The Prerequisite System: Difference between revisions

Latest revision as of 17:57, 2 July 2025

The Prerequisite System controls the conditions required to build a certain object. Those conditions are:

Is this object's TechLevel valid?: Checks if the TechLevel of the object is above -1 and below [MultiplayerDialogSettings]→TechLevel.
Is this house not forbidden from owning this object?: Checks if the house is not listed in ForbiddenHouses.
Is this house allowed to own this object?: Checks if the house is listed in RequiredHouses.
Does this house own all the prerequisite structures?: Checks if the house owns the prerequisite structures listed in Prerequisite
Is this object stolen technology?: If the unit contains RequiresStolenAlliedTech=yes, RequiresStolenSovietTech=yes, or RequiresStolenThirdTech=yes, has the apropriate lab get spied upon?

If all conditions are met, the house is theoretically allowed to build that object, signaled by a "New Construction Options" announcement.
Next, the game determines whether the house actually can build the object:

Does the house own a Factory of the appropriate type?: Checks whether the house has at least one structure with Factory matching the object's type.
Can this house own this object?: Checks if your Factory contains atleast 1 Owner listed as this units Owner.
If the object in question is a VehicleType, does the house have a Factory=VehicleType with the same Naval setting as the object?: Checks whether the house has a War Factory if it's trying to build land-based (Naval=no) vehicles, and whether it has a Shipyard if it's trying to build water-based (Naval=yes) vehicles.

Overrides

If an object has a PrerequisiteOverride BuildingType (or multiple BuildingTypes) set, a house will be allowed to build the object as soon as it possesses any single one of those listed BuildingTypes, no matter what prerequisites the object usually requires. (Hence the name.)
The same applies to objects from SecretLab=yes buildings: If a house gains an object through a Secret Lab, it will be allowed to build that object immediately, no matter what prerequisites the object usually requires. Such an object will be buildable even if it has TechLevel=11 set.
In addition, AI players do not check Prerequisite and TechLevel tags when they're trying to build the Power Plants listed under GDIPowerPlant, NodRegularPower, ThirdPowerPlant.
AI players also ignore all Prerequisite settings except TechLevel on all other objects, they build objects in the order dictated by the ai(md).ini file (the order of BuildingTypes is controlled by different methods covered here).

All cases under the presumption that the house owns a factory of the appropriate type.

Prerequisite Groups

A "prerequisite group" refers to a list of structures, and any single one of them is sufficient to fulfill the type. See: Generic Prerequisites.

Bugs/Side-Effects/Unexpected Limitations

Only one building specified by PrerequisiteOverride= activates production, meaning that it's not a cumulative list like Prerequisites=.

Ares can allow more types of prerequisite alternatives, see: https://ares-developers.github.io/Ares-docs/new/prerequisites.html

At least in Red Alert 2 and Yuri's Revenge, the AI players ignore Prerequisites= for building queues, limited instead by AIBuildThis, Owner, RequiredHouses, ForbiddenHouses, and stolen tech requirements.

Also in Red Alert 2, the AITriggerTypes in ai(md).ini instruct the AI player to produce TaskForces disregarding Prerequisites altogether, as well as TechLevel, limited by other factors as above.

