Melee Trace

Documentation Unreal Engine AI Melee Combat

Frame-rate independent swept weapon traces with per-window damage configs and ISECDamageable integration.

Each active frame, USECMeleeTraceComponent sweeps from the last socket positions to the current ones. Fast swings still register hits at 30 or 144 FPS.

Viewport

Interpolation OFF

LVL_SEC_Showcase>Melee Trace

Swing Speed60°

SIM_FPS: 10

STATUS: TUNNELING

Successful Hits

Without Interpolation: The fast sword swings 'teleport' over the target between frames, causing a miss.

When to Use This

Melee on AI or player pawns.
Swings that outrun per-frame overlap checks.
Several hit zones on one weapon (blade, pommel).
Different damage per montage window through SECDamageConfig.

AEnemyCharacterBase ships with USECMeleeTraceComponent. Add SEC Melee Trace to any other pawn you want in the pipeline.

Register trace sockets on the wielder (usually when the weapon equips). StartTracing captures socket positions and enables tick. Each tick sub-steps between previous and current transforms and sweeps sphere, capsule, or two-point capsule shapes (SubStepDistance, MaxSubSteps).

Shape	Use
Sphere	Fists, small contact points.
Capsule	Single-socket volume aligned to bone rotation.
CapsuleTwoPoint	Span between two mesh sockets (typical sword blade).

The first tick after StartTracing records positions only; sweeps begin once a previous sample exists.

Hit order:

TeamFilter and duplicate checks (CanHitActor, owner ignored).
OnMeleeHit with FMeleeHitData (contact VFX/SFX hook).
ISECDamageable: BuildDamageInfo → ApplyDamage → HandleDamageResult → OnMeleeHitResponse.
No interface: RecordHit, ApplyPointDamage (CurrentDamage, DamageTypeClass), OnMeleeHitResponse with bDamageApplied = true.

StartTracing and tick body return early without authority. StopTracing clears active sockets, hit records, and disables tick.

Setup

1. Component on the wielder

Details

SEC Melee Trace Component (SECMeleeTraceComponent)

Damage

Default Damage Config

None

Base Damage

Hit Reset Interval

Team Filter

No Filter

Trace

Sub Step Distance

Max Sub Steps

Debug

Draw Debug

Debug Draw Duration

0.1

Default component on the enemy pawn. Add SEC Melee Trace to other wielders manually.

Set Default Damage Config or Base Damage when a notify omits damage.

2. Weapon mesh sockets

Add sockets on the weapon mesh (example: blade_start, blade_end).

3. Weapon Blueprint

Subclass ASECWeaponBase, fill TraceSockets. OnEquipped assigns SourceComponent to the weapon mesh and calls RegisterTraceSocket_Struct on the wielder's trace component.

Details

Weapon Trace Socket (FSECTraceSocket)

SEC|Weapon

Attach Socket

hand_r

SEC|Trace

Blade

Shape

Capsule Two Point

Socket Or Bone Name

blade_start

End Socket Or Bone Name

blade_end

Radius

Trace Channel

Pawn

One TraceSockets array entry on the weapon Blueprint. OnEquipped registers sockets on the wielder trace component.

Per-attack damage comes from the montage notify or component default, not the weapon actor.

4. Damage config

Create SECDamageConfig, assign on the notify or Default Damage Config:

Details

SEC Damage Config (SECDamageConfig)

Damage

Damage Type

None

Forces

Hit Bone Force

Hit Overall Force

Hit Rotational Force

Data asset assigned on the montage notify or the trace component Default Damage Config.

Per window: notify Damage Config → Default Damage Config → Base Damage. StartTracingSimple accepts a numeric override; values below zero fall back to Base Damage.

5. Montage window

Add Notify State → SEC Melee Trace Window on strike frames:

Details

SEC Melee Trace Window (SECMeleeTraceNotifyState)

Melee Trace

Socket IDs

1 Array element

Damage Config

DA_SwordDamage

Debug

Enable Debug Draw

Anim notify state on strike frames. Empty Socket IDs activates every registered socket.

Empty Socket IDs activates every registered socket. Names must match each trace socket ID.

Animation montage with SEC Melee Trace Window notify state

Equip, play the montage: register on equip, StartTracing at notify begin, StopTracing at notify end.

Integration

System	Link
Reaction System	`ApplyDamage` returns `ResultTags` for reaction selection.
Multiplayer	Trace and damage on authority; clients follow replicated state.
Configuration Reference	Shared project tuning (reconcile damage fields with this page).

TeamFilter on the trace component (damage gating, not combat target selection):

Details

SEC Melee Trace Component (SECMeleeTraceComponent)

Damage

Team Filter

No Filter

Damage category on the wielder trace component. Filters who can be hit, separate from combat target selection.

AdvancedDelegates and manual control

void StartTracing(const TArray<FName>& SocketIDs, USECDamageConfig* DamageConfig = nullptr, bool bDebugOverride = false);
void StartTracingSimple(const TArray<FName>& SocketIDs, float DamageOverride);
void StopTracing();
 
void RegisterTraceSocket_Struct(const FSECTraceSocket& TraceSocket);
void UnregisterTraceSocket(FName ID);
void UnregisterAllSockets();  // weapon swap: stock OnUnequipped does not call this

OnMeleeHit: FMeleeHitData (HitResult, FromSocketID, DamageConfig).

OnMeleeHitResponse: FMeleeHitData + FSECDamageResult.

Subclass BuildDamageInfo or HandleDamageResult for crit scaling, pierce, or custom hit recording.

Blueprint helpers: RegisterSphereSocket, RegisterCapsuleSocket, RegisterTwoPointCapsule.

AdvancedISECDamageable pipeline

FSECDamageInfo: Instigator, HitResult, HitDirection, DamageDefinition (ToDamageDefinition() when a config is active).

FSECDamageResult: bDamageApplied, ResultTags.

HandleDamageResult recording:

Result	Recording
`bDamageApplied = true`	`RecordHit` (blocks repeat hits this window when `HitResetInterval` is 0).
`bDamageApplied = false`, tags match `SkipRecordTags`	No record (dodge: try again next frame).
`bDamageApplied = false`, other tags	`RecordHit` (parry/block consumes the swing).
`bDamageApplied = false`, empty tags	No record (ignored stimulus).

HitResetInterval: 0 allows one recorded hit per target per window. Above 0, the same target can register again after that many seconds; expired records purge each tick.

AdvancedDebug

SEC.Debug.Melee.DrawTracing 1

Component Draw Debug, or notify Enable Debug Draw for one window (bSessionDebugOverride).

AdvancedCommon issues

Problem	Likely cause	Fix
No hits	`SocketIDs` ≠ socket `ID`	Match `FName` strings.
No hits	Sockets missing	Equip via `ASECWeaponBase::OnEquipped`; wielder needs trace component.
Miss first active frame	Warm-up tick	Normal: sweep needs a prior position sample.
Through walls	`TraceChannel`	Pick a channel blocked by world geometry.
Two hits one swing	Two sockets touch	Expected; narrow active `SocketIDs` or shapes.
No damage on SEC pawn	No interface	Implement `ISECDamageable`.
Client swing, no damage	No authority	`StartTracing` / tick skip non-authority owners.