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Vocum Sineratio: Dona Eis Relions

Discussion in 'Civ4 Strategy Articles' started by VoiceOfUnreason, Aug 13, 2007.

  1. VoiceOfUnreason

    VoiceOfUnreason Deity

    Dec 5, 2005

    Dona Eis Religions

    Dost thou know the magnitude of thy sin before the gods?

    Religion Basics

    There are seven techs which each introduce a religion into the game. Each religion is introduced in a single city, but can spread throughout the world. Converting to a religion can provide bonus happy, more buildings to construct, diplomatic bonus (and penalties), and unlock powerful civics.

    The actual mechanics of the religion engine are not always clear, so questions are common, albeit less common than wrong answers. Hence, this effort to put all of the right answers in one place.

    Founding a Religion

    For games that begin in the Ancient Era, no civs begin the game with knowledge of any of the religious technologies. Therefore, each religion is first introduced to the game when the corresponding technology is discovered:

    Meditation Buddhism
    Polytheism Hinduism
    Organized Religion Judaism
    Code of Laws Confucianism
    Theology Christianity
    Philosophy Taoism
    Divine Right Islam

    In Beyond the Sword Choose Religions is a custom game option that removes the relationship between a technology and the religion specific to it. If you are the first to discover a religious technology, you may choose which religion you found (save only that you may not duplicate an existing religion). Some of the AI Leaders have a preferred religion as well (defined in CIV4LeaderHeadInfo.xml), and will select accordingly. Those leaders who do not have a preferred religion defined will default to the religion normally associated with the technology.​

    These religions are almost interchangeable - the strategic resource which accelerates the construction of a Cathedral is the only difference in the game mechanics.

    Note that there is are no tie breaker mechanics, because there are no ties. The religion is founded when you discover it (mid turn if you lightbulb the technology, between End Turn and the start of the next player's turn if you research the technology the old fashioned way).

    For games which start in later eras, all of the players in the game share knowledge of one or more religious technologies. These religions are distributed randomly at the beginning of turn 6 (defined in CvGame::doHolyCity). The selection process is biased in favor of human players, and in favor of spreading the religions out. Each of the religions is checked in the order listed in Civ4ReligionInfo.xml - so in single player play the human almost always founds Judaism.

    In Beyond the Sword, the bias in favor of the human player has been removed. Also, the turn clock is disabled if you are playing an Advanced Start custom game. Furthermore, your leader's preference takes precedence over your own, when the religions are being dealt out.​

    The Holy City

    Each religion in the game has a single Holy City, which has a special, unique relationship with that religion. In game terms, the holy city for a religion is permanent - raze the holy city, and it is not replaced; expect severe diplomatic penalties.

    The holy city is important in a number of respects - it generates more culture than a converted city, it is the source from which the religion magically spreads (see below), and it is the only city in which the Shrine for that religion can be built.

    The last of these is an important element of religion based strategies, as a consequence, the mystery of which city will be the source of the religion is an important one.

    One important point, often missed by those who prefer single player games, is that religious technologies, like every other technology in the game, are discovered by teams, not players. In other words, when "you" discover a technology, you may find that one of your Permanent Ally's cities is chosen has the holy seat. Which player lands the religion is determined by a random number added to the total number of religions in that player's cities, and a 10x multiplier that biases the result in favor of those members of the team who were actively researching the tech at the time.

    Once the player has been determined, that player's cities are each checked in turn. A random seed is added to the city's population, which then has two negative factors applied to it - an 8x bias against the city with the Palace, and a smaller bias scaled with the number of religions already present in the city.

    So while you cannot assign the holy city as you might wish, you can arrange circumstances so that the biases work in your favor (keep the population high, keep the population in other candidates low, refrain from spreading religions to your preferred city, aggressively convert the other cities).

    Spreading the Word

    After a religion has been founded, there are too vectors by which it may spread to another city.

    Spontaneous Conversion

    At the end of each player's turn, each of his cities is checked against each religion to see if the city will spontaneously convert to that religion. To be eligible, the city must be free of religions, and must be Trade Network Connected to the holy city.