@@ Line 24: / Line 24: @@
 : Checks whether the house has a War Factory if it's trying to build land-based ({{f|Naval|no|link}}) vehicles, and whether it has a Shipyard if it's trying to build water-based ({{f|Naval|yes|link}}) vehicles.
 |}
-'''Note:''' If you do not have the appropriate type of {{f|Factory|VehicleType|link}}, but all other prerequisites are fulfilled, you will probably experience the [[EVA_NewContructionOptions#NCO_Bug|NCO bug]].
 ==Overrides==
@@ Line 34: / Line 33: @@
 ==Prerequisite Groups==
-A "prerequisite group" refers to a list of structures, and any single one of them is sufficient to fulfill the "prerequisite group". The following "prerequisite groups" are valid:
+A "prerequisite group" refers to a list of structures, and any single one of them is sufficient to fulfill the type. See: [[Generic Prerequisites]].
-* POWER (corresponds to {{f|PrerequisitePower|link}})
-* PROC (corresponds to {{f|PrerequisiteProc|link}} and {{f|PrerequisiteProcAlternate|link}}{{yro}})
-* BARRACKS (corresponds to {{f|PrerequisiteBarracks|link}} for human players, {{f|BuildBarracks|link}} for AI)
-* FACTORY (corresponds to {{f|PrerequisiteFactory|link}})
-* RADAR (corresponds to {{f|PrerequisiteRadar|link}})
-* TECH (corresponds to {{f|PrerequisiteTech|link}})
-In Firestorm, two additional groups are available:
+=={{bugs}}==
+Only one building specified by <tt>PrerequisiteOverride=</tt> activates production, meaning that it's not a cumulative list like <tt>Prerequisites=</tt>.
+* Ares can allow more types of prerequisite alternatives, see: https://ares-developers.github.io/Ares-docs/new/prerequisites.html
-* GDIFACTORY (corresponds to {{f|PrerequisiteGDIFactory|link}})
+At least in {{ra2}} and {{yr}}, the AI players ignore <tt>Prerequisites=</tt> for building queues, limited instead by [[AIBuildThis]], [[Owner]], [[RequiredHouses]], [[ForbiddenHouses]], and stolen tech requirements.
-* NODFACTORY (corresponds to {{f|PrerequisiteNodFactory|link}})
+Also in {{ra2}}, the [[AITriggerTypes]] in {{ini|ai}} instruct the AI player to produce [[TaskForces]] disregarding <tt>Prerequisites</tt> altogether, as well as [[TechLevel]], limited by other factors as above.
 [[Category: Systems]]
-==RP's 'NEW' Prerequisite System stuff{{rpo}}==
-* <tt>NegativePrerequisite=</tt>
-:If anything on this list is owned by the player, then the object <b>can't</b> be built.
-* <tt>AlternatePrerequisite=</tt>
-:A Clone of {{f|Prerequisite|link}}<tt>=</tt>, if all items on either {{f|Prerequisite|link}}<tt>=</tt>, or <tt>AlternatePrerequisite=</tt> are owned by the player, then the {{f|Prerequisite|link}}<tt>=</tt> condition is considered to be met. (on a side note, more of these clones are wanted)
-* <tt>SovietAdvancedPower=</tt> RPCE only.
-:Revival of {{f|NodAdvancedPower|link}}<tt>=</tt>, but with a new name so as to not conflict with the un-modded game, thereby not allowing the Soviets to build the Nuclear Reactor, which by default is not on that tag, instead the tag is set to NAAPWR, the TS Nod Advanced Power Plant. Basically this tag allows the Soviets to build their 'Advanced Power Plant' when they are low on power, instead of lots of regular Power Plants, as long as they meet the prerequisites for that Advanced Power Plant. in RP v1.10 this was replaced with the new PowerPlants= tag.
-* <tt>PowerPlant=</tt>
-:This is the new version of GDIPowerPlant=, NodRegularPower= and ThirdPowerPlant= listed under the sides header ([GDI], [Nod] and [ThirdSide] are the default 3). Although this is automaticly mapped to the original 3 tags for the original 3 sides, FourthPowerPlant is Obsolete.
-* <tt>PowerPlants=</tt>
-:This is a list of power plants per side under the sides header , which lists BuildingType that are randomly selected when that side requires extra power.
-* <tt>RequiresStolenTech=</tt>
-:New stolen tech logic based on {{f|RequiresStolenAlliedTech|link}}<tt>=yes</tt>, {{f|RequiresStolenSovietTech|link}}<tt>=yes</tt>, and {{f|RequiresStolenThirdTech|link}}<tt>=yes</tt>, which allows the modder to specify a new structure that needs to be spied upon to obtain this unit. the building you need to spy on also requires the tags <tt>IsStolenTech=yes</tt> and <tt>Spyable=yes</tt>
-* <tt>RequiresTheater=</tt>
-:A new prerequisite logic based on the theater of the map you are currently playing. This enables modders to make certain structures or units available in, for example, arctic maps only. This, however, does not work correctly with the AI. The available options for this tag are:
-:* TEMPERATE - the Temperate theater (most maps).
-:* SNOW - the Arctic theater (snowy maps).
-:* URBAN - the Urban theater (some city maps).
-:* DESERT - the Desert theater ([[Image:Yro.png]], some desert maps, older ones use Temperate).
-:* LUNAR - the Lunar theater ([[Image:Yro.png]], Soviet Mission 5).
-:* NEWURBAN - the New Urban theater ([[Image:Yro.png]], most YR Urban maps).
-Note: Other items may have been planned, or wished for future RP versions, but only completed items are on this list.