Base defense response

How damage raises one house's anger at another, what each house's threat map records, and how a computer house calls armed infantry and vehicles back to defend.

Changed in 0.2.0

Damage to an object has two effects. It raises the anger the object’s owner holds toward the attacker’s house, and each house treats the house it is angriest at as its declared enemy. If a computer house owns the object, the hit can also start a call-up, which empties the house’s low-priority teams and sends armed infantry and vehicles back to fight the attacker.

Each house also keeps a threat map of where other houses’ objects stand, weighted by each type’s ThreatPosed. Damage does not change the map. The call-up is sized from the same ThreatPosed ratings, and the computer’s missiles, its teams and the pathfinder read the map.

The call-up works through teams. A team is a group of infantry, vehicles and aircraft that one house owns and that acts together. A TeamType is the scenario section a team is built from. AI triggers and team production introduces both. This page defines each TeamType setting it uses where that setting appears.

What counts as an attack

Two kinds of hit run the call-up: any hit on a structure, and an ordinary hit on a ToProtect=yes object. Both pass the call-up the object that caused the damage.

Damage to a structure

A structure runs the call-up whenever another object hits it. The call-up runs before the structure loses any strength, so a hit that does no damage still counts as an attack on the base. This includes a hit a laser fence ignores, a hit on an immune bridge repair hut, and a hit a firestorm wall absorbs by draining the Firestorm Defense charge. The same hit starts the owner’s attacked state.

A structure with an UndeploysInto vehicle counts as a deployed vehicle, not as part of the base, and never runs the call-up. A construction yard is the exception and counts as part of the base.

A protected object

ToProtect=yes makes objects of that type run the call-up when a computer house owns them. A protected structure runs it a second time, on top of the structure call-up above. The second run is refused if the first one started the attacker’s cooldown.

What the house announces

A hit on a structure can also produce a spoken warning and spring the owner’s attacked trigger event. This happens when all of the following hold:

the hit came from another object;
the hit did damage, so a hit that was absorbed entirely does not count;
the structure does not set Insignificant=yes;
the structure is not a deployed vehicle.

The warning depends on the owner:

If the local player controls the owner, the radar marks the structure’s cell and the base-under-attack line plays.
If the owner is allied to the local player, the ally-attacked line plays instead. Outside a campaign, this line also requires that the owner’s country does not set MultiplayPassive=yes.

After either line, the owner plays no further warning and marks no further radar cell for SpeakDelay minutes.

Every such hit also springs the attacked event on each trigger tag attached to the owner, whether a computer or a human controls it. SpeakDelay does not delay the event.

The attacked state

The expert AI is a computer house’s periodic decision pass. It runs every 7 to 7.5 seconds and also fires the computer’s superweapons. A computer house whose country sets MultiplayPassive=yes never runs it.

A computer house is in its attacked state for one minute after the most recent hit on one of its structures. The state starts and ends only when the house’s expert AI runs, so each change can come up to 7.5 seconds late. A house that never runs the expert AI never enters the state.

Every computer house that runs the expert AI is in the attacked state for the first minute of the match, before anything attacks it, because the time of the last hit starts at zero.

Two decisions read the state:

A house in the attacked state never orders a fire sale. A fire sale sells the whole base when the house owns structures but none of them can produce anything. In a Short Game it can keep one structure, as FireSaleKeepThreshold describes.
A computer-owned aircraft on Guard does not look for enemy vehicles caught far from their owner’s base.

Anger and the declared enemy

Each house holds one anger figure for every other house, and none for itself. Its declared enemy is the house it holds the most anger toward, among the houses it is allowed to choose.

What raises it

Every hit from another house’s object raises the anger the damaged object’s owner holds toward that house. This applies to every house, computer or human, allied or not, and to damage to any object, not only to structures.

The increase is the damaged type’s build cost multiplied by the fraction of its Strength the hit removed, with the fraction dropped. For a structure, the build cost is its Cost less the cost of any free unit it comes with, and less the average price of the aircraft it comes with on a helipad. For example, a vehicle costing 1000 with Strength=400 that loses 100 strength raises anger by 250.

The damage counted is the damage applied after armor and distance falloff. On a killing blow it is cut back to the strength that was left. A hit worth less than one whole point adds nothing. Healing counts as negative damage, so being repaired by another house’s object lowers the anger toward that house.

