BPC_AIPerceptionSystem — AI Perception System

Blueprint Spec — UE 5.5–5.7

Parent Class

ActorComponent

Dependencies

AI_BaseAgentController — Owner controller
BPC_AlertSystem — Alert level processing
DA_AIProfile — Perception config
Engine.AIPerception — UE5's UAIPerceptionComponent (or custom)

Purpose

Encapsulates all sensory perception for AI: sight, hearing, smell, and damage detection. Processes stimulus data, performs line-of-sight checks, applies detection modifiers (lighting, noise, movement speed), and reports findings to the owner AI_BaseAgentController. Supports configurable sensor ranges, cone angles, and stimulus decay rates.

Variables

Name	Type	Description
`SightRange`	Float	Maximum sight distance (cm)
`SightHalfAngle`	Float	Cone half-angle (degrees)
`SightLossHalfAngle`	Float	Peripheral angle before losing target
`HearingRange`	Float	Maximum hearing distance (cm)
`bUseSight`	Bool	Enable sight perception
`bUseHearing`	Bool	Enable hearing perception
`bUseDamageSense`	Bool	React to being damaged
`DetectionMultiplier_Lighting`	Float	0.5–2.0 based on ambient light
`DetectionMultiplier_Movement`	Float	1.0 standing, 0.3 crouched, 0.1 still
`DetectionMultiplier_Noise`	Float	Noise volume factor
`MaxAge`	Float	Seconds before stimulus decays
`SightDelay`	Float	Time before initial detection
`bTargetInSight`	Bool	Current LOS status
`LastSightTime`	Float	Last successful sight check
`RegisteredStimuli`	Array	Current active stimuli

Structs

Struct	Fields	Description
`FStimulusInfo`	Type: EStimulusType, Source: AActor, Location: FVector, Strength: Float, Age: Float, bCurrentlyValid: Bool	A perceived event

Enums

Enum	Values	Description
`EStimulusType`	Sight, Hearing, Damage, Smell, Vibration	Sensory channel

Functions

Name	Inputs	Outputs	Description
`InitializePerception`	Config: FPerceptionConfig	—	Set ranges, angles from profile
`OnSightStimulus`	Target: AActor	Bool	LOS check with modifiers
`OnHearingStimulus`	Location: FVector, NoiseTag: FGameplayTag, Loudness: Float	—	Sound detection
`OnDamageStimulus`	Instigator: AActor	—	Direct damage detection
`PerformLineOfSightCheck`	Target: AActor	Bool	Raycast with channel
`ApplyDetectionModifiers`	BaseChance: Float	Float	Apply darkness, movement, cover
`RegisterStimulus`	Info: FStimulusInfo	—	Add to active list
`ForgetStimulus`	Target: AActor	—	Clear specific source
`GetDominantStimulus`	—	FStimulusInfo	Highest priority active
`HasLineOfSightTo`	Target: AActor	Bool	Public wrapper
`GetSightStrength`	Target: AActor	Float	0.0–1.0 detection confidence
`DecayStimuli`	DeltaTime: Float	—	Age all stimuli

Event Dispatchers

Name	Parameters	Fired When
`OnTargetDetected`	Target: AActor, Strength: Float, Type: EStimulusType	New target detected
`OnTargetLost`	Target: AActor	Target out of perception
`OnLineOfSightChanged`	Target: AActor, bHasLOS: Bool	LOS state change
`OnSoundHeard`	Location: FVector, Loudness: Float	Sound detected

Blueprint Flow

[OnSightStimulus]
  └─► If !bUseSight → return false
  └─► If Distance > SightRange → return false
  └─► If Angle > SightHalfAngle → return false (outside cone)
  └─► // Modifier layer
         ModChance = ApplyDetectionModifiers(1.0)
         If Random < ModChance → return false (failed detection check)
  └─► // LOS check
         bHasLOS = PerformLineOfSightCheck(Target)
         If !bHasLOS → return false
  └─► // Confirmed
         Strength = CalculateStrength(Distance, Angle, Modifiers)
         FStimulusInfo = { Sight, Target, Location, Strength, 0, true }
         RegisterStimulus(Info)
         Broadcast OnTargetDetected(Target, Strength, Sight)
         Return true

[ApplyDetectionModifiers]
  └─► BaseChance *= DetectionMultiplier_Lighting (based on light channel)
  └─► BaseChance *= DetectionMultiplier_Movement (based on target velocity)
  └─► If target in cover → BaseChance *= 0.3 (partial cover) or 0.0 (full)
  └─► Return FMath::Clamp(BaseChance, 0.0, 1.0)

[PerformLineOfSightCheck]
  └─► Start = Owner Pawn EyeLocation
  └─► End = Target.GetActorLocation + Target BaseEyeHeight
  └─► Hit = LineTraceSingleByChannel(Channel = Visibility)
  └─► Return Hit.Actor == Target || Hit.Actor == nullptr

Stimulus Priority Table

Stimulus Type	Base Priority	Decay Rate	Triggers
Damage	100	Instant forget on lost	Combat state
Sight (Combat)	90	3 sec	Combat state
Sight (Suspicious)	60	8 sec	Suspicious state
Hearing (Loud)	50	5 sec	Investigate
Hearing (Quiet)	20	10 sec	Brief suspicion
Vibration	30	2 sec	Alert nearby

Communications With

Target	Method	Why
`AI_BaseAgentController`	Owner	Send stimulus results
`BPC_AlertSystem`	Get from Owner	Raise alerts based on perception
`BP_EnemyBase`	Owner Pawn	Check eye location, movement speed
World	Direct	Line trace queries
Audio Manager	Event	Query noise levels

Reuse Notes

Entirely data-driven via DA_AIProfile.PerceptionConfig
Detection modifiers allow stealth mechanics (darkness, crouch, cover)
Sight checks use UE5 AIPerception for stimulus system, but LOS logic is custom for accuracy
Hearing range accepts any gameplay-tagged noise source (footsteps, doors, gunshots)
Stimulus decay prevents infinite chase after target disappears
Renamed from BPC_PerceptionComponent to BPC_AIPerceptionSystem per Master naming convention.
Cross-references updated: BPC_AIControllerBase → AI_BaseAgentController.

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