    Very rarely, you will see the announcement that you have founded a religion, and immediately find that it has spread to other cities. This demonstrates the timing of the game mechanics; after you hit end turn, your research occurs, followed shortly thereafter by CvCity::doReligion. The technology splash screen appears after all of this, at the beginning of your subsequent turn. With truly unfortunate timing (and rather dubious prioritization), you could theoretically find that - having founded a religion - you have a converted city (immediate spread from the holy city) but ruins where your holy city may have briefly stood (were it razed by one of the opposing players.​

    Trade Network connected means almost what it sounds like; there must be a connection between the converted city and the holy city - that is, the cities must be part of the same plot group. Plot groups are determined by explicit routes (roads, railroads), and terrain routes (oceans, rivers, coastline). These latter types depend on which technologies have been discovered by the owner(s) of the cities. Why almost? Because cities can connect through a closed border.

    Two factors determine the probability that the city will convert, given that it is connected to the holy city.

    The first factor is plot distance, expressed as a percentage of the maximum possible plot distance on the map.

    Two different distance terms are used in CIV. Step distance treats diagonals as one unit of distance. Plot distance treats them as roughly 1.5. When you watch a city expand its cultural borders, you are seeing it expand using plot distance​

    In an unmodded game, you'll observe about 10% per turn if you are in the immediate neighborhood of the holy city, falling off to 0.1% at the furthest corners of the map.

    The second factor is the amount of influence the holy city has - the only building which affects the influence is the shrine, which doubles the probability that the religion will spread.

    Although all of the religions are checked each turn, the test is interrupted if the city converts, so you will only see one spontaneous conversion in a city. The religions are checked in order, so there's a probably-not-perceptible bias in favor of Judaism.


    Missionary Man, he's got God on his side...

    To deliberately spread a religion to a city, you may use a missionary to convert the city; this consumes the missionary. You can train the missionary in any city which has already converted to that religion if either of the following is true
    • The city has constructed a monastery
    • You are running the Organized Religion civic
    Once the missionary has been trained, you simply move him to the target city, and click the convert action icon.

    But... it doesn't always work. If a city already has a religion, there's some chance that the conversion will fail. The probability of failure increases linearly with the number of religions already in the city. You have better odds converting your own cities (about 9% chance of failure per previous religion), than those of other teams (the failure rate rises to almost 12% per).

    For your own cities, the true conversion rates are (100%, 91%, 82%, 74%, 65%, 57%, 48%). Hooray for integer math. Missionaries abroad have conversion rates (100%, 88%, 77%, 65%, 54%, 42%, 31%).

    Automated missionaries use a scoring algorithm to choose the city they will attempt to convert. Of some interest may be the fact that automated missionaries treat cities with no religions as though they had two religions for scoring purposes - therefore automated missionaries will prefer to convert cities with exactly one religion, all other things equal.


    Complicating things further, the Theocracy civic is documented to "prevent the spread of non-state religions. Once again, this doesn't quite mean what it says.

    For spontaneous spreading, this is precisely right; your state religion is allowed to flow to one of your unconverted cities (if it is connected to the holy city), but no other religions may do so.

    For missionary spreading, you prevent your opponents from spreading non-state religions to you, but you don't prevent your teammates from doing so. You can always spread the religion yourself with your own missionaries, and your opponents can use their missionaries to spread your own state religion to you.

    To be continued


    A strategy for consistent cultural wins on Monarch
    walkerjks dedicated a post to religious strategy​

    RB1 - Cuban Isolationists
    Sirian wakes the Hydra​

    Pilgrimage to Mecca
    DaveMcW's single screenshot response to Immaculate's challenge​
  2. VoiceOfUnreason

    VoiceOfUnreason Deity

    Dec 5, 2005
    When I have specific questions that need volunteer participation, I'll drop them in here.

    20070814: Would anybody care to verify that Monasteries continue to get wonder generated effects (bonus gold, research, hammers) even after the discovery of Scientific Method makes them "obsolete"?
  3. VoiceOfUnreason

    VoiceOfUnreason Deity

    Dec 5, 2005
    Ugh - too tired to continue, worried about losing the work. I think I've got all of the tricksy game mechanics covered. There's obviously a big strategy session to come, and the bibliography. I feel like I'm also missing a lot of the basics, so I need to go back and fill those in as well. This is probably about 1/3 of what I have planned for the first draft.
  4. Percy

    Percy Cow who laughs

    Feb 19, 2005
    Thanks a lot, i'll be waiting for the updates =P
  5. MrCynical

    MrCynical Deity

    Oct 30, 2005
    The Dreaming Spires
    I don't think this is correct, unless they've changed it in the most recent patch. Theocracy only blocks missionaries. It has no effect at all on spontaneous religion spread, so non-state religions may spread to a city with no religion, even if the civ is running theocracy.
  6. VoiceOfUnreason

    VoiceOfUnreason Deity

    Dec 5, 2005
    I'm confident that it has always been this way - for sure, it's been this way since I started looking at the question.