These hits add no anger:

a hit that a laser fence ignores;
a hit on an immune bridge repair hut;
a hit that an active firestorm wall absorbs.

A hit on an Immune=yes object adds anger for its damage without the warhead’s Verses against the object’s Armor or the distance falloff.

A house also gains one point of anger toward a house it turns hostile to, whether or not the two were allied. Breaking an alliance and the Make enemy trigger action both do this. Outside a campaign, neither happens when either country sets MultiplayPassive=yes.

How the enemy is chosen

A house re-runs the choice whenever damage, an alliance change or the first-enemy pick changes its anger. The house with the highest anger figure becomes the declared enemy, skipping defeated houses and current allies. A figure must be above zero to win. A tie goes to the house created first. When no house qualifies, the house has no declared enemy.

Alliances and defeats change the choice directly:

Allying with a house zeroes the anger held toward it and drops it as the declared enemy.
When a computer house’s declared enemy is defeated, the computer house zeroes its anger toward that house. It then has no declared enemy until its anger next changes.

Apart from those two resets, the choice only skips defeated houses and allies. Their figures stay. An ally’s figure, including anger from hits after the alliance formed, counts again once the alliance ends.

Decay

Every 100 frames, each anger figure above 1 drops by 1.

Picking a first enemy

Outside a campaign, a computer house with no declared enemy picks one. On each run of the expert AI, it adds one point of anger toward another house when all of the following hold, tested in this order:

its AIHateDelays countdown has run out; the countdown is set once when a skirmish or multiplayer match starts;
it has no declared enemy;
the game is not a campaign;
its country does not set MultiplayPassive=yes;
it has a base center, which it has while at least one of its structures is on the map.

The point goes to the house whose base center is nearest, counting only houses that are not defeated, that the picking house does not count as allies, and whose country does not set MultiplayPassive=yes.

The point then re-runs the choice, so the eligible house with the most anger becomes the declared enemy, whichever house received the point. After a declared enemy is defeated, other houses often still hold anger, and the first point makes the angriest of them the enemy.

What the declared enemy drives

Whether a non-defensive AI trigger can be considered at all. Every trigger condition except the one about the house’s own holdings measures the declared enemy.
Which house the computer’s ion cannon rates targets from, and which house’s structures its multi-missile and chemical missile choose between.
Whether the computer fires its hunter seeker and drop pods. Outside a campaign, a computer house’s hunter seeker hunts only the declared enemy’s objects.
The preferred house for the two team missions that attack or move to a structure with a named property.
EnemyHouseThreatBonus in target scoring, and the low score a house ordered to hunt everything gives to objects the declared enemy does not own. Both belong to target selection.

The threat map

Each house keeps one threat figure for every region of the map. A region is a block of 4 by 4 cells. Every infantry, vehicle, aircraft and structure adds its type’s ThreatPosed to the maps of the other houses, never to its owner’s.

Allies are handled by who controls the house. A human-controlled house leaves its allies’ objects off its map. A computer house counts its allies’ objects as threats like everyone else’s.

Each contribution is spread over a 3 by 3 block of regions around the object’s region. The center region gets the full figure, the four regions beside it get half, and the four corner regions get a quarter, each with the fraction dropped. Removing a contribution subtracts the same shares.

A region never drops below zero. Any part of a subtraction that would take it below zero is lost, so after such a subtraction the map can end up higher than the objects on it account for.

What adds and removes a contribution

Each event below adds or removes a contribution, spread around the cell in the second column. That cell is not always where the object currently stands. For infantry, vehicles and aircraft, the recorded cell is the last cell the object finished moving into on the ground, or the cell where an aircraft last landed.

Event	Cell the contribution is spread around
An object is placed on the map	The cell it appears in
An object is taken off the map, for example when destroyed or loaded into a transport	For infantry, vehicles and aircraft, the recorded cell; for a structure, the cell it stands in
An infantry or vehicle finishes moving into a cell in a different region	Added around the new cell and removed around the previous one
An object changes owner	The same cell as when it is taken off the map. The previous owner’s map gains the contribution, and the new owner’s map loses it.
A small visceroid merges into a large one	Added around the large visceroid’s recorded cell, with nothing removed

The visceroid merge is the only event that does not balance. The large visceroid’s contribution is added on top of the small visceroid it replaced, and only the large figure is removed later. The small visceroid’s ThreatPosed therefore stays on the map where the merge happened.

