UE AIPerception感知非Pawn对象

原理部分

AI之所以只感知Pawn，是因为被感知的对象需要手动注册，而非全局搜索。

检索已存在Pawn

在BeginPlay阶段，为所有的AISense，调用RegisterAllPawnsAsSourcesForSense

UWorld::BeginPlay()
	GetAISystem()->StartPlay();
void UAISystem::StartPlay()
	PerceptionSystem->StartPlay();
void UAIPerceptionSystem::StartPlay()
	for (UAISense* Sense : Senses)
	{
		if (Sense != nullptr && Sense->ShouldAutoRegisterAllPawnsAsSources())
		{
			FAISenseID SenseID = Sense->GetSenseID();
			RegisterAllPawnsAsSourcesForSense(SenseID);
		}
	}
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并且之后再通过RegisterSenseClass新注册的AISense，也会调用RegisterAllPawnsAsSourcesForSense

FAISenseID UAIPerceptionSystem::RegisterSenseClass(TSubclassOf<UAISense> SenseClass)
	FAISenseID SenseID = UAISense::GetSenseID(SenseClass);
	if (Senses[SenseID] == nullptr)
		Senses[SenseID] = NewObject<UAISense>(this, SenseClass);
		if (Senses[SenseID]->ShouldAutoRegisterAllPawnsAsSources())
			World->GetTimerManager().SetTimerForNextTick(FTimerDelegate::CreateUObject(this, &UAIPerceptionSystem::RegisterAllPawnsAsSourcesForSense, SenseID));
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RegisterAllPawnsAsSourcesForSense则是检索所有的Pawn进行注册

for (TActorIterator<APawn> PawnIt(World); PawnIt; ++PawnIt)
{
	RegisterSource(SenseID, **PawnIt);
}
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处理新生成的Pawn

在UAISystem::PostInitProperties()内，注册了Actor生成的委托

if (WorldOuter)
{
	FOnActorSpawned::FDelegate ActorSpawnedDelegate = FOnActorSpawned::FDelegate::CreateUObject(this, &UAISystem::OnActorSpawned);
	ActorSpawnedDelegateHandle = WorldOuter->AddOnActorSpawnedHandler(ActorSpawnedDelegate);
}
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而在void UAISystem::OnActorSpawned(AActor* SpawnedActor)内，就判断如果生成的是Pawn，感知系统会进行添加

APawn* AsPawn = Cast<APawn>(SpawnedActor);
if (AsPawn)
{
	PerceptionSystem->OnNewPawn(*AsPawn);
}
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在void UAIPerceptionSystem::OnNewPawn(APawn& Pawn)内，对于每个AISense，如果bAutoRegisterAllPawnsAsSources为true，则进行注册

for (UAISense* Sense : Senses)
{
	if (Sense->ShouldAutoRegisterAllPawnsAsSources())
	{
		FAISenseID SenseID = Sense->GetSenseID();
		RegisterSource(SenseID, Pawn);
	}
}
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注册Pawn

void UAIPerceptionSystem::RegisterSource(FAISenseID SenseID, AActor& SourceActor)则是先把要注册的信息添加到SourcesToRegister内

SourcesToRegister.AddUnique(FPerceptionSourceRegistration(SenseID, &SourceActor));
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之后在Tick时进行处理

UAIPerceptionSystem::PerformSourceRegistration()
	Senses[PercSource.SenseID]->RegisterSource(*SourceActor);
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以Sight为例

void UAISense_Sight::RegisterSource(AActor& SourceActor)
bool UAISense_Sight::RegisterTarget(AActor& TargetActor, const TFunction<void(FAISightQuery&)>& OnAddedFunc /*= nullptr*/)
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通过FAISenseAffiliationFilter::ShouldSenseTeam判断是否是需要检测的目标，注意若没有继承IGenericTeamAgentInterface，则视为中立方，需要勾选Sense Config的DetectNeutrals

感知非Pawn对象

综上所述，我们只需要对已经生成的对象和新生成的对象，对于UAIPerceptionSystem的所有Sense，调用RegisterSource即可。

RegisterSource有一个是内部版本，参数是RegisterSource(FAISenseID SenseID, AActor& SourceActor)，这个是内部使用的。我们只需要调用包装好的版本：

template<typename FSenseClass>
void RegisterSource(AActor& SourceActor);

/** Registers given actor as a source for all registered senses */
void RegisterSource(AActor& SourceActor);

void RegisterSourceForSenseClass(TSubclassOf<UAISense> Sense, AActor& Target);
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并且注册后就不用管了，因为已经在EndPlay时绑定了UnregisterSource函数

void UAIPerceptionSystem::PerformSourceRegistration()
	for (const FPerceptionSourceRegistration& PercSource : SourcesToRegister)
		SourceActor->OnEndPlay.AddUnique(StimuliSourceEndPlayDelegate);
		
StimuliSourceEndPlayDelegate.BindDynamic(this, &UAIPerceptionSystem::OnPerceptionStimuliSourceEndPlay);

void UAIPerceptionSystem::OnPerceptionStimuliSourceEndPlay(AActor* Actor, EEndPlayReason::Type EndPlayReason)
{
	UnregisterSource(*Actor);
}
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