IRS IR Smoke Missile Countermeasure

IRS — IR-Smoke Missile Countermeasure System (per-vehicle table, upgrade-level behavior)

Source-verified 2026-06-21 against then-current master cf2a6d6a4; current origin/master is 0139a346, so recheck cited paths before current-head claims. Paths relative to Missions/[55-2hc]warfarev2_073v48co.chernarus/ unless noted. Arma 2 OA 1.64.

The IRS (IR Smoke) module is WASP's ground-vehicle missile countermeasure system. When an IR-guided missile is fired at a qualifying vehicle, the system deploys smoke grenades and attempts to deflect the missile's trajectory. It is entirely distinct from the vanilla CM (WFBE_C_MODULE_WFBE_FLARES) flare path used by air vehicles.

---

Module Gate

IRS is guarded by a single flag:

Constant	Default	Where set
WFBE_C_MODULE_WFBE_IRSMOKE	1 (enabled)	Common/Init/Init_CommonConstants.sqf:814

IRS_Init.sqf is compiled only when this flag is > 0:

if ((missionNamespace getVariable "WFBE_C_MODULE_WFBE_IRSMOKE") > 0) then {
    Call Compile preprocessFileLineNumbers "Common\Module\IRS\IRS_Init.sqf"
};

Common/Init/Init_Common.sqf:339

Both Client_BuildUnit.sqf and Server_BuyUnit.sqf check this same constant before attaching the incomingMissile event handler or setting wfbe_irs_flares on a vehicle. Client_BuildUnit.sqf:545, Server_BuyUnit.sqf:155.

---

Global Constants (IRS_Init.sqf)

Constant	Value	Meaning
WFBE_IRS_AREA_OPERATING	35 m	Smoke grenade must land within this radius of the vehicle for the deflection attempt to trigger
WFBE_IRS_AUTO_DETECT_RANGE	200 m	Missile is tracked once it enters this range of the vehicle
WFBE_IRS_FLARE_DELAY	60 s	Cooldown between consecutive IRS deployments on a single vehicle
WFBE_IRS_MISSILE_CHECK_RANGE	200 m	IRS actions are checked when the missile enters this range

All four defined at Common/Module/IRS/IRS_Init.sqf:11-14.

---

Per-Vehicle Table

Each entry registers a vehicle type as <type>_IRS = [dodgeChance%, smokeCount] in missionNamespace. An entry is only registered if (a) the vehicle type is already defined in the mission's core variable space, and (b) configFile >> "CfgVehicles" >> type >> "smokeLauncherGrenadeCount" resolves to a number — i.e., the vehicle has smoke launchers in its A2 config. Common/Module/IRS/IRS_Init.sqf:49-56.

Class name	Dodge chance (%)	Base smoke count	Notes
AAV	50	2	IRS_Init.sqf:18
BAF_FV510_W	70	3	IRS_Init.sqf:19
BAF_FV510_D	70	3	IRS_Init.sqf:20
BMP2_CDF	50	2	IRS_Init.sqf:21
BMP2_Gue	50	2	IRS_Init.sqf:22
BMP2_INS	50	2	IRS_Init.sqf:23
BMP2_TK_EP1	50	2	IRS_Init.sqf:24
BMP3	65	3	IRS_Init.sqf:25
BTR90	65	2	IRS_Init.sqf:26
LAV25	65	2	IRS_Init.sqf:27
M1126_ICV_M2_EP1	60	1	Stryker ICV; IRS_Init.sqf:28
M1126_ICV_mk19_EP1	55	1	Stryker ICV MK19; IRS_Init.sqf:29
M1129_MC_EP1	60	1	Stryker MC; IRS_Init.sqf:30
M1135_ATGMV_EP1	60	1	Stryker ATGM; IRS_Init.sqf:31
M1128_MGS_EP1	60	1	Stryker MGS; IRS_Init.sqf:32
M1133_MEV_EP1	60	1	Stryker MEV; IRS_Init.sqf:33
M1A1	70	4	IRS_Init.sqf:34
M1A1_US_DES_EP1	70	4	Desert M1A1; IRS_Init.sqf:35
M1A2_TUSK_MG	75	4	IRS_Init.sqf:36
M1A2_US_TUSK_MG_EP1	75	4	IRS_Init.sqf:37
M2A2_EP1	65	3	Bradley A2; IRS_Init.sqf:38
M2A3_EP1	65	3	Bradley A3; IRS_Init.sqf:39
M6_EP1	60	3	Linebacker; IRS_Init.sqf:40
T72_CDF	65	4	IRS_Init.sqf:41
T72_INS	65	4	IRS_Init.sqf:42
T72_Gue	65	4	IRS_Init.sqf:43
T72_RU	65	4	IRS_Init.sqf:44
T72_TK_EP1	65	4	IRS_Init.sqf:45
T90	80	4	Highest dodge chance in the table; IRS_Init.sqf:46

Total: 29 entries.

