Core Components Reference

Documentation Unreal Engine AI Reference

Technical reference for MovementEvaluator, ActionEvaluation, ThreatDetection, and MeleeTrace components.

UMovementEvaluatorComponent

Purpose: Handles tactical positioning, distance maintenance, strafing, and avoidance.

Key Properties

// Distance Management
UPROPERTY(EditAnywhere, Category = "Movement")
float IdealMinDistance = 200.f;
 
UPROPERTY(EditAnywhere, Category = "Movement")
float IdealMaxDistance = 400.f;
 
// Strafing
UPROPERTY(EditAnywhere, Category = "Strafe")
float StrafeRadius = 300.f;
 
UPROPERTY(EditAnywhere, Category = "Strafe")
float StrafeDuration = 3.f;
 
UPROPERTY(EditAnywhere, Category = "Strafe")
float StrafeCooldown = 2.f;
 
// Navigation
UPROPERTY(EditAnywhere, Category = "Navigation")
float DirectControlThreshold = 600.f;
 
// Debug
UPROPERTY(EditAnywhere, Category = "Debug")
bool bDebugLog = false;

Key Functions

// Called each tick to get movement direction
FVector EvaluateMovement(const FVector& TargetLocation, float DeltaTime);
 
// Apply behavior preset
void ApplyBehaviorConfig(const FMovementBehaviorConfig& Config);
void ApplyBehaviorProfile(UMovementBehaviorProfile* Profile);
 
// Manual overrides
void SetDesiredDistance(float Min, float Max);
void EnableStrafing(bool bEnable);

Behavior Presets

// Aggressive close-range fighter
FMovementBehaviorConfig::MakeAttacker();
 
// Patient mid-range combatant
FMovementBehaviorConfig::MakeWaiter();
 
// Flanking enemy that circles wide
FMovementBehaviorConfig::MakeFlanker();
 
// Defensive enemy that keeps distance
FMovementBehaviorConfig::MakeCoward();

Usage Example

// In BeginPlay of AI Controller:
MovementEvaluator->ApplyBehaviorConfig(
    FMovementBehaviorConfig::MakeAttacker()
);
 
// Or use data asset:
MovementEvaluator->ApplyBehaviorProfile(AggressiveMeleeProfile);

UActionEvaluationComponent

Purpose: Scores and selects actions, manages cooldowns, executes abilities or BT sequences.

Key Properties

UPROPERTY(EditAnywhere, Category = "Actions")
UActionSet* CurrentActionSet;
 
UPROPERTY(EditAnywhere, Category = "Scoring")
float NoveltyDecayRate = 0.2f;
 
UPROPERTY(EditAnywhere, Category = "Debug")
bool bDebugLog = false;

Key Functions

// Evaluate all actions and return best
FChosenAction EvaluateBestAction(const FDecisionContext& Context);
 
// Manually execute an action
void ExecuteAction(const FChosenAction& Action, AActor* TargetActor);
 
// Swap action set at runtime (e.g., boss phase 2)
void SetActionSet(UActionSet* NewSet);
 
// Notify when action ends (auto-called by SEC.Action.End event)
void NotifyActionCommitted(FGameplayTag AbilityTag, double NowSeconds);
 
// Add runtime modifiers
void AddRuntimeModifier(FGameplayTag ActionTag, float BonusWeight);
void ClearRuntimeModifiers();

Scoring Formula

FinalScore = BaseWeight
           × DistanceScore        // 0-1 from FRangeEval
           × AngleScore           // 0-1 from FRangeEval
           × HealthModifiers      // From context tags
           × NoveltyScore         // Decays if used recently
           × ChainBonus           // If valid combo
           × RuntimeModifiers     // Dynamic adjustments

Usage Example

// In StateTree task or Blueprint:
FDecisionContext Context = BuildContext();
FChosenAction BestAction = ActionEvaluation->EvaluateBestAction(Context);
 
if (BestAction.IsValid())
{
    ActionEvaluation->ExecuteAction(BestAction, TargetActor);
}

UThreatDetectionComponent

Purpose: Tracks player camera attention, adjusts behavior when under observation.

Key Properties

UPROPERTY(EditAnywhere, Category = "Threat")
float AttentionDecayRate = 0.5f;
 
UPROPERTY(EditAnywhere, Category = "Threat")
float DetectionAngle = 45.f;
 
UPROPERTY(EditAnywhere, Category = "Threat")
float MinThreatForReaction = 0.6f;

Key Functions

// Current threat level [0-1]
float GetThreatLevel() const;
 
// Is player looking at this AI?
bool IsPlayerLookingAtMe() const;
 
// Manually add threat
void AddThreat(float Amount);

How It Works

Detects when player camera points at AI (cone check)
Threat level builds up while under observation
Decays over time when not observed
Feeds into action scoring (defensive actions score higher when threatened)
Can trigger strafe direction changes

USECMeleeTraceComponent

Purpose: Frame-rate independent swept traces for melee combat.

Key Functions

// Register weapon's trace sockets (auto-called on equip)
void RegisterWeaponTraceSockets(const TArray<FSECTraceSocket>& Sockets);
 
// Start tracing specific sockets (called by notify state)
void BeginTrace(const TArray<FName>& SocketIDs);
 
// Stop tracing
void EndTrace(const TArray<FName>& SocketIDs);
 
// Set damage for current traces
void SetDamageConfig(USECDamageConfig* Config);

Trace Shapes

enum class ESECTraceShape
{
    Sphere,            // Single point sphere sweep
    Capsule,           // Single point capsule sweep
    CapsuleTwoPoint    // Capsule between two sockets (for blades)
};

How It Works

Weapon registers trace sockets on equip
Animation montage includes SECMeleeTraceNotifyState
Notify state calls BeginTrace with socket IDs
Component stores previous frame positions
Performs swept traces from previous to current positions
On hit, applies damage via Gameplay Effect
Prevents multi-hit on same actor (configurable interval)

Usage: Fully automatic - just configure weapon sockets and add notify states to montages.