AI and Difficulty

The difficulty in the Community Patch is unchanged, but the rest of Vox Populi changes difficulty greatly, as described below.

If you're interested in modifying these values for your own game, see the guide on Customizing Difficulty Levels.

The information listed below is accurate as of the 8-23 (August 23, 2020) hotfixed beta version.

Difficulty Level Edit

General Bonuses Edit

Additional Settler Bonuses Edit

AI Bonuses Edit

Additional Informations in DifficultyMod.xml Edit

AI Periodic Yield Bonuses Edit

When playing on difficulty levels higher than Settler, the AI receives bonus yields periodically upon triggering certain events, in an effort to match increasingly skilled human players. These bonus yields scale exponentially with era, beginning in the Medieval Era, and are much higher in later eras. Successful AI players will tend to trigger yield bonuses more often and as a result become more difficult opponents for others to take on.

An AI civilization receives bonus yields when it achieves any of the following:

• Enters a new era (3x normal bonus; Food, Production, Gold, Golden Age Points, Science, Culture)
• Founds its original capital (Gold, Golden Age Points)
• Founds a new city, other than its capital (Food, Production, Gold, Golden Age Points, Science, Culture)
• Wins a war (warscore 25+) (Food, Production, Gold, Golden Age Points, Science, Culture)
• Starts a Golden Age (Food, Production, Gold, Science, Culture)
• Constructs a World Wonder (Gold, Golden Age Points)
• Generates a Great Person (Gold, Golden Age Points)
• Completes an antiquity site dig by building a Landmark or extracting an artifact (Gold)
• Completes a trade route to another civilization or City-State (Gold)

The types of yields received by the AI differ based on the trigger for the event, and are listed above. Bonus Gold, Golden Age Points, Science and Culture yields are applied once at the empire level, whereas bonus Food and Production yields are divided equally between the cities in the AI's empire.

The specific amount of yields received is based on the formula below, with the following outside variables:

• iEra is the average era among all major civilizations^[9]. It is 1 in Ancient/Classical, 2 in Medieval, 3 in Renaissance and so on.
• iHandicapBase, iHandicapA, iHandicapB, and iHandicapC are defined in the DifficultyMod.xml file, and are listed above. iHandicapBase is effectively a multiplier on the total number of yields received.
• TrainPercent is 67 on Quick speed, 100 on Standard, 150 on Epic, and 300 on Marathon.

Finally the formula:

void CvPlayer::DoDifficultyBonus(HistoricEventTypes eHistoricEvent)
{
	int iEra = GC.getGame().getCurrentEra();
	if (iEra <= 0)
	{
		iEra = 1;
	}
	int iHandicapBase = 0;
	int iHandicapA = 0;
	int iHandicapB = 0;
	int iHandicapC = 0;
	int iYieldHandicap = 0;

	CvString strLogString;

	CvHandicapInfo* pHandicapInfo = GC.getHandicapInfo(GC.getGame().getHandicapType());
	if (pHandicapInfo)
	{
		iHandicapBase = pHandicapInfo->getAIDifficultyBonusBase();
		iHandicapA = pHandicapInfo->getAIDifficultyBonusEarly();
		iHandicapB = pHandicapInfo->getAIDifficultyBonusMid();
		iHandicapC = pHandicapInfo->getAIDifficultyBonusLate();
		iYieldHandicap = iHandicapBase * ((iHandicapC * iEra * iEra) + (iHandicapB * iEra) + iHandicapA) / 100;

		iYieldHandicap *= GC.getGame().getGameSpeedInfo().getInstantYieldPercent();
		iYieldHandicap /= 100;
	}
	int iYieldForCities = max(1, iYieldHandicap / max(1, getNumCities()));
	if (iYieldHandicap > 0)
	{
		switch (eHistoricEvent)
		{
			case HISTORIC_EVENT_ERA:
			{
				iYieldHandicap *= 3;
				int iLoop;
				for (CvCity* pLoopCity = firstCity(&iLoop); pLoopCity != NULL; pLoopCity = nextCity(&iLoop))
				{
					if (pLoopCity != NULL)
					{
						pLoopCity->changeFood(iYieldForCities);
						pLoopCity->changeProduction(iYieldForCities);
					}
				}
				GetTreasury()->ChangeGold(iYieldHandicap);
				ChangeGoldenAgeProgressMeter(iYieldHandicap);
				changeJONSCulture(iYieldHandicap);

