Why does my Unreal AI not detect the player?

Detected actors need an AIPerceptionStimuliSourceComponent registered for the relevant sense (Sight, Hearing). Add the component to the player and call RegisterForSense for AISense_Sight. Also confirm the AI's perception component has the matching Sense Config and the Detection By Affiliation flags.

How do I configure AI Perception to detect by team?

In the AIPerceptionComponent's Sense Config (Sight), check Detect Enemies/Neutrals/Friendlies as needed. Set the AI's team via IGenericTeamAgentInterface. The perception filters detections by team affiliation.

Why does perception only detect on the server?

AI Perception runs only on the authority. Clients see no perception state. For client-side hints (visual indicators), replicate relevant data via RPC or RepNotify rather than relying on perception client-side.

Fix: Unreal AI Perception Stimulus Source Not Registered

Quick answer: Add an AIPerceptionStimuliSourceComponent to detected actors and call RegisterForSense(UAISense_Sight::StaticClass()). The AI’s AIPerceptionComponent needs a matching Sense Config with the right affiliation flags.

Here is how to fix Unreal AI Perception failing to detect actors that should be in line of sight. Detection requires both perception and stimulus source registration; either side missing means no detection.

The Symptom

AI character has Sight sense configured. Player walks into view; OnPerceptionUpdated never fires. AI does not react.

What Causes This

No stimulus source. Perceived actors need to register as a stimulus source for each sense.

Affiliation mismatch. Sight Config has Detect Enemies / Neutrals / Friendlies flags. If none of these match the player’s team, no detection.

Sight radius too small. Default sight radius may not cover the player.

The Fix

Step 1: Add stimulus source on the player.

// In APlayerCharacter constructor
StimuliSource = CreateDefaultSubobject<UAIPerceptionStimuliSourceComponent>(TEXT("StimuliSource"));
StimuliSource->RegisterForSense(UAISense_Sight::StaticClass());
StimuliSource->RegisterForSense(UAISense_Hearing::StaticClass());
StimuliSource->bAutoRegister = true;

Step 2: Configure AI’s perception. On the AIController, add AIPerceptionComponent. Add a SightConfig:

SightConfig:
  SightRadius:               2000
  LoseSightRadius:           2200
  PeripheralVisionAngle:     90
  DetectionByAffiliation:
    DetectEnemies:           true
    DetectNeutrals:          true
    DetectFriendlies:        false

Step 3: Set up team affiliation.

// In APlayerController
virtual FGenericTeamId GetGenericTeamId() const override
{
    return FGenericTeamId(0);   // player team
}

// In AAIController
virtual FGenericTeamId GetGenericTeamId() const override
{
    return FGenericTeamId(1);   // enemy team
}

Step 4: Subscribe to perception events.

PerceptionComp->OnPerceptionUpdated.AddDynamic(this, &AMyAI::OnPerceptionUpdated);

void AMyAI::OnPerceptionUpdated(const TArray<AActor*>& UpdatedActors)
{
    for (AActor* a : UpdatedActors)
    {
        UE_LOG(LogTemp, Log, TEXT("Detected: %s"), *a->GetName());
    }
}

Step 5: Verify with showdebug ai. The on-screen overlay shows perception cones, sight rays, and detection state. Walk the player into view and watch for confirmation.

“Stimulus source on detected. Perception config on AI. Affiliations match. Detection fires.”

Related Issues

For Anim Notify state, see Anim Notify End. For multicast RPC, see Multicast RPC.

Stimulus source. Perception config. Team setup. AI sees the player.