    CvCity::doReligion -- the die roll for conversion is guarded by a isNoNonStateReligionSpread test.
  7. marius312

    marius312 Prince

    Jan 8, 2007
    I suggest you change the title of this article - people miss out on this because they don't understand what it's about!
  8. Refar

    Refar Deity

    Apr 10, 2005
    I think you can't change the tittle of the thread once it is started.

    The bias is not that small... When playing Vanilla, i was allways wondering, why Judaism seemed to spread more than other religions. Back then i was thinking, that it might be just my imagination... Now reading this, i see it was not just imagined. For some reason i did not noticed the "judaism-spam" since i got BTS. I think it might be because playing "Choose religions" Judaism is not necessarily comes as early religion...

    Let say each religion has s chance to spread to the city in question.

    So Judaism - checked first has s. The second religion - Christianity (if founded already) - has s too, but only if judaism did not strike first, so its s * (1 - s)

    i.g. for the n-th religion the chance to spread is s*(1-s)^(n-1)

    let assume s = 0.05 ~ 5% chance to spread, for every religion.

    P_1 = 0.05
    P_2 = 0.0475
    P_3 = 0.0451
    P_4 = 0.0428
    P_5 = 0.0407
    P_6 = 0.0386
    P_7 = 0.0368

    The difference will be bigger at higher spread probability. The extreme example - close range + shrine - 20% - P_1 = 0.2, P_2 = 0.16, P_7 = 0.05
  9. Perugia

    Perugia Prince

    Jun 18, 2001
    Lancing, UK
    In a recent game 2 things happended that are relevant to this thread.

    In a recent Quecha rush game I was chasing down a Gandhi archer/archer/settler stack and they managed to found a city. My Quecha moved adjacent to the city.

    On Gandhi's turn Judaism was founded in the city and it immediately spread to a Russian city. I then attacked for the XPs before the archers could fully fortify and the city duly turned to ruins.

    The city was auto-razed as it was size 1 with no culture. Interestingly there was no diplomatic penalty in this case, I'm not sure exactly why there was no penalty but presume it was because it was hidden in the fog for the whole of its fleeting existance.
  10. KMadCandy

    KMadCandy giggling permanoob

    Oct 16, 2005
    they do not get the benefits after they're obsolete but the wonders are still active. apparently at that point, they're just buildings that give culture and happen to be able to build missionaries of the state religion flavor, but they're no longer affiliated with the state religion.

    one thing about BtS caught me off-guard. it's not spontaneous spreading, but i don't think it's quite fair either. there are random events and quest rewards in BtS that can spread your state religion to other cities, including cities belonging to another player, and including cities with a religion already (but i think only cities with just one religion). i asked a while back if anybody knew whether theocracy prevented that sort of spread, and a poster said that he was in theocracy and that he did get a non-state religion spread to his cities anyway, because of an event like that. i didn't see it myself obviously, and you know i can't read code to confirm it ;). i don't like it, but maybe that's working as intended. i figured it might be worth a mention, because some people use theocracy in BtS as insurance against the AP. between that and spies that can change your civics (altho i've never had the AI do that to me), there's absolutely no way to guarantee that non-state religions won't spread to you in BtS i guess.

    you automatically didn't get a penalty because it was auto-razed, so you had no choice. also, you only get the penalty from civs who have that religion as their state religion at the time of the razing, which likely was the case so you probably got a double-no-penalty.

    VOU: i got that from info ori in a thread earlier this year. here's the code if you want it. the thread was pre-BtS. please correct me if it's changed of course!
    by the way Perugia, cities get auto-razed if they never grew above size 1. you can set off 8 great works for tons of culture, but it still won't save a city that never grew. i tested that in BtS before posting to be sure it hadn't changed. in warlords, if it did grow to size 2 at some point, it wouldn't auto-raze even if it later went back down to size 1 and hasn't earned any culture. i wasn't patient enough to test that in BtS today to see if it has changed so i can't swear to it still. ;)
  11. Perugia

    Perugia Prince

    Jun 18, 2001
    Lancing, UK
    Thanks for your comments KMadCandy.
    Well that's a change from [civ3] that I wasn't aware of!
  12. Tecibbar

