [FONT=Arial]                                                                                                                                                             iSpread /= max(1, (((GC.getDefineINT("RELIGION_SPREAD_DISTANCE_DIVISOR") * plotDistance(getX_INLINE(), getY_INLINE(), pLoopCity->getX_INLINE(), pLoopCity->getY_INLINE())) / GC.getMapINLINE().maxPlotDistance()) - 5));[/FONT]
  
  [FONT=Arial]                                                                                                                                                             //iSpread /= (getReligionCount() + 1);[/FONT]
  
  [FONT=Arial]                                                                                                                                                             iRandThreshold = max(iRandThreshold, iSpread);[/FONT]
  [FONT=Arial]                                                                                                                                             }[/FONT]
  [FONT=Arial]                                                                                                                             }[/FONT]
  [FONT=Arial]                                                                                                              }[/FONT]
  [FONT=Arial]                                                                                              }[/FONT]
  [FONT=Arial]                                                                              }[/FONT]
  
  [FONT=Arial]                                                                              if (GC.getGameINLINE().getSorenRandNum(GC.getDefineINT("RELIGION_SPREAD_RAND"), "Religion Spread") < iRandThreshold)[/FONT]
  [FONT=Arial]                                                                              {[/FONT]
  [FONT=Arial]                                                                                              setHasReligion(((ReligionTypes)iI), true, true);[/FONT]
  [FONT=Arial]break;[/FONT]
  [FONT=Arial]                                                                              }[/FONT]
  [FONT=Arial]                                                               }[/FONT]
  [FONT=Arial]                                               }[/FONT]
  [FONT=Arial]                               }[/FONT]
  [FONT=Arial]                }[/FONT]
  [FONT=Arial]}[/FONT]

If this is all there is to religion spread (and I doubt that) then religion spread is only determined by:
RandomNumber
Is City connected to City with religion (Holy City?) ?
Distance from that city
Spread rate (which is determined for each religion in the .xml files but is the same for all in the retail versions (mods can differ of course) and is modified by shrines)

Also spread is prohibited if in Theocracy and not the state religion or if another religion is present in that city...
All of this is calculated each turn.
 
I'm already glad to find out about that part about your state religion not spreading to one of your cities if another religion is present. I've already seen many of my cities with 2 or 3 religions, and I did not know that. That's ridiculous, that something as simple as this couldn't be explained somewhere.

I just might have to start building more shrines, I guess. Although missionaries are cheaper, and shrines expire, if I recall correctly.
 
Ah, thanks for the answers ori, and everyone else. I didn't know that it was IMPOSSIBLE for a religion to automatically spread (without missionaries) to a city that already has a different religion - it doesn't say anything in the manual. But it does explain a lot. :)
 
Although missionaries are cheaper, and shrines expire, if I recall correctly.
Shrines are the buildings that you can build only in the religion's holy city and only by using a great prophet - they do not expire and bring one gold per city with that religion so they are always worthwhile...
 
Shrines are the buildings that you can build only in the religion's holy city and only by using a great prophet - they do not expire and bring one gold per city with that religion so they are always worthwhile...


I know one of them expires. Couldn't remember, without checking. Monastary, perhaps?
 
I know one of them expires. Couldn't remember, without checking. Monastary, perhaps?

Monasteries do expire, but ori was talking about shrines, which don't. Shrines are the special buildings (one for each religion) that can only built in the Holy City of that religion

On the spread of religions: I was under the impresion that they mostly spread along the trade routes of your cities. Thus, connecting your cities to your trade netwrk should make it easier for them to adopt a religion. Also, Open Border agreements should help spreading your religion to other civs, because with open borders, your cities can have trade routes with foreign cities. Third, it is imperative to spread your religion fast. The first religion to spread in any area can easily experience a snowball effect: Since there is no other religion, the new religion spreads without any further efforts relatively fast to other cities. Once most cities already have a religion, you have to build lots of missionaries to achieve a similar effect.
 
On the spread of religions: I was under the impresion that they mostly spread along the trade routes of your cities. Thus, connecting your cities to your trade netwrk should make it easier for them to adopt a religion. Also, Open Border agreements should help spreading your religion to other civs, because with open borders, your cities can have trade routes with foreign cities. Third, it is imperative to spread your religion fast. The first religion to spread in any area can easily experience a snowball effect: Since there is no other religion, the new religion spreads without any further efforts relatively fast to other cities. Once most cities already have a religion, you have to build lots of missionaries to achieve a similar effect.