				TechTypes eCurrentTech = GetPlayerTechs()->GetCurrentResearch();
				if (eCurrentTech == NO_TECH)
				{
					changeOverflowResearch(iYieldHandicap);
				}
				else
				{
					GET_TEAM(getTeam()).GetTeamTechs()->ChangeResearchProgress(eCurrentTech, iYieldHandicap, GetID());
				}
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: ERA - Received Handicap Bonus (%d in Yields): FOOD, PRODUCTION, GOLD, GAP, CULTURE, SCIENCE.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_WONDER:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				ChangeGoldenAgeProgressMeter(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: WONDER - Received Handicap Bonus (%d in Yields): GOLD, GAP.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_GP:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				ChangeGoldenAgeProgressMeter(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: GREAT PERSON - Received Handicap Bonus (%d in Yields): GOLD, GAP", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_WAR:
			{
				int iLoop;
				for (CvCity* pLoopCity = firstCity(&iLoop); pLoopCity != NULL; pLoopCity = nextCity(&iLoop))
				{
					if (pLoopCity != NULL)
					{
						pLoopCity->changeFood(iYieldForCities);
						pLoopCity->changeProduction(iYieldForCities);
					}
				}
				GetTreasury()->ChangeGold(iYieldHandicap);
				ChangeGoldenAgeProgressMeter(iYieldHandicap);
				changeJONSCulture(iYieldHandicap);

				TechTypes eCurrentTech = GetPlayerTechs()->GetCurrentResearch();
				if (eCurrentTech == NO_TECH)
				{
					changeOverflowResearch(iYieldHandicap);
				}
				else
				{
					GET_TEAM(getTeam()).GetTeamTechs()->ChangeResearchProgress(eCurrentTech, iYieldHandicap, GetID());
				}
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: WAR - Received Handicap Bonus (%d in Yields): FOOD, PRODUCTION, GOLD, GAP, CULTURE, SCIENCE.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_GA:
			{
				int iLoop;
				for (CvCity* pLoopCity = firstCity(&iLoop); pLoopCity != NULL; pLoopCity = nextCity(&iLoop))
				{
					if (pLoopCity != NULL)
					{
						pLoopCity->changeFood(iYieldForCities);
						pLoopCity->changeProduction(iYieldForCities);
					}
				}
				GetTreasury()->ChangeGold(iYieldHandicap);
				changeJONSCulture(iYieldHandicap);

				TechTypes eCurrentTech = GetPlayerTechs()->GetCurrentResearch();
				if (eCurrentTech == NO_TECH)
				{
					changeOverflowResearch(iYieldHandicap);
				}
				else
				{
					GET_TEAM(getTeam()).GetTeamTechs()->ChangeResearchProgress(eCurrentTech, iYieldHandicap, GetID());
				}
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: GOLDEN AGE - Received Handicap Bonus (%d in Yields): FOOD, PRODUCTION, GOLD, CULTURE, SCIENCE.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_DIG:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: DIG - Received Handicap Bonus (%d in Yields): GOLD.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_TRADE_CS:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: TRADE (CITY-STATE) - Received Handicap Bonus (%d in Yields): GOLD.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_TRADE_LAND:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: TRADE (LAND) - Received Handicap Bonus (%d in Yields): GOLD.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_TRADE_SEA:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: TRADE (SEA) - Received Handicap Bonus (%d in Yields): GOLD.", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_CITY_FOUND_CAPITAL:
			{
				GetTreasury()->ChangeGold(iYieldHandicap);
				ChangeGoldenAgeProgressMeter(iYieldHandicap);
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: FOUND CAPITAL - Received Handicap Bonus (%d in Yields): FOOD, PRODUCTION, GOLD, GAP", iYieldHandicap);
				break;
			}
			case HISTORIC_EVENT_CITY_FOUND:
			{
				int iLoop;
				for (CvCity* pLoopCity = firstCity(&iLoop); pLoopCity != NULL; pLoopCity = nextCity(&iLoop))
				{
					if (pLoopCity != NULL)
					{
						pLoopCity->changeFood(iYieldForCities);
						pLoopCity->changeProduction(iYieldForCities);
					}
				}
				GetTreasury()->ChangeGold(iYieldHandicap);
				ChangeGoldenAgeProgressMeter(iYieldHandicap);
				changeJONSCulture(iYieldHandicap);

