[C++/UE] UE5中AI開發的一點功能梳理（五） – AI Perception 感知系統 Sense部分
感知系統AI Perception
- 使用的AI Controller -> Add Component
- AIPerception => 刺激源接收器
- AIPerception Stimuli Source => 刺激源發生器
- 在非AI Actor上添加並注冊對應事件，從而被AI所「感知」到
- 增加具體要被哪些感官所能感知到
- 所有Pawn都會默認加上Sight，所以多用於添加其他類型的刺激或者非Pawn的Actor也能發生刺激的場景上
- 在非AI Actor上添加並注冊對應事件，從而被AI所「感知」到
AI Perception使用及參數說明
- 在AI Perception組件中，可以配置相應的Sense Config項
Sight 視覺感知
- Detection by Affiliation 決定誰能觸發事件（敵人/路人/友軍）
- Affiliation目前只能在C++裡定義
- 在blueprint裡可以勾上Dectect Neutrals（路人）來檢測所有Actor
- Auto Success Range from Last Seen Location 對象必然會被重新看見的距離
- if value > 0，對象如果離上次被看見的距離 < value，則仍然算是被看見
- if value < 0，每次失蹤後都要重新做一次完整的視覺感知
- 例子：解決恐怖遊戲的當面入櫃情況
- 具體視野計算
- Sight Radius / Lose Sight Radius 視野/ 失蹤距離，會被轉化成Square值
//AISense_Sight.cpp
UAISense_Sight::FDigestedSightProperties::FDigestedSightProperties(const UAISenseConfig_Sight& SenseConfig)
{
SightRadiusSq = FMath::Square(SenseConfig.SightRadius + SenseConfig.PointOfViewBackwardOffset);
LoseSightRadiusSq = FMath::Square(SenseConfig.LoseSightRadius + SenseConfig.PointOfViewBackwardOffset);
}-
- Peripheral Vision Half Angle Degrees 可視範圍的半角，會被轉成弧度加入計算
- Point of View Backward Offset 如果不接近於0，就會用來調整視野的起點位置
- == 0：起點位置 = AI自身的位置
- != 0：起點位置 = 正後方方向normalized * Point of View Backward Offset
- Near clipping Radius：從新起點計算的近平面半徑，會被轉化為Square值
- Point of View Backward Offset 如果不接近於0，就會用來調整視野的起點位置
- Peripheral Vision Half Angle Degrees 可視範圍的半角，會被轉成弧度加入計算
//AISense_Sight.cpp
UAISense_Sight::FDigestedSightProperties::FDigestedSightProperties(const UAISenseConfig_Sight& SenseConfig)
{
NearClippingRadiusSq = FMath::Square(SenseConfig.NearClippingRadius);
}-
- 具體視野示意圖如下（視野檢測會調用CheckIsTargetInSightCone）：
//AIHelpers.cpp
//----------------------------------------------------------------------//
// CheckIsTargetInSightCone
// F
// *****
// * *
// * *
// * *
// * *
// * *
// /
// /
// /
// X /
// /
// *** /
// * N * /
// * * /
// N N
//
//
//
//
//
//
// B
//
// X = StartLocation
// B = Backward offset
// N = Near Clipping Radius (from the StartLocation adjusted by Backward offset)
// F = Far Clipping Radius (from the StartLocation adjusted by Backward offset)
//----------------------------------------------------------------------//
bool CheckIsTargetInSightCone(const FVector& StartLocation, const FVector& ConeDirectionNormal, float PeripheralVisionAngleCos,
float ConeDirectionBackwardOffset, float NearClippingRadiusSq, float const FarClippingRadiusSq, const FVector& TargetLocation)
{
const FVector BaseLocation = FMath::IsNearlyZero(ConeDirectionBackwardOffset) ? StartLocation : StartLocation - ConeDirectionNormal * ConeDirectionBackwardOffset;
