Give an AI a gun and upgrades¶

At the end of this page you will have an NPC that spawns with a gun in its hand, opens fire at the distance that gun is meant for, and wears a silencer on the barrel. No HUD, no inventory, no workbench and no parts are involved.

An AI fires the exact same weapon assets as the player. Both BP_PlayerCharacter and BP_NPCCharacter implement BPI_WeaponOwner, so a gun you build for the player already works on an AI. See How guns work in this template if that split is new to you.

The two places you will work:

The AI presets: Content/TheLastTemplate/Blueprints/DataAssets/AI/Childs/
The NPC: Content/TheLastTemplate/Blueprints/AI/NPC/BP_NPCCharacter

The gun is on the preset, not on the pawn¶

BP_NPCCharacter has no weapon field. It has one field that decides everything about this NPC, Data NPC, and it ships pointing at DA_NPC_Stand. The gun, the reserve and the way the NPC moves in a firefight are all inside that Data Asset.

Four presets ship, and they are the same preset with a few fields moved:

Preset	`Default Weapon Class`	What it is the example of
`DA_NPC_Roaming`	`BP_Weapon_Pistol_01`	The baseline, wanders and shoots
`DA_NPC_Path`	`BP_Weapon_Pistol_01`	Walks a patrol path
`DA_NPC_Stand`	`BP_Weapon_Pistol_01`	Holds a stand point
`DA_NPC_Melee_Roaming`	`None`	Unarmed, melee only

Unarmed is not a mode flag. It is an empty Default Weapon Class. That single field is the whole difference between DA_NPC_Roaming and DA_NPC_Melee_Roaming.

Warning

Data NPC accepts any child of BP_AIDataAsset, but the firearm fields only exist on BP_NPCDataAsset. Point it at a plain BP_AIDataAsset child and the NPC spawns unarmed with no warning and no error in the log. Duplicate one of the four DA_NPC_* presets and you cannot get this wrong.

Arm an NPC¶

In Content/TheLastTemplate/Blueprints/DataAssets/AI/Childs/, duplicate the preset whose idle behaviour you want. Name it after the role, for example DA_NPC_Shotgun_Stand.
Open it and set Default Weapon Class to a child of BP_WeaponBase, for example BP_Weapon_Shotgun_01.
Set Starting Reserve Ammo to the number of spare rounds this NPC gets.
Save.
Drag BP_NPCCharacter into your level and set Data NPC to your new preset.
Play.

That is the whole job. At spawn, BP_NPCWeaponManager creates the weapon actor, attaches it to the socket named in Weapon Grip Socket_R on the weapon's Data Asset, fills the magazine to Clip Size, and switches the character to the gun's Weapon Overlay. You do not add a mesh to the character, you do not pick an animation set, and you do not touch a graph.

The two firearm fields on the NPC Data Asset:

Field	What it does	Shipped
`Default Weapon Class`	The weapon actor the NPC spawns holding. Empty means melee only	`BP_Weapon_Pistol_01` on three presets, `None` on the melee one
`Starting Reserve Ammo`	Rounds carried outside the magazine	`12` on all four

Ammo, and what it does not have¶

The magazine an NPC starts with is Clip Size on the gun's Data Asset. The reserve is Starting Reserve Ammo on the NPC Data Asset. Those two numbers are the whole fight.

An NPC has no inventory. Ammo boxes are interactables, and only the player interacts, so Munition Class on the weapon and the BP_Interactable_Pickup_Ammo_* actors never come into it. Nothing refills an NPC reserve during play. If you want an NPC that keeps shooting, give it a large Starting Reserve Ammo.

Nothing in BP_NPCCharacter drops the gun when the NPC dies, so the player cannot loot it. If you want that, spawn one of the pickup children in Content/TheLastTemplate/Blueprints/Environments/Interactable/Pickup/Weapons/Childs/ where the body falls.

Drawn or put away¶

There is no "start holstered" field. The gun goes into the hand at spawn. After that, BP_AIBrain decides when the weapon comes out and when it goes away, and moves it between Weapon Grip Socket_R and Unholster Humanoid Socket, both read from the weapon's Data Asset.

Note

An NPC only ever uses Unholster Humanoid Socket. The backpack pair, Unholster Backpack Socket and Use Unholster Backpack Socket, is read by the player only. A shotgun that rides on the player's backpack will sit on the body socket on an NPC, so give that socket a sensible transform on the NPC skeleton or the gun will hang in the wrong place.

