TLB - IEDs

An Arma 3 addon that adds TLB-branded copies of the eight vanilla and ACE IED types. Each one leaves a persistent crater where it detonates, without launching or trapping the vehicle that set it off.

Requires CBA_A3 and ACE3 (ace_explosives). Built and tested against ACE 3.21.2, Arma 3 v2.10+.

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What it does

Standard ACE IEDs detonate and leave nothing behind. These behave identically in every other respect. Defusing, pressure plates, cellphone, clacker and dead man switch are all inherited unchanged. What is new is that they scar the ground permanently, so a route that has been hit looks like it has been hit for the rest of the mission.

The hard part isn't spawning the crater. It's spawning a solid 3D object inside the hull of the vehicle that just drove over it, without the physics engine firing that vehicle into the sky. See The anti-stuck problem.

Demo

Screenshots

Lands on the crater, not inside it, and drives out.	The crater is permanent: the route stays scarred.
Each crater is randomly rotated, so repeat hits never look cloned.	Crater size is a per-IED setting. See Crater selection.

Installation

Clients. Load @TLB - IEDs alongside CBA and ACE.

Server. Copy @TLB - IEDs to the server, add it to -mod=, and install keys/TLBIEDs01.bikey into the server's keys/ folder so the signature verifies.

Classes

Display name	Mine class	Zeus module	Default crater
TLB IED (Large, Dug-in)	TLB_IEDLandBig	TLB_ModuleExplosive_IEDLandBig	Large
TLB IED (Large, Dug-in, Pressure Plate)	TLB_IEDLandBig_Range	TLB_ModuleExplosive_IEDLandBig_Range	Large
TLB IED (Large, Urban)	TLB_IEDUrbanBig	TLB_ModuleExplosive_IEDUrbanBig	Large
TLB IED (Large, Urban, Pressure Plate)	TLB_IEDUrbanBig_Range	TLB_ModuleExplosive_IEDUrbanBig_Range	Large
TLB IED (Small, Dug-in)	TLB_IEDLandSmall	TLB_ModuleExplosive_IEDLandSmall	Medium
TLB IED (Small, Dug-in, Pressure Plate)	TLB_IEDLandSmall_Range	TLB_ModuleExplosive_IEDLandSmall_Range	Medium
TLB IED (Small, Urban)	TLB_IEDUrbanSmall	TLB_ModuleExplosive_IEDUrbanSmall	Medium
TLB IED (Small, Urban, Pressure Plate)	TLB_IEDUrbanSmall_Range	TLB_ModuleExplosive_IEDUrbanSmall_Range	Medium

Those are only the defaults. Every IED type has its own CBA setting, so you can give each one any crater size, turn its crater off, or set it to Random. See Crater selection.

In Eden they sit under Empty → Explosives → TLB IEDs. In Zeus, place them through the modules in the right-hand column.

Only the display name, the ammo class and the crater differ from the originals. Craters are not added to the stock vanilla/ACE IEDs, so existing missions behave exactly as they always have. Mission makers opt in by placing the TLB versions.

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How it works

1. Catching the detonation

The hook lives on the ammo, not on the mine object:

class TLB_IEDLandBig_Remote_Ammo: IEDLandBig_Remote_Ammo {
    TLB_craterSetting = "TLB_IEDs_craterLandBig";   // which CBA setting decides
    TLB_craterDefault = 3;                          // what it defaults to
    class EventHandlers {
        init = "call TLB_IEDs_fnc_initMine";
    };
};

Note that the crater itself is not named here. Each ammo class only points at the setting that decides it, so crater choice stays configurable at runtime rather than baked into the PBO.

That init handler fires wherever the mine is local. It is the same mechanism ACE uses for its trip flares, and putting it on the ammo means it works however the IED reached the world, whether Eden, a Zeus module, createMine, or an ACE player placement.

fnc_initMine.sqf then attaches an Explode handler to the mine:

_mine addEventHandler ["Explode", {
    params ["_projectile", "_posASL"];
    ...
}];

Explode fires only on a genuine detonation. Defusing deletes the mine without firing it, so EOD work never leaves a phantom crater. No extra bookkeeping is needed to tell the two apart.