That's the reason why the later religions tend not to spread as quickly, or at all. Unless you have a religiously inclined leader like Isabella, you probably are not going to see the later religions game a massive foothold except in the strangest of cases.
 
Religion won't spread to a civ not connected to the trade network.
I played on the "Maze" map type setting a few times - it was really interesting. One game, a multiplayer with my husband, was set to 2 tiles wide, so every city was on a coast. One section of the maze - the part where I was located - was isolated from the other civs. I was too slow to found any of the religions, and I never got any until my husband specifically sent a missionary to me. It took a long time as he couldn't use a boat due to the shape of the map, and the missionary had to walk a long long way to find me. My cities were pretty much crippled due to unhappiness - there wasn't anything to build to make them happier.
Amy
 
I don't think "trade network" is precisely correct. I have had religions spread to civs I didn't know existed, and I am pretty sure you have to have open borders to be considered part of the trade network. But cities do need to be connected, even if their respective civs cannot trade.

Also, I have encountered barbarian cities that have religion. I only started noticing this recently, though, so it might be due to patch 1.61.
 
I don't think "trade network" is precisely correct. I have had religions spread to civs I didn't know existed, and I am pretty sure you have to have open borders to be considered part of the trade network.

That's true. However, you can have trade with cities you've never seen or heard about. This is because once you get Open Borders with another civ, all cities in your trade network will trade with all cities in their trade network, no matter whether or not you actually know the city.

Also, religion does not only spread from your cities, but also from other civ's cities that adopted your religion. So if you have Open Borders with Civ A, and A has Open Borders with B, and both A and B have many cities without a religion, then your religion will spread into B's cities even though you never heard about B and don't have Open Borders with him. (You will notice him as soon as his first city adopts your religion though).

That, however, does not explain the occasional spread of a religion to another continent way before sea trade has been invented. I think that was a bug that has been fixed in one of the patches, but I'm not sure.
 
I'm already glad to find out about that part about your state religion not spreading to one of your cities if another religion is present. I've already seen many of my cities with 2 or 3 religions, and I did not know that. That's ridiculous, that something as simple as this couldn't be explained somewhere.

I didn't know that either, but now that I do, I think that one way of making the 4 later religions more significant, is by allowing them to DO spread in cities that already have one (but not two or more) other religion, however more slowly than to cities with no religion.

It would allow for a more dynamic game, I think, because the civs who missed out on the early religions will have a change to gain a foothold too, and so the political allegiances might change drastically from the early game to the late. As it is now, civs very rarely seem to change their early game religion (without active measures from you).

It would also make theocracy stronger, for example if one of your neighbours founded a new religion which threatened to spread to the rest of the world via YOUR civ. Now, I mainly use Theocracy for the +xp bonus, because AI civs don't seem to bother with missionaries, so the spread to your cities is insignifant anyway.
 
The AI does use missionaries, at least some times. I've seen it in many games.
Recently, I had one send a Christian missionary to one of my cities. I might not have known, but they passed by one of my units to get to my city, and I happened to see it. Otherwise I might have thought the religion spread 'naturally' to that city, even though there was already at least one religion there.
I wish, when the message pops up 'X religion has spread to Y city' (or whatever it is) that it would say 'A missionary has spread X religion to Y city' if in fact it was from a missionary, and not just the natural spread of the religion. I'd like to know. It might even be nice if it said who sent the missionary.
Amy
 
The AI does use missionaries, at least some times. I've seen it in many games.
Recently, I had one send a Christian missionary to one of my cities. I might not have known, but they passed by one of my units to get to my city, and I happened to see it. Otherwise I might have thought the religion spread 'naturally' to that city, even though there was already at least one religion there.

They might do, but I haven't seen any myself, and I'm certainly not aware of AIs planting religion in MY cities (I only play on prince difficulty, maybe they're not used much by the AI on that level?)
 
They might do, but I haven't seen any myself, and I'm certainly not aware of AIs planting religion in MY cities (I only play on prince difficulty, maybe they're not used much by the AI on that level?)

They are more aggressive in spreading their religion on higher levels and also only the founder of an religion will bother to come after you with missionaries ;) - But even on Prince - if you have peaceful relations with a religion founder AND not have too many religions in your cities they will eventually send missionaries and ask you to convert lateron. I think they don't bother if you already have more than 3 or so religions in most cities, but I do not know that for sure...
 
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