How it fights with that gun¶

The distance an NPC opens fire at, how many rounds it puts in a burst, how badly it aims and how much it hurts you are all on the weapon's Data Asset, in its AI group: AI Engage Range, AI Preferred Range, AI Burst Count, AI Spread Multiplier, AI Damage Multiplier and AI Damage Multiplier to Player. Those fields and their shipped values are covered in Change how a gun feels to shoot.

The useful consequence: swapping Default Weapon Class changes how the NPC fights without touching the preset. A pistol NPC engages at 2000 and holds at 700, three rounds at a time. Hand the same NPC BP_Weapon_Shotgun_01 and it closes to 600, holds at 350 and fires one shot at a time, because those numbers came with the gun.

What stays on the NPC Data Asset is the movement side of a gunfight. All four presets ship the same values. Distances are in centimetres, times in seconds.

Field	Shipped	What it sets
`Aim Settle Time`	`0.35`	How long the NPC settles its aim before it shoots. Raise it to give the player more warning
`Strafe Distance`	`250`	How far sideways one strafe move goes
`Strafe Repick Interval`	`1.6`	How often a new strafe destination is chosen
`Strafe Repick Jitter`	`0.8`	Random spread added to that interval
`Ring Strafe Distance`	`120`	The same, for the tighter circling used close in
`Ring Repick Interval`	`1.2`	How often the close circle picks a new spot
`Ring Repick Jitter`	`0.6`	Random spread added to that interval
`Ring Snap Distance`	`250`	The distance at which circling takes over
`Retreat Distance`	`700`	How far the NPC backs off when you are too close
`Retreat Repath Interval`	`0.5`	How often the retreat path is recomputed

Every Repick Interval has a matching Jitter so a group of NPCs does not move on the same beat. Set the jitters to 0 and a squad steps in lockstep, which reads as robotic immediately.

Give that NPC a starting upgrade loadout¶

BP_NPCCharacter carries BP_WeaponUpgradeComponent, the same component the player has. On the NPC it ships empty, so a shipped NPC has a stock gun.

Open BP_NPCCharacter, or better a child of it if only some of your NPCs get upgrades.
Select BP_WeaponUpgradeComponent in the Components list.
Add one row to Initial Loadouts.
Set Weapon Class on that row to the same class you put in Default Weapon Class.
Add a row to Upgrades on that loadout. Set Upgrade to an upgrade Data Asset from Content/TheLastTemplate/Blueprints/DataAssets/Weapons/Upgrades/Childs/, and Current Level to which level of it the NPC has, starting at 1 for the first entry in that upgrade's Levels list.
Repeat step 3 for each weapon class, and step 5 for each upgrade on that weapon.
Compile and save.

One row of Initial Loadouts is one weapon class, so an NPC that can end up holding either a pistol or a shotgun gets two rows.

An upgrade an NPC does not have is simply left out of the array. Parts Item on the component can stay None: an NPC never pays for anything.

The upgrade assets themselves are the same ones the player crafts, and writing a new one is on Add a weapon upgrade.

Making a squad¶

Two knobs, two different scopes. Use whichever matches what actually differs.

What differs between your NPCs	Where you change it
The gun, the reserve, the patrol, the movement values	A Data Asset. Duplicate a preset per role and set `Data NPC` per placed actor
The starting upgrades	A child class of `BP_NPCCharacter`, because `Initial Loadouts` is on the component

So five NPCs with five different guns need five Data Assets and no new Blueprint. Five NPCs where one carries a silenced pistol need one extra child class.

Making your own pawn hold a gun¶

The short path is a child of BP_NPCCharacter. It arrives with everything already wired.

If you need a pawn that is not one, it has to carry BP_NPCWeaponManager and implement BPI_WeaponOwner. That interface is the whole contract between a gun and its holder: Get Equipped Weapon, Get Weapon Mesh, Get Aim Origin, Get Weapon Ammo, Can Fire Weapon, Consume Weapon Ammo, Consume Reserve Ammo and Add Weapon Ammo. It also needs BP_WeaponUpgradeComponent for upgrades to apply, and BP_AIBrain with an AI controller for anything to drive it. Childing BP_NPCCharacter is much less work for the same result.

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