Rebuilding the map

A house clears its map and rebuilds it from every object in the match in two situations:

it allies with another house;
an alliance between it and another house is broken, in which case both houses rebuild.

Outside a campaign, every house allies with the neutral Special house when the match starts, after the map’s objects are placed, so every house rebuilds its map then. In a campaign, alliances are set before any object exists, so no rebuild happens at the start. Otherwise the map changes only through the events in the table above.

What reads the map

The computer’s multi-missile and chemical missile strike the declared enemy’s structure that stands in the highest-rated region.
A team that is under way and has fallen under strength regroups at one of its house’s unarmed structures. Each structure is scored by its distance from the team multiplied by one more than its region’s figure, and the score is halved for a structure that repairs vehicles. The lowest score wins.
The least-threat and greatest-threat structure properties a team script can ask for.
The pathfinder, through the moving object’s ThreatAvoidanceCoefficient:
- A diagonal shortcut is refused when the figure at the cell where it starts, multiplied by the coefficient, reaches 1.
- A straight-line shortcut counts each cell whose figure multiplied by the coefficient reaches 0.01 as threatened. Depending on the pass, one threatened cell or more than three abandon the shortcut.
- The coarse corridor search of route search adds the region figure, multiplied by the coefficient, to the price of each step.

Calling defenders back

When the call-up is refused

The call-up does nothing when any of the following holds, tested in this order. Every condition concerns the damaged object and the attacker. None depends on which defenders the house has.

Refused when	Detail
The attacker is an ally of the damaged object’s owner
A human controls the owner	In a campaign, the house under player control; otherwise any house a human plays
The damaged object has a primary weapon	Campaigns only. An armed structure or protected object calls no one back, even when its weapon cannot hit the attacker, such as an anti-aircraft structure hit by infantry.
The attacker is not an infantry or a vehicle	Aircraft and structures never provoke a response
The damaged type sets `Insignificant=yes`
The attacker’s cooldown from an earlier call-up is still running	See the attacker’s cooldown

A call-up that passes these checks empties the house’s low-priority teams before it looks for defenders.

The strength budget

The call-up looks for defenders worth the attacker’s ThreatPosed multiplied by ComputerBaseDefenseResponse in [AI]. That product is the budget. An attacker whose type has ThreatPosed=0 gives a budget of zero, and no one is called back, whatever the multiplier is.

A qualifying object that is already targeting the attacker is not called back again. Its ThreatPosed is subtracted from the budget instead. Once the budget reaches zero or below, the search for defenders stops.

With ComputerBaseDefenseResponse=3, suppose one object is already targeting the attacker, and its ThreatPosed is three times the attacker’s. It brings the budget to exactly zero, so no defender is called back. Whether the budget ends at exactly zero or below it decides whether the cooldown starts.

Teams are emptied first

Before looking for defenders, the call-up empties every team of the house whose TeamType Priority is below SuspendPriority in [General]. Each emptied team is suspended for SuspendDelay minutes and does nothing until that time has passed. Its former members have no team for the rest of the call-up, which lets them qualify as defenders.

Teams are emptied on every call-up that passes the refusal checks, even when the budget is zero or no defender qualifies. A call-up that sets no cooldown runs again on the attacker’s next hit and restarts the suspension. An attack that keeps hitting without starting a cooldown therefore keeps those teams empty and suspended.

What happens when the suspension ends depends on whether the team had started. A team has started once it has reached full strength or been flagged into action, and nothing clears that mark. Full strength here is the member count its TaskForce asks for, not hit points.

A team that had started is deleted, because it has no members.
A team that had not started resumes recruiting. Outside a campaign, the ordinary rule dissolves it if it is still empty DissolveUnfilledTeamDelay frames after it was created.

The call-up reads four settings from rules.ini. These are example values; the linked key pages give the defaults.