				TechTypes eCurrentTech = GetPlayerTechs()->GetCurrentResearch();
				if (eCurrentTech == NO_TECH)
				{
					changeOverflowResearch(iYieldHandicap);
				}
				else
				{
					GET_TEAM(getTeam()).GetTeamTechs()->ChangeResearchProgress(eCurrentTech, iYieldHandicap, GetID());
				}
				strLogString.Format("CBP AI DIFFICULTY BONUS FROM HISTORIC EVENT: FOUND CITY - Received Handicap Bonus (%d in Yields): FOOD, PRODUCTION, GOLD, GAP, CULTURE, SCIENCE.", iYieldHandicap);
				break;
			}
		}
	}

	if (GC.getLogging() && GC.getAILogging())
	{
		CvString strTemp;

		CvString strFileName = "DifficultyHandicapLog.csv";
		FILogFile* pLog;
		pLog = LOGFILEMGR.GetLog(strFileName, FILogFile::kDontTimeStamp);

		CvString strPlayerName;
		strPlayerName = getCivilizationShortDescription();
		strTemp += strPlayerName;
		strTemp += ", ";

		CvString strTurn;

		strTurn.Format("%d, ", GC.getGame().getGameTurn()); // turn
		strTemp += strTurn;

		strTemp += strLogString;

		pLog->Msg(strTemp);
	}
}

Notes Edit

1. ↑ Players with lower StartingLocPercent values are placed on the map before players with higher values (somewhat increasing the odds of obtaining a favorable starting position). If two or more players have the same StartingLocPercent value, the order of placement is determined randomly. Civilizations are always placed on the map before City-States, since the StartingLocPercent value for City-States is multiplied by 10.
2. ↑ If the game starts in a later era (e.g. Industrial rather than Ancient), an additional 2 base unit supply is added per era, beginning in the Classical Era.
3. ↑ Puppet cities only contribute half of their total population towards this percentage, unless you're playing as Venice.
4. ↑ ^{4.0 4.1} This is measured in approximate pathfinder turns (i.e. a range of 3 means a Barbarian unit will search for visible targets that it can reach within 3 turns of movement.)
5. ↑ This is the maximum bonus when fighting in the enemy's territory. In neutral territory, the maximum CS/RCS bonus is reduced by half (rounded down). In owned territory, the bonus does not apply. The bonus begins at 0, is raised by the player's warmongering behavior (declaring war and capturing cities), and decays over time.
6. ↑ The AI receives 33% less XP on Quick, 50% more XP on Epic, and 200% more XP on Marathon. These multipliers are also used for the AI's periodic yield bonuses.
7. ↑ AI units that gain XP from revealing tiles (i.e. scouts) do not receive the sight bonus.
8. ↑ While most per-era scaling in Vox Populi counts the Ancient and Classical Era as one era, the AIPerEraModifier does not, and its discount is applied starting in the Classical Era.
9. ↑ Calculated by adding the era number of each major civ team together, then dividing by the number of major civ teams and rounding down.