2. Building the crater

The Explode handler asks the server to create the crater, so it exists once and globally. fnc_spawnCrater.sqf snaps it flush to the terrain, gives it a random rotation (so repeat hits along one route don't look cloned) and disables damage on it. It appears instantly.

3. The anti-stuck problem

Land_ShellCrater_02_* are 3D bowls with real collision geometry. A crater appearing inside a vehicle's hull is deep mesh penetration, and the physics engine resolves that the only way it knows how: by firing the vehicle into the air.

The fix is to make sure nothing is standing there when the crater appears. Anything inside the crater's footprint is raised one metre first, and the crater forms underneath it. No penetration, so nothing to resolve. The vehicle then drops onto the finished crater and drives out normally.

Ordering is the whole trick. The lift is fired from the Explode handler as a global event, straight to every machine, before the server is even asked to build the crater:

["TLB_IEDs_blastLift",   [_craterType, _posASL]]          call CBA_fnc_globalEvent;
["TLB_IEDs_spawnCrater", [_craterType, _posASL, _radius]] call CBA_fnc_serverEvent;

The crater has to round-trip through the server before it can exist anywhere, so the lift is always ahead of the thing it protects against, however slow the link is. A one-second hold then stops the vehicle falling back down in that gap. It holds height above ground, so it keeps working while the vehicle is still moving.

Two deliberate non-behaviours, both learned the hard way:

• Crew are never lifted. Only troops on foot are candidates (isNull objectParent). Lifting a unit that is sitting in a vehicle rips it out of its seat, and the vehicle lift already carries its crew along with it.
• disableCollisionWith is not used. That was the original design, and it was tested: the pairwise suppression was verifiably applied to the vehicle and the vehicle was still launched. It does not work against a static crater object, so it was removed rather than left in looking like a safety net.

The lift radius is read from the crater model itself via sizeOf rather than hardcoded, so only things genuinely in the hole get moved, and it stays correct if the crater types are ever changed.

Each machine only moves what is local to it, because setPos on a remote object desyncs.

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Settings

Under TLB - IEDs in the CBA settings menu. All server-forced.

Setting	Default	Notes
Spawn craters	on	Master switch.
Lift infantry too	on	Also lift troops on foot. Never affects vehicle crew.
Lift height	1.0 m	Raise this if a vehicle still catches the crater's lip.
Lift hold	1.0 s	Stops a lifted vehicle dropping back before the crater exists. 0 for a single instant lift.
Max craters	0	0 = unlimited; craters are permanent. Raise above 0 only as a safety valve on very long operations, where it removes the oldest first.

Crater selection

Each of the eight IED types has its own Crater: ... setting, so a dug-in large IED and an urban one can leave completely different holes, and the pressure-plate variants can differ from the command-detonated ones. Options:

Option	Object
None	no crater for this IED type
Small	Land_ShellCrater_01_F
Medium	Land_ShellCrater_02_small_F
Large	Land_ShellCrater_02_large_F
Extra Large	Land_ShellCrater_02_extralarge_F
Random	a different one of the four sizes on every detonation

Random is resolved once, on the machine the IED detonated on, and the chosen classname is then sent to everyone. If each machine rolled its own, the lift would size itself against a different crater than the one that actually appears.

Adding another size is a one-line change to TLB_IEDs_craterTypes in XEH_preInit.sqf, and it offers itself in all eight settings automatically.

Diagnostics

The addon logs to the .rpt. A healthy detonation looks like this:

[TLB_IEDs] preInit complete
[TLB_IEDs] armed TLB_IEDLandBig_Range
[TLB_IEDs] lifted 1 entities by 1m (r5.5)
[TLB_IEDs] crater Land_ShellCrater_02_large_F at [...]

