Here is some information on barbarians. Noone have seen fit to make it into an article yet which is a shame, as such I figured I might as well paste in the relevant info here(things in italics i've added):
A lot is gotten from http://forums.civfanatics.com/showthread.php?t=299483 this thread.
On barb visbility:
Barb animals don't enter resources unless to attack an unit already there.
A lot is gotten from http://forums.civfanatics.com/showthread.php?t=299483 this thread.
Well, here is what I found digging through the 3.17 SDK (finally with a new Debug dll, yeah!):
Barbs enter cultural borders if an appropriate mission is chosen in CvUnitAI::AI_barbAttackMove(). This function is only called for barbarian units with UNITAI_ATTACK (barb animals always have UNITAI_ANIMAL and they cannot enter owned plots anyway). So this represents a direct effect of the difficulty level as non-animal barbs (Warriors and Archers) spawn earlier plus in greater numbers on the higher levels. The indirect effect is indeed given by the conditional behavior of the barb units depending on the total number of non-barb cities on the whole map (not continents! -- the continents(=areas) only determine their number of needed barbs according to their unowned tiles).
There are 2 thresholds:
A) NumCities > 2*NumPlayersAlive:
B) NumCities > 3*NumPlayersAlive:
- Barbs will enter your territory if they can pillage an improvement on their next turn, so the common 1
barb Warriors and Archers will intrude to pillage improvements in your border tiles. I'm not certain about 2
- Barbs will enter your territory if they can attack a city on the same turn --> this should only be possible for the uncommon 2
The restrictions for the missions are lifted to
With GAMEOPTION_RAGING_BARBARIANS it gets even worse (NumCities is irrelevant then):
- pillage on the 3rd turn
- attack city on the second turn
- If the barbs have calculated AREAAI_OFFENSIVE for their AreaAI (huge numbers of ATTACK barb units, most likely after random event; normally it's AREAAI_MASSING) they will straight target their chosen city without any such restrictions.
Important things to keep in mind:
- pillage on the 4th turn
- attack city on the 3rd turn
- target city when AREAAI_OFFENSIVE
- Barbs will ALWAYS enter your borders if they can attack one of your units directly (--> watch your Workers!).
- Once they have entered your territory, they will consider the following options for their current turn
- pillage an improvement (50%)
- attack somebody
- depending on conditions A and B move to another tile to pillage or attack a city (or target a city)
- patrol --> here they always prefer to move into unowned tiles (this is why they don't enter in the first place; if possible they will move out again; if they somehow get boxed in by cultural borders they might also "have to" enter your territory with this mission)
- Hence they can also change their minds - if they enter to pillage on their 3rd turn, they will choose to attack somebody on their second turn if possible (if you move a defending unit to an adjacent tile).
- There are certainly special situations where barb behavior might contradict the above rules (the code for unit AI is pretty complex...)
Barb units do not differ from other AI units in general, they also have a certain courage to attack. They just behave more erraticly and have lower inhibition thresholds on average.
The decision to attack a unit or not is made via a comparison of the unit's AttackOdds vs. a threshold individually specificied for all mission test calls (AI_anyAttack, AI_cityAttack). There are a lot of calculations adjusting the odds and thresholds depending on the situation of the combatants. What I read from all this is, that the AttackOdds are similar to the well known combat odds (depending on the strength, damage and bonuses of attacker and defender) + a "dare-devil offset", the AttackOddsChange. Each AI leader recalculates his/her AttackOddsChange each turn during CvPlayerAI::AI_doMilitary() according to:
[pre]AttackOddsChange = BaseAttackOddsChange + RNG(AttackOddsChangeRand) + RNG(AttackOddsChangeRand)[/pre]IIUC this value should vary around an average of BaseAttackOddsChange + AttackOddsChangeRand-1. As you can read from the Leaderhead-xml (or my converted spreadsheet) the barbs have BaseAttackOddsChange = 0 (it is 0 for Gandhi ... 6 for Ragnar), which would make them cowards, but their AttackOddsChangeRand = 16, that is double the value of all other leaders (8), so on average they should attack more often than Ragnar (0 + 15 > 6 + 7).
The great variation of the barbs' AttackOddsChange (0...30) is responsible for their erratic behavior -- they will often shy from combat on one turn and move pass your defenders only to attack them on the very next turn. As mentioned above the thresholds used in CvUnitAI::AI_barbAttackMove() are especially low (20, 15, 10), so that the barbs might attack regardless of the actual combat odds during certain turns, when a very high AttackOddsChange might bring them over the relevant threshold alone.
Oh yeah, and they of course have a very advanced radar to detect all your units, cities and improvements. SearchRange = (Range+1)*(BaseMovements+1), with Range being the other parameter passed in the mission test calls besides the thresholds --> a 1circlewith a diameter of 9 tiles at the minimum (Range = 1).
