[C++/UE] UE5中AI開發的一點功能梳理（五） – AI Perception 感知系統 Sense部分

//AIPerceptionSystem
UAIPerceptionSystem::UAIPerceptionSystem(const FObjectInitializer& ObjectInitializer)
    : Super(ObjectInitializer)
    , PerceptionAgingRate(0.3f)
    , bHandlePawnNotification(false)
    , NextStimuliAgingTick(0.)
    , CurrentTime(0.)
{
    StimuliSourceEndPlayDelegate.BindDynamic(this, &UAIPerceptionSystem::OnPerceptionStimuliSourceEndPlay);
}

void UAIPerceptionSystem::Tick(float DeltaSeconds)
{
    SCOPE_CYCLE_COUNTER(STAT_AI_PerceptionSys);
    SCOPE_CYCLE_COUNTER(STAT_AI_Overall);
    CSV_SCOPED_TIMING_STAT_EXCLUSIVE(AIPerception);
    // if no new stimuli
    // and it's not time to remove stimuli from "know events"

    UWorld* World = GEngine->GetWorldFromContextObjectChecked(GetOuter());
    check(World);

    if (World->bPlayersOnly == false)
    {
        // cache it
        CurrentTime = World->GetTimeSeconds();      
        if (SourcesToRegister.Num() > 0)
        {
            PerformSourceRegistration();
        }
        bool bSomeListenersNeedUpdateDueToStimuliAging = false;
        if (NextStimuliAgingTick <= CurrentTime)
        {
            constexpr double Precision = 1./64.;
            const float AgingDt = FloatCastChecked<float>(CurrentTime - NextStimuliAgingTick, Precision);
            bSomeListenersNeedUpdateDueToStimuliAging = AgeStimuli(PerceptionAgingRate + AgingDt);
            NextStimuliAgingTick = CurrentTime + PerceptionAgingRate;
        }
        //...
    }
}

bool UAIPerceptionSystem::AgeStimuli(const float Amount)
{
    ensure(Amount >= 0.f);
    bool bTagged = false;

    for (AIPerception::FListenerMap::TIterator ListenerIt(ListenerContainer); ListenerIt; ++ListenerIt)
    {
        FPerceptionListener& Listener = ListenerIt->Value;
        if (Listener.Listener.IsValid())
        {
            // AgeStimuli will return true if this listener requires an update after stimuli aging
            if (Listener.Listener->AgeStimuli(Amount))
            {
                Listener.MarkForStimulusProcessing();
                bTagged = true;
            }
        }
    }
    return bTagged;
}

//AIPerceptionComponent.cpp
bool UAIPerceptionComponent::AgeStimuli(const float ConstPerceptionAgingRate)
{
    bool bExpiredStimuli = false;

    for (FActorPerceptionContainer::TIterator It(PerceptualData); It; ++It)
    {
        FActorPerceptionInfo& ActorPerceptionInfo = It->Value;

        for (FAIStimulus& Stimulus : ActorPerceptionInfo.LastSensedStimuli)
        {
            // Age the stimulus. If it is active but has just expired, mark it as such
            if (Stimulus.AgeStimulus(ConstPerceptionAgingRate) == false
                && (Stimulus.IsActive() || Stimulus.WantsToNotifyOnlyOnPerceptionChange())
                && Stimulus.IsExpired() == false)
            {
                AActor* TargetActor = ActorPerceptionInfo.Target.Get();
                if (TargetActor)
                {
                    Stimulus.MarkExpired();
                    RegisterStimulus(TargetActor, Stimulus);
                    bExpiredStimuli = true;
                }
            }
        }
    }

    return bExpiredStimuli;
}

//AIPerceptionTypes.h
/** @return false when this stimulus is no longer valid, when it is Expired */
FORCEINLINE bool AgeStimulus(float ConstPerceptionAgingRate) 
{ 
    Age += ConstPerceptionAgingRate; 
    return Age < ExpirationAge;
}