The "Base smoke count" column is the value stored at index 1 of the <type>_IRS array. This is the count assigned to wfbe_irs_flares at spawn for a side with upgrade level 1. At upgrade level 2 it is doubled (see Upgrade Levels below).

Silent exclusion rule: A vehicle type not present in this table — or whose class is undefined in the mission's variable namespace, or which lacks smokeLauncherGrenadeCount in CfgVehicles — receives no IRS registration and no wfbe_irs_flares variable. A vehicle type not in this table receives no wfbe_irs_flares variable and no incomingMissile IRS event handler — the exclusion happens at spawn/build time in Client_BuildUnit/Server_BuyUnit, not at event-fire time. IRS_Init.sqf:49-56.

---

WFBE_UP_IRSMOKE Upgrade

Constant	Index	File
WFBE_UP_IRSMOKE	18	Common/Init/Init_CommonConstants.sqf:55

The upgrade has 2 levels across all factions. Upgrades_USMC.sqf:78 (line 78: 2, //--- IR Smoke; all other faction upgrade files confirm the same max-level value).

Costs and research times (all factions, identical)

Level	Cost (money, supply)	Research time (s)	Prerequisite
1	[3000, 0]	120	WFBE_UP_HEAVY level 3
2	[9000, 0]	180	None (no link)

Sources: Common/Config/Core_Upgrades/Upgrades_USMC.sqf:51,78,113,140 (costs, levels, links, times). The RU faction upgrade file confirms identical values at the same line offsets: Common/Config/Core_Upgrades/Upgrades_RU.sqf:51.

The WFBE_C_UPGRADES_<side>_ENABLED flag for IR Smoke at index 18 is gated on WFBE_C_MODULE_WFBE_IRSMOKE > 0 — if the module is disabled the upgrade entry is false and the research node does not appear in the buy menu. Upgrades_USMC.sqf:24.

---

Upgrade-Level Behavior

Level 1 — basic IRS

When a player-purchased or player-built vehicle is built (Client_BuildUnit.sqf:354-367 or Server_BuyUnit.sqf:118-124):

1. The side upgrade level is checked: ((sideJoined) Call WFBE_CO_FNC_GetSideUpgrades) select WFBE_UP_IRSMOKE > 0.
2. The vehicle's <type>_IRS entry is retrieved from missionNamespace.
3. wfbe_irs_flares is set to _get select 1 (the base smoke count from the table above). Client_BuildUnit.sqf:363.
4. An incomingMissile EH for WFBE_CO_MOD_IRS_OnIncomingMissile is attached. Client_BuildUnit.sqf:364.

On each trigger the vehicle announces via vehicleChat (localized string STR_WF_CHAT_IRS_Deployed): "Deploying IR Smoke! %1 ammunitions remaining." IRS_OnIncomingMissile.sqf:33, stringtable.xml:317.

At upgrade level < 2, the player crew hears a single one-shot sound: playSound ["inboundMissileGround", true]. IRS_OnIncomingMissile.sqf:37.

Level 2 — doubled smoke + continuous warning

At upgrade level 2, the base smoke count from the table is doubled before being stored in wfbe_irs_flares:

if (((sideJoined) Call WFBE_CO_FNC_GetSideUpgrades) select WFBE_UP_IRSMOKE > 1) then {
    _getSelectOne = _getSelectOne * 2;
};
_vehicle setVariable ["wfbe_irs_flares", _getSelectOne, true];

Client_BuildUnit.sqf:361-363

Note: the doubling is applied only in Client_BuildUnit (player-spawned vehicles). Server_BuyUnit (AI-purchased vehicles) does not apply the level-2 doubling; it always uses _get select 1 unmodified. Server_BuyUnit.sqf:121.

The warning sound at upgrade level 2 changes from a single shot to a looping tone that plays for as long as the inbound missile is alive:

[_projectile] spawn {
    _projectile = _this select 0;
    while {!(isNull _projectile)} do {
        playSound["inboundMissileGround_cont",true];
        sleep 0.2;
    };
};

IRS_OnIncomingMissile.sqf:41-48

This continuous loop runs on the local player's machine only (the outer if ((local player) && (player in crew _vehicle)) guard applies to both branches). IRS_OnIncomingMissile.sqf:28.

---

incomingMissile Event Flow

Both Client_BuildUnit and Server_BuyUnit attach a second incomingMissile handler — the vanilla-tracking HandleATMissiles function — unconditionally for all Tank or Car class vehicles, regardless of IRS module state. HandleATMissiles is compiled at Common/Init/Init_Common.sqf:11; the EH attachment is at Client_BuildUnit.sqf:350. The IRS-specific handler (WFBE_CO_MOD_IRS_OnIncomingMissile) is then added on top if IRS conditions are met.