Those map to the four stages, which makes a failure easy to localise:

Last line seen	Meaning
nothing	The PBO prefix is wrong. Look for Script \tlb\ieds\XEH_preInit.sqf not found.
preInit complete	Functions loaded, but the ammo init handler never fired.
armed	The mine was hooked, but Explode never fired, so it was defused rather than detonated. Or this IED type's crater setting is None.
lifted	Crater creation failed; check the classname in TLB_IEDs_craterTypes (XEH_preInit.sqf).

Building from source

Requires Arma 3 Tools (AddonBuilder, DSSignFile).

.\build.ps1                     # build + sign into dist\
.\build.ps1 -Deploy             # also copy into the Arma !Workshop folder
.\build.ps1 -KeyName TLBMisc3   # sign with an existing key instead

The default key TLBIEDs01 is generated into private\ on first build. private\ is gitignored: a .biprivatekey must never be published, since anyone holding it can sign a PBO that your server will accept as genuine TLB content. Distribute only the .bikey.

Two things the build script does that are worth keeping:

• It passes -prefix=tlb\ieds explicitly. AddonBuilder ignores $PBOPREFIX$ and silently names the prefix after the source folder instead.
• It reads the prefix back out of the finished PBO and fails the build if it is wrong. A bad prefix produces no build error at all. It surfaces only in game as a missing script, which is a miserable way to find out.

Packing uses -packonly. There are no models or textures here, only config and SQF, so binarising would buy nothing and add a failure mode.

Repository layout

addons/tlb_ieds/
  config.cpp              CfgPatches, XEH registration, editor subcategory
  CfgAmmo.hpp             8 ammo classes, crater assignment, detonation hook
  CfgVehicles.hpp         8 mines + 8 Zeus modules
  XEH_preInit.sqf         function compilation, CBA settings, event registration
  functions/
    fnc_initMine.sqf      attaches the Explode handler
    fnc_liftEntities.sqf  the anti-stuck lift (runs on every machine)
    fnc_spawnCrater.sqf   creates the crater (server only)
build.ps1                 pack, verify prefix, sign, optionally deploy
mod.cpp                   launcher metadata

Testing

1. Load alongside CBA and ACE.
2. In Eden, place a player in a vehicle and a TLB IED (Large, Dug-in, Pressure Plate) on a road.
3. Drive over it. The IED detonates, a large crater appears at the exact spot, and the vehicle is not launched. It lands on the crater and, if still driveable, pulls out normally.
4. Confirm the crew are still in the vehicle.
5. Defuse a second IED instead of triggering it, and no crater should appear.
6. Repeat on a dedicated server with two clients, to confirm the crater appears for both and that the lift applies on whichever machine owns the vehicle.

About TLB MilSim

We are a MilSim unit, and this mod was built mainly for our own operations. We are sharing it with the rest of the community in case it is useful to anyone else, and because we would like to hear suggestions and ideas for improvements.

If you have one, or you hit a problem, come and tell us:

discord.gg/TLBMilSim

Bug reports and feature requests are equally welcome on the issue tracker.

Contributing

Pull requests are welcome, and so are bug reports and ideas on the issue tracker or in Discord.

By opening a pull request you agree that your contribution is licensed to TLB MilSim under the same terms as the rest of the project.

License

Arma Public Licence No Derivatives (APL-ND).

In plain terms, and the LICENSE file is what actually governs:

• Use it freely. Put it on your server, use it in your missions.
• Share it unmodified. Passing the mod along as-is is fine.
• Do not sell it, and do not use it outside Arma.
• Do not distribute a modified or repackaged version. That includes bundling it inside another mod, or reskinning it under different branding.

The TLB and TLB MilSim names and the logo are not covered by the licence and remain ours.

If you want to do something the licence does not allow, ask us in Discord. We are much more likely to say yes than you might expect.

Credits

Built for TLB MilSim.

Thanks to ACE3, whose ace_explosives source is where we learned that a mine's ammo class can carry an init handler and that mines respond to the Explode event. No ACE code is used or included here.