Turn any grabbable object into a melee weapon¶

A melee weapon is a grabbed object with a BP_MeleeComponent on it, a melee Data Asset, and two sockets on its mesh. There is no attack key: you grab the object with Left Mouse and whip the mouse. No graph to open.

If you have not read How weapons work, start there. It also covers what your own actor needs to take the damage.

Melee Data Assets: Content/MPFriendslop/Blueprints/DataAssets/Melee/Childs/
The component: Content/MPFriendslop/Blueprints/ActorComponents/BP_MeleeComponent
The shipped weapons: Blueprints/Environments/Loot/Childs/BP_Loot_BaseballBat and BP_Loot_Hammer

What makes a strike¶

A grabbed loot item is pulled toward the point in front of your eyes. So when you turn your view fast, the object is dragged through the air, and that is the swing. Three checks decide whether it hits:

A swing. Your view must turn by at least Swing Turn Speed times Swing Turn Window degrees within Swing Turn Window seconds, in any direction. With the shipped values, that is 30 degrees in a tenth of a second. The swing then stays open for Swing Duration seconds after the last fast turn.
A fast tip. While the swing is open, the component measures the speed of the StrikeEnd socket, in centimetres per second, relative to you. Outside a swing, that speed counts as zero.
A hit. From Min Strike Speed, and once Strike Cooldown has passed since the last hit, the zone between the two sockets is swept with spheres of Strike Radius. Each actor it touches whose object type is in Strike Object Types is hit once. The weapon never hits itself or the player who holds it.

This is why walking does nothing. Without a fast turn of the view there is no swing. And your own movement is removed from the tip speed, so running into someone adds nothing to the hit. Picking the object up does not whoosh or strike either.

The faster the tip, the harder the hit. The strength of a hit runs from 0 at Min Strike Speed to 1 at Max Strike Speed, and the damage, the push, the hit sound and the camera shake all follow it.

Before you start¶

You need an object that can already be grabbed. The simplest is a loot item, a child of BP_LootBase: see Add a loot item. For an actor of your own, see Make any actor grabbable first.

Step 1, the strike sockets¶

The strike zone is the segment between two sockets on the mesh.

Open your static mesh and open the Socket Manager.
Add a socket named StrikeStart where the hitting part begins.
Add a socket named StrikeEnd at the tip. The tip speed is measured on this one.

On SM_Loot_BaseballBat, StrikeStart is at (0, 0, 52) and StrikeEnd at (0, 0, 78): the last part of the bat. On SM_Loot_Hammer, the two sockets sit on each side of the head.

Warning

If no mesh on the actor has a socket with the name in Strike Start Socket, or if Melee Data is empty, the component switches itself off. You can still grab and carry the object, but it never whooshes and never hits. There is no error.

Step 2, the melee Data Asset¶

In Blueprints/DataAssets/Melee/Childs/, duplicate DA_Melee_BaseballBat or DA_Melee_Hammer.
Name it after your weapon, for example DA_Melee_Crowbar.
Open it. Every field already holds a working value, so you replace rather than fill in.

The swing, in Settings|Swing

Field	What it does	Bat	Hammer
`Swing Turn Speed`	How fast the view must turn to count as a swing, in degrees per second	`300`	`300`
`Swing Turn Window`	Time over which that turn is measured, in seconds	`0.1`	`0.1`
`Swing Duration`	How long the swing stays open after the last fast turn, in seconds	`0.3`	`0.3`

The strike, in Settings|Strike

Field	What it does	Bat	Hammer
`Strike Start Socket`	Socket where the strike zone begins	`StrikeStart`	`StrikeStart`
`Strike End Socket`	Socket at the tip, where the zone ends	`StrikeEnd`	`StrikeEnd`
`Strike Radius`	Radius of the spheres swept along the zone	`5`	`4.5`
`Strike Cooldown`	Shortest time between two hits, in seconds	`0.4`	`0.35`
`Strike Object Types`	What the weapon can hit	`Pawn`, `PhysicsBody`	`Pawn`, `PhysicsBody`

If you named your sockets something else in Step 1, type those names here.

The damage, in Settings|Damage

Field	What it does	Bat	Hammer
`Min Strike Speed`	Tip speed below which nothing is hit	`250`	`200`
`Max Strike Speed`	Tip speed that gives a full-strength hit	`900`	`700`
`Min Damage`	Damage at `Min Strike Speed`	`10`	`12`
`Max Damage`	Damage at `Max Strike Speed` and above	`35`	`30`
`Knockback`	Speed given to the victim by a full-strength hit, along the swing, in centimetres per second. A character is launched, a physics object is pushed	`450`	`300`

The hammer is the easier one to use: it hits from 200 and reaches full strength at 700. The bat needs a faster swing and hits harder at full strength.

The sound, in Settings|Audio

Field	What it does	Bat	Hammer
`Whoosh Speed`	Tip speed at which the whoosh plays, once each time the tip goes past it	`450`	`450`
`Whoosh Cooldown`	Shortest time between two whooshes, in seconds	`0.4`	`0.35`
`Whoosh Sound`	The swing through the air, played at the tip	`CUE_Melee_Whoosh`	`CUE_Melee_Whoosh`
`Heavy Strike Ratio`	Strength from which the heavy sound plays instead of the light one	`0.6`	`0.6`
`Light Strike Sound`	A weak hit	`CUE_Melee_Hit_Light`	`CUE_Melee_Hit_Light`
`Heavy Strike Sound`	A strong hit	`CUE_Melee_Hit_Heavy`	`CUE_Melee_Hit_Heavy`

The feedback, in Settings|Effects

Field	What it does	Bat	Hammer
`Strike FX`	Niagara system spawned at the point of impact, facing out of the surface	`NS_Weapon_Impact`	`NS_Weapon_Impact`
`Camera Shake`	Shake on the holder's camera when they hit, from half to full scale with the strength	`CS_MeleeStrike`	`CS_MeleeStrike`

The strength of the shake itself is on CS_MeleeStrike in Blueprints/Effects/. Duplicate it if your weapon should kick differently.

Step 3, the component¶

Open your actor Blueprint.
In Components, click Add and pick BP_MeleeComponent.
In its Details, in Settings|Melee, set Melee Data to your Data Asset.
Compile and save.

Melee Data is the only field on the component. BP_Loot_Hammer is the model: a loot child with a BP_MeleeComponent whose Melee Data is DA_Melee_Hammer.

On your own actor¶

If your actor is not a child of BP_LootBase, it must implement BPI_Grabbable. That includes GetGrabHolder: the component asks that function who holds the object, and expects a pawn. If it returns nothing, the weapon finds no holder and deals no damage. Return the holder from a Replicated variable, as BP_LootBase does with Current Holder.

The component uses the first mesh on the actor that has the Strike Start Socket. So on an actor with several meshes, put the sockets on the one that moves with the hit.

Your character needs nothing for melee beyond being able to grab. The component reads the aim and the movement of whichever pawn GetGrabHolder returns.

Two limits worth knowing¶

An inventory item in your hand cannot be swung. Only a grabbed object can be a melee weapon.
A victim takes the damage and the push. There is no hit reaction animation.

To make the object easier or harder to carry and swing, see How grabbing works, and tuning the weight.

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