[AI]
ComputerBaseDefenseResponse=4 ; budget is the attacker's ThreatPosed times 4

[General]
BaseDefenseDelay=1            ; minutes before any house answers the same attacker again
SuspendPriority=10            ; teams with a Priority below 10 are emptied
SuspendDelay=3                ; minutes an emptied team stays suspended

Which objects qualify

The call-up examines infantry first, then vehicles. Aircraft and structures are never called back. Both passes stop once the budget reaches zero or below. An object is rejected on the first of these that applies:

Rejected when	Detail
It is inactive, or another house owns it
It is on a team whose TeamType does not set `IsBaseDefense=yes`	A member of a base-defense team can be called back; a member of any other team cannot
Its recruitable state or its autocreate-recruitable state is off	Both start set; see recruitment
It has no primary weapon
Its current mission sets `Recruitable=no`	Campaigns only
Its weapon’s warhead has a `Verses` value of exactly `0%` against the attacker’s `Armor`	The primary weapon, or the elite weapon for an elite object
It is not in the same movement zone as the damaged object	Its destination is compared with the damaged object’s, using its `MovementZone`
Its rating is zero	See below

An object that passes these checks and is already targeting the attacker reduces the budget. Otherwise it gets a rating, which measures how much strength it can bring against the attacker. The rating is zero, and the object is dropped, when any of the following holds, tested in this order:

it is targeting something else that has a primary weapon;
its mission is Harvest;
its ThreatPosed is 0.

Otherwise its rating is its ThreatPosed multiplied by 1024 when the attacker is already within its primary weapon’s range. When the attacker is out of range, the rating is divided by the distance beyond that range, measured in multiples of the object’s top speed. The divisor is at least 1, and the rating never drops below 1. A closer or faster object therefore rates higher.

The shortlist and the orders

The call-up keeps a shortlist of up to six candidates, shared between infantry and vehicles. The first six candidates fill it in the order they are examined, without being compared.

After the list is full, a candidate whose rating beats a recorded low replaces the entry whose rating equals the recorded low. The recorded low starts at zero and is updated only by candidates examined after the list filled. No entry holds zero, so the first replacement attempt always fails.

The table follows eight candidates through the list with example ratings.

Candidate	Rating	Shortlist after it	Recorded low after it
1	30	30	0
2	25	30, 25	0
3	40	30, 25, 40	0
4	20	30, 25, 40, 20	0
5	35	30, 25, 40, 20, 35	0
6	45	30, 25, 40, 20, 35, 45 (full)	0
7	50	unchanged: 50 beats the recorded low, but no entry holds `0`, so nothing is replaced	20
8	28	30, 25, 40, 28, 35, 45	25

The rule has three consequences:

The first candidate examined after the list fills is always dropped, whatever its rating. It only sets the recorded low. Because infantry are examined first, when exactly six infantry qualify, the first qualifying vehicle is the one dropped. Later vehicles compete normally and can replace infantry.
While the recorded low is below every entry, every candidate is dropped. This happens when the first candidate after the list fills is rated below all six, because that candidate sets the recorded low to its rating. It ends once a candidate rated at or above the list’s lowest entry is examined. That candidate is dropped too, but it sets the recorded low to the list’s lowest entry, so the next candidate competes normally.
When several entries share the recorded low, a replacing candidate overwrites all of them. The list can then hold one object several times, and each copy counts toward the budget when orders are given.

The shortlist is sorted from highest to lowest rating, and defenders are ordered in that sequence. Each takes the Rescue mission on a 66 percent chance and Area Guard otherwise. A member of an IsBaseDefense=yes team always takes Area Guard. Either way, the attacker becomes the defender’s target, and the damaged object is recorded as what it is protecting.

After each order, the defender’s ThreatPosed is added to a running total. Orders stop once the total exceeds the budget. The first defender is therefore always sent, even when it alone covers the whole budget.

A defender on Rescue first attacks the attacker. Once it has no target, it attacks whatever it finds near the damaged object. When nothing is left, it moves to a point its house chooses and switches to Area Guard on arrival:

An object with no offensive value goes to the core of the base, a random point within one base radius of the base center.
Every other object goes to one of the four edge zones at random. An edge zone is the ground in one compass quadrant of the base, between one and two base radii from the center.

For these points, the base radius counts as at least 3 and at most 8 cells.