const FVector ActorToTarget = TargetLocation - BaseLocation;
const FVector::FReal DistToTargetSq = ActorToTarget.SizeSquared();
if (DistToTargetSq <= FarClippingRadiusSq && DistToTargetSq >= NearClippingRadiusSq)
{
// Will return true if squared distance to Target is smaller than SMALL_NUMBER
if (DistToTargetSq < SMALL_NUMBER)
{
return true;
}
// Calculate the normal here instead of calling GetUnsafeNormal as we already have the DistToTargetSq (optim)
const FVector DirectionToTargetNormal = ActorToTarget * FMath::InvSqrt(DistToTargetSq);
return FVector::DotProduct(DirectionToTargetNormal, ConeDirectionNormal) > PeripheralVisionAngleCos;
}
return false;
}
//AISense_Sight.cpp
UAISense_Sight::EVisibilityResult UAISense_Sight::ComputeVisibility(UWorld* World, FAISightQuery& SightQuery, FPerceptionListener& Listener, const AActor* ListenerActor, FAISightTarget& Target, AActor* TargetActor, const FDigestedSightProperties& PropDigest, float& OutStimulusStrength, FVector& OutSeenLocation, int32& OutNumberOfLoSChecksPerformed, int32& OutNumberOfAsyncLosCheckRequested) const
{
//...
const FVector TargetLocation = TargetActor->GetActorLocation();
const float SightRadiusSq = SightQuery.GetLastResult() ? PropDigest.LoseSightRadiusSq : PropDigest.SightRadiusSq;
if (!FAISystem::CheckIsTargetInSightCone(Listener.CachedLocation, Listener.CachedDirection, PropDigest.PeripheralVisionAngleCos, PropDigest.PointOfViewBackwardOffset, PropDigest.NearClippingRadiusSq, SightRadiusSq, TargetLocation))
{
return EVisibilityResult::NotVisible;
}
//...
}Hearing 聽覺感知
- 響應Report Noise Event
- blueprint裡可以拖出相關節點
-
- Hearing Range 聽覺距離
- Detection by Affiliation 決定誰能觸發事件（敵人/路人/友軍）
- Affiliation目前只能在C++裡定義
- 在blueprint裡可以勾上Dectect Neutrals（路人）來檢測所有Actor
- Detection by Affiliation 決定誰能觸發事件（敵人/路人/友軍）
- Hearing Range 聽覺距離
Touch 接觸感知
- 應在被甚麼碰到/碰到甚麼時觸發
- 響應Report Touch Event
- blueprint裡可以拖出相關節點
Team Sense 隊友感知
- 同陣營接近的時候會通知
- 需要配合C++食用
AI Prediction Sense 預測感知
- 目的是為了讓AI發現玩家後，在跟蹤的過程中跟丟之後，依然會對玩家的可能移動結果進行一個以時間為單位的推算，並得出一個新的目標位置
- 需要配合其他Sense使用，如以下視野檢測：
- 當Stimulus Successfully Sensed為false時（看不見了），接入Request Pawn/Character Prediction Event節點，請求做一次Prediction Sense
- 然後會觸發Perception Update事件，再在該事件裡增加對Prediction Sense的處理
Damage Sense 傷害感知
- 響應 Report Damage Event / Apply Any Damage / Apply Radial Damage / Apply Point Damage
- blueprint裡可以拖出相關節點
共同參數
- Dominant Sense => 最優先感知，應該是已配置的感知其中之一
- StartsEnabled：該感知是否要手動啟動，true為不需要
- 手動啟動流程：調用SetSenseEnabled，指定具體的Sense Class
- MaxAge：感知持續時間，0代表永久持續
- 單位是秒
- Age會每幀按一定的增長率遞增，一旦 Age >= MaxAge（ExpirationAge），感知就會「過期」
- 增長率可以在UAIPerceptionSystem的初始化列表裡修改
//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;
}