When an incoming missile fires, IRS_OnIncomingMissile executes this sequence:

Step	Code path	Gate condition
1. Ammo gate	IRS_OnIncomingMissile.sqf:18	Only IR-lock ammo (CfgAmmo >> irLock == 1) triggers IRS
2. Locality gate	IRS_OnIncomingMissile.sqf:20	Vehicle must be local to this machine
3. Crew alive check	IRS_OnIncomingMissile.sqf:21	At least one of driver / gunner / commander must be alive
4. Flare counter check	IRS_OnIncomingMissile.sqf:24	wfbe_irs_flares > 0
5. Cooldown check	IRS_OnIncomingMissile.sqf:24	time - wfbe_irs_lastfired > WFBE_IRS_FLARE_DELAY (60 s)
6. Deploy smoke	IRS_OnIncomingMissile.sqf:25	Spawns IRS_DeploySmoke on the vehicle
7. Update lastfired	IRS_OnIncomingMissile.sqf:26	Sets wfbe_irs_lastfired = time
8. Decrement counter	IRS_OnIncomingMissile.sqf:27	Sets wfbe_irs_flares -= 1, broadcast global (true)
9. Player HUD	IRS_OnIncomingMissile.sqf:28-50	Chat + sound, only if local player is in the vehicle
10. Missile handler	IRS_OnIncomingMissile.sqf:56	If missile is local: spawns IRS_HandleMissile

---

Smoke Deployment (IRS_DeploySmoke.sqf)

IRS_DeploySmoke reads smokeLauncherGrenadeCount, smokeLauncherVelocity, smokeLauncherOnTurret, and smokeLauncherAngle directly from CfgVehicles for the vehicle type to calculate launch arcs. It creates SmokeShellVehicle objects and broadcasts them to clients via WFBE_CO_FNC_SendToClients for particle FX. The shells persist for 55 seconds before deletion. Common/Module/IRS/IRS_DeploySmoke.sqf:11-54.

IRS_CreateSmoke attaches custom particle emitters to each shell for the local visual effect (trail + white phosphorus cloud). Common/Module/IRS/IRS_CreateSmoke.sqf:1-30.

---

Missile Deflection (IRS_HandleMissile.sqf)

The deflection handler runs on the machine that is local to the missile (not the vehicle). It:

1. Waits until the missile enters WFBE_IRS_AUTO_DETECT_RANGE (200 m) of the vehicle. IRS_HandleMissile.sqf:21.
2. Checks that at least one SmokeShellVehicle exists within WFBE_IRS_AREA_OPERATING (35 m) of the vehicle. If none, exits without deflection. IRS_HandleMissile.sqf:26-27.
3. Rolls random 100 against the vehicle's dodge chance (_get select 0). IRS_HandleMissile.sqf:29.
4. On a successful roll, applies iterative deflection via setVectorDirAndUp on the missile over 10 ticks (0.01 s each), scaled by the ammo's maneuvrability config value (defaults to 20 if not set). IRS_HandleMissile.sqf:31-67.

The dodge check is probabilistic — the table value is a percentage chance per missile event, not a guarantee.

---

Rearming Resets Flare Count

Common_RearmVehicle.sqf and Common_RearmVehicleOA.sqf both reset wfbe_irs_flares to the base table value (_get select 1) whenever the vehicle rearmed — provided the current count differs from the table default. This means rearming at a supply truck always restores base flares; it does not re-apply the level-2 doubling. Common/Functions/Common_RearmVehicle.sqf:33-39, Common/Functions/Common_RearmVehicleOA.sqf:23-30.

---

Distinction from the Vanilla CM Module

Feature	IRS (WFBE_C_MODULE_WFBE_IRSMOKE)	Vanilla CM (WFBE_C_MODULE_WFBE_FLARES)
Applies to	Ground vehicles: Tank, Car class	Air vehicles
Trigger	irLock == 1 ammo, incomingMissile EH	incomingMissile EH (CM countermeasures)
Mechanic	Smoke + probabilistic trajectory deflect	Flare countermeasures (vanilla A2 CM)
Upgrade index	WFBE_UP_IRSMOKE = 18	WFBE_UP_FLARESCM = 9
Max levels	2	1

---

Continue Reading

• Upgrades-And-Research-Atlas — full upgrade index, cost tables, and research prerequisite chains for all factions
• Modules-Atlas — master list of all WFBE_C_MODULE_* flags, their defaults, and what they gate
• Factory-And-Purchase-Systems-Atlas — how Server_BuyUnit and Client_BuildUnit spawn vehicles and attach module event handlers
• Gear-Loadout-And-EASA-Atlas — the parallel EASA module for aircraft weapon customization (analogous optional-module pattern)
• Variable-And-Naming-Conventions — WFBE_C_*, WFBE_UP_*, and per-vehicle dynamic variable naming conventions