The attacker’s cooldown

A call-up starts a cooldown of BaseDefenseDelay minutes, set in [General], when the ThreatPosed of the defenders it ordered exceeds the budget. The cooldown belongs to the attacker, not to the defending house. While it runs, no house calls defenders back against that attacker.

These call-ups set no cooldown and run again on the attacker’s next hit:

one that ran out of candidates before the defenders’ total exceeded the budget;
one whose budget reached exactly zero because of objects already targeting the attacker, as in the strength budget example;
one for an attacker whose ThreatPosed is 0.

A budget pushed below zero by objects already targeting the attacker does start the cooldown.

Campaign and skirmish differences

These rules differ between campaigns and skirmish or multiplayer games:

Behavior	Campaign	Skirmish and multiplayer
Picking a first enemy	Never happens	The nearest undefeated house that is not an ally and whose country is not passive, once the countdown expires
A damaged object with a primary weapon	Calls no one back	Calls for help like any other
A candidate whose mission sets `Recruitable=no`	Rejected	Accepted; the mission’s setting is not read
Which houses count as human	The house under player control	Every house a human plays
Breaking an alliance	Always proceeds	Requires that neither country sets `MultiplayPassive=yes`

Settings and state without effect

Whiner=yes on a TeamType has no effect. A team member that takes damage always reports it to its team, which responds as answering damage describes, so the setting never starts a call-up.

The Autocreate Begins… trigger action has no effect on team creation. The team-creation step it was meant to start is disabled, and the step that replaced it does not read what the action sets. AutocreateTime belonged to the same disabled step.

Filter keysRuntime effect

17 of 17

Key	Description	Value	When omitted
`AIHateDelays`global rules	The frames a computer house waits before picking its first enemy, one entry per difficulty.	list of integers	`(empty)`
`Armor`No effect in some scopes14 applicable types	An object type's armor class, or on a country or difficulty setting the divisor of the damage its objects take.	ArmorType	Varies by type
`AvoidThreats`TeamType	Fixes every member's threat avoidance at `1` while it is on the team.	boolean	`no`
`BaseDefenseDelay`global rules	Minutes during which no house calls up base defenders again against an attacker that a call-up has already covered.	floating point	`.25`
`ComputerBaseDefenseResponse`global rules	Multiplies an attacker's ThreatPosed to size the defenders a computer house calls up.	integer	`3`
`Cost`6 applicable types	The credit price of one object of this type, or the multiplier a country or a difficulty applies to every price it pays.	integer	Varies by type
`IsBaseDefense`BuildingType, TeamType	Gives a BuildingType the computed ratings the computer picks base defenses by, or counts a TeamType against its house's defensive team total.	boolean	`no`
`MovementZone`AircraftType, BuildingType, InfantryType, UnitType	Selects which terrain the type can cross when the game decides whether it can reach a cell.	mzonetype	`Normal`
`Priority`TeamType, Sounds	How firmly a team holds its members against other teams, or how hard a sound competes for a playback channel.	integer	Varies by type
`Recruitable`mission behavior	Whether an object in this mission may be taken onto a team.	boolean	`yes`
`Strength`No effect in some scopes12 applicable types	The maximum strength of most object types; wall overlays use it as a per-hit damage threshold.	integer	Varies by type
`SuspendDelay`global rules	Minutes of game time a team stays suspended after a base attack emptied it.	floating point	`2`
`SuspendPriority`global rules	The TeamType priority a team must reach to survive a base attack.	integer	`20`
`ThreatAvoidanceCoefficient`AircraftType, BuildingType, InfantryType, UnitType	How heavily the type weighs the region threat figures when the pathfinder prices a route.	floating point	`0`
`ThreatPosed`AircraftType, BuildingType, InfantryType, UnitType	How much danger the type represents, used by the region threat map and base-defense call-ups.	integer	`0`
`ToProtect`AircraftType, BuildingType, InfantryType, UnitType	Whether damage to the object makes its computer house call defenders back to it.	boolean	`no`
`Verses`WarheadType	The percentage of a weapon's damage the warhead delivers against each armor class, in armor order.	string	`100%,100%,100%,100%,100%`

History

Changed0.2.0In development
Pick a computer house's first enemy from outside its alliance