    Tecibbar unliving

    Sep 6, 2007
    Ur Sorry Ass

    What's the chance of auto spread if a city is half way between holy cities and end of the world, is it like 5%?
  13. Conquistador 63

    Conquistador 63 Deity

    Mar 30, 2006
    Great article. Is there a good one on the religious victory as well? I checked the War Academy and wasn't able to find it.
  14. Pikkis

    Pikkis Prince

    Jun 30, 2007
    Helsinki, Finland
    That was really great infomation! So, if I understood correctly, religious buildings of other faiths don't effect these rates at all?
  15. oldsaxon

    oldsaxon Warlord

    Oct 9, 2007
    When "you" discover a technology, you may find that one of your Permanent Ally's cities is chosen has the holy seat. Which player lands the religion is determined by a random number added to the total number of religions in that player's cities, and a 10x multiplier that biases the result in favor of those members of the team who were actively researching the tech at the time.

    Could you clarify this - is it better to have more religions, or fewer? Does it matter how widely they've been spread?
  16. magicalsushi

    magicalsushi Prince

    Aug 14, 2006
    Oxford, UK
    Now this is interesting. There are a couple of things here that are news to me. Firstly, that you need a connection to a religion's holy city to have it spread spontaneously, rather than just a connection to any city which has the religion. If a religion spreads from holy city A to city B, and then the connection between A and B is broken, then the religion will not be able to spread from B to other cities. I'd assumed that it would be able to. Maybe pillaging the roads around the holy city of the AP religion is worthwhile.

    The other thing was about probability of spontaneous spread. I've often seen people say on these forums that late religions have a higher chance of spontaneous spread than earlier ones, as compensation for arriving later. From what you've said, that's complete nonsense. It seems the only compensation they get is the free missionary. Earlier religions will get their shrines sooner, and later religions will have access to fewer 'virgin' cities with no religion. It seems late religions suck even more than I thought they did.

    As for the bias towards Judaism (and against Taoism), that seems pretty harsh to me - it may be small, but it's unnecessary. It probably wouldn't be too time-consuming to do the checks in a random order for each city (or even just rotate the order each turn). I usually end up with the two Chinese religions, which means I've unwittingly had a minuscule disadvantage in most of my games so far. ;)
  17. VoiceOfUnreason

    VoiceOfUnreason Deity

    Dec 5, 2005
    The logic (tucked away in CvTeam::setHasTech) will found the religion in a city of the player with the lowest "score". That starts with a random number in the range [10,20), +10 for each religion in some city (the spread doesn't matter at all), and then a x10 boost if that player was researching some other tech.

    So if you want the holy seats in your cities, push all of your religions to your teammate, and if you think you have the research in the bag, ask him to research something else.
  18. Badhron

    Badhron Warlord

    Jan 21, 2007
    The Great White North
    How is it that religions that I have founded can spread to other civs that I haven't met yet? I've played a few games were I found all religions before getting trade with anyone and convert to theocracy to prevent non state religions from getting out. This would effectively prevent the heathen religion modifier, but the non state religions still spread.
  19. VoiceOfUnreason

    VoiceOfUnreason Deity

    Dec 5, 2005
    Neither of those two mechanics work the way you think they do...

    Theocracy controls (for lack of a better term) the spread of religions to your cities, but does not change the mechanics of religious spread for other civs.

    Trade routes, and more generally open borders, aren't relevant. The key point is the existence of a trade NETWORK between the two cities. You can't shut down the trade network by closing your borders, or jumping to mercantilism, or any tricks like that.

    You can shut down the trade network by declaring wars (specifically, by declaring war on anyone network connected to your holy cities). In the age of Astronomy, that basically means "always war". However, even in an always war game, religions can leak if a network connection is established before you actually meet the opponent.

    The only real answer is to found your religions in a land locked city, not on a river, and with no roads leading to it. See Pilgrimage to Mecca (linked in the first post).
  20. r_rolo1

    r_rolo1 King of myself

    May 19, 2006
    Lisbon, Portugal
    I've a question... it's related with my article on isolation and the issue of religion spreading over assymetrical trade routes:
    Do trade network need to have a 2 way trade route possibility to be established? Or even only a one way trade route possibility does the job? And if it does, it does for both sides?

    P.S You know that Vocum sine ratio means " Voice without reason" and not " Voice of Unreason" ,don't you? ;)

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