Edit: It's not a circle but a sqaure area of 9 x 9 tiles.
Have you ever wondered about the sudden "wave" of barb units storming towards your capital followed by surprisingly very calm periods? That's exactly when threshold B) has been passed (NumCities > 3*NumPlayers) and the barbs have calculated AREAAI_OFFENSIVE for your area. In contrast to the misleading comment in the code of CvTeamAI::AI_calculateAreaAIType ("// XXX does this ever happen?") this is almost guaranteed to happen in every game. If the barbs haven't founded a city on your landmass yet, they only need TWO attack units for that AreaAI.
The formula for this minimum number of offensive units is:
[pre]N = ((NumBarbPop+NumBarbCities+1)*20)/100 + 2[/pre]So once they have a few cities on your landmass they more or less leave you alone again, because the number of "needed" barbs per landmass is limited by the number of unowned tiles and the difficulty level.
But during this period of harassment, not even the finest [game] tacticsor the broadest creative-boosted cultural borders will protect you...
Correct = increased my knowledge while watching the barbs storm my improvement-less 100capital in a WBed test scenario and took a closer look at the code...
Only the total barbarian population on your landmass (NumBarbCities likewise). So with 3 barb cities on your continent size 4 each, the barbs need N = ((3*4+3+1)*20)/100 + 2 = 5 roaming attackers for AREAAI_OFFENSIVE (hmmm, actually not *that* many).
Barb Galleys use UNITAI_ATTACK_SEA and thus require their own AI function CvUnitAI::AI_barbAttackSeaMove(). Obviously, you won't find any AI_attackCity or AI_targetCity calls in there, as boats are only allowed to attack units outside cities. Also, there aren't any similar NumCities-thresholds implemented here and the AreaAI of their area (= water!) has no effect. So once they are around, they will check their valid options in the following order:
- flip a coin (50% chance) and -if lucky- check whether an improvement can be pillaged this turn (AI_pillageRange(iRange=1))
--> they will move onto Fishing Boats in adjacent tiles and pillage them
.- check whether an enemy unit can be attacked on this or on the next turn (AI_anyAttack(iRange=2, iOddsThreshold=25))
--> they will target your Work Boats 4 tiles away; this can be exploited to keep them away from your improvements by some nice disco-fox dancing
.- check whether an improvement can be pillaged within 4 turns ((AI_pillageRange(iRange=4))
--> they will use their advanced AI radar to spot your improvements 7 tiles away, however, this radar can only detect improvements in the fog, if they exist for more than 20 turns (improved knowledge!, 5 turns for land units and improvements on land); the closest improvement "wins" (max(pillageValue/pathTurns))
.- AI_heal()
.- AI_patrol()
--> move into a random adjacent tile (iValue = 1...10,000); prefer unowned tiles (+20,000) and tiles not adjacent to borders (+10,000); if movement points left, recalculate ALL options (if the patrol-move reveals a "fresh" improvement, that was hidden from the AI radar in the fog before, option 3 will now be enabled and the respective mission (AI_pillageRange(iRange=4)) will be pushed)
At what time will the game spawn barb Galleys?
- the era of barb animals must be over (NumCities >= 3/2*NumPlayers; GameTurns > Handicap.BarbarianCreationTurnsElapsed * GameSpeed.BarbPercent)
- the barbs must know Sailing
How do barbs acquire their techs?
- Their real research rate is almost guaranteed to be 0, since they aren't allowed to have a Palace (8 commerce) and thus suffer from high maintenance (but they don't lose units via STRIKE).
- So they merely receive the 1 free beaker everybody gets (BASE_RESEARCH_RATE) for their current research plus 3% (BARBARIAN_FREE_TECH_PERCENT) of the cost of a tech scaled by the percentage of players who know it for each technology each turn. Hence, if the majority of the players in the game knows Sailing, it won't be long until the first barb Galleys come visit your fishing grounds.
On barb visbility:
Barb Animals start appearing after game turn 5 (hard coded, independent of game speed). As mentioned earlier the game stops spawning them if both of the following two conditions are met:
- The average number of (non-barb) cities per player must be >= 1.5.
.- A certain number of game turns must have elapsed (depending on difficulty [iBarbarianCreationTurnsElapsed] and game speed [iBarbPercent], marathon is special with 400%).
So in a quick deity game animals are usually only created in just 1 IBT (5->6).
When the era of barb animals is over, the existing creatures are not eradicated in 1 major extinction event. Instead, the game kills off 1 animal per turn until they are all gone and will insert regular barb units (Warriors, Archers, ...) as they are "needed" during the next IBT (can be > 1 unit/turn!, ALL required units are created immediately).
Barb animals don't enter resources unless to attack an unit already there.
Roads/railroads aren't Improvements technically but Routes instead, they do have an AI_pillageValue > 0 which is required to trigger the AI_pillageRange mission.
So barbs will enter borders to pillage if there are roads nearby.
A quick tip on fogbusting:
I'm not sure how many of you fellow civfanatics know about the GlobalDefines value MIN_BARBARIAN_STARTING_DISTANCE = 2 and already exploit it. It means that new barbarian units are not allowed to spawn within a 2 tile radius of ANY existing unit (including other barb units) on the map. This rule allows very efficient "fogbusting" on smaller landmasses. Here is an example (spoiler for current LHC Huayna Capac checkpoint 1):
Spoiler :
2 Quechuas and 1 Scout are all I need to keep my lands barb-free. It is not required to have active vision for all the tiles (the fog doesn't matter). I've changed the Dotmap-function of BUG to display the no-spawn areas for my three units.
Note that barb cities CAN appear 2 tiles away from my units if the tile is in the fog though.
So basically the range around a unit is just a BFC but with the corners as well? Does this count for barb galleys as well?
Yeah, maybe we call it BFS = big fat square or barb f....forbidding square. The rule applies to the infamous barb galleys as well --> it's nice to barb-bust in barb galley breeding areas with those 1-tile offshore islands using work boats which can be sent into the fishing grounds later. As mentioned above, the barb units (warriors/archers) stationed in spawned barb cities do the same job.
Can a barb city spawn where a unit couldn't?
Although MIN_BARBARIAN_CITY_STARTING_DISTANCE = MIN_BARBARIAN_STARTING_DISTANCE = 2, the rules are different. Barb cities can definitely spawn in a units BFS as long as no non-barb player has active vision for that tile. (That's also why the AI sends there GUARD_CITY units out to the chosen city sites.) It has happened to me before.
Even though barbs can't appear at the very beging of the game can you still pop the from huts?
It's not possible if you haven't founded your capital yet or if the hut is at a PlotDistance < 8 tiles away from your capital. So if you move your settler and your warrior diagonally away in opposite directions and found your capital first on turn 1 to achieve a great enough distance, you can then pop barbs from a hut that early. (Try it with random seed in a deity WB-scenario.)
Even though the entire continent is within 2 squares of a unit, a city can still spawn in a single tile of fog?
Yes, I recommend actual fogbusting in the juicy areas with high founding values (lot's of resources, often coastal) where you plan to get a city up via a settler. It's interesting to note that the likelihood for an early barb city spawning on your LHC island is rather low -- the game prefers to spawn them on the continents with the highest number of owned tiles, even if these places are much crappier than the sites on your continent.
Any unit can spawnbust; Workers, Settlers, Missionaries, Spies, Great People ...
The city defenders will test the missions AI_leaveAttack() and AI_chokeDefend(); if one of those missions gets pushed they will leave the city to attack weak enough units in the vicinity of the city. AI_leaveAttack() exclusively checks the tiles adjacent to the city, but AI_chokeDefend() calls AI_anyAttack() during which movement on roads/railroads is also considered --> the defenders will even leave their culture to attack a unit 2 tiles away if they can reach it via road. However, it appears these checks are only performed in the case that AI_getPlotDanger() returns true for the city plot --> since non-military units like Workers and Settlers don't "cause danger" it might be wiser to let these units scurry past the barb cities unescortedbut I don't give any guarantees here ...
Oops, seems I was wrong about AREAAI_ASSAULT_MASSING -- that AreaAIType is not used by the barbs.
I assumed the mechanics here were similar to the ones responsible for the progression from AREAAI_MASSING --> AREAAI_OFFENSIVE depending on the number and UnitAIs of the available units. But the units don't have an effect.
Regular AIs will calculate AREAAI_ASSAULT_MASSING in situations, where they are preparing for an intercontinental invasion (WARPLAN_PREPARING_TOTAL or WARPLAN_PREPARING_LIMITED). After the fixed turns of preparations are over they will switch to WARPLAN_TOTAL / WARPLAN_LIMITED and the corresponding AreaAIType AREAAI_ASSAULT. (There is no switching out of WHEOOHRN ala ALC#24-Saladin if the target is on another landmass.)
So the barbs just use AREAAI_ASSAULT if they are alone on an island.
The AreaAITypes have an effect on what the AIs choose to produce in their cities, and how they value and move their units (very complex). AREAAI_ASSAULT will let the barbs launch intercontinental raids Viking-style IF they can reach other civs' cities via Galleys. They are not allowed to build better transport ships (but they can build Privateers, Frigates and Paratroopers
