Smart Enemy AI

• 课程链接

• 项目地址

Behavior Tree

Basic Enemy Behavior

AIMoveTo节点在C++中的实现：

UAIAsyncTaskBlueprintProxy* UAIBlueprintHelperLibrary::CreateMoveToProxyObject(...)

在场景中添加导航网格，然后按P显示：

上面的逻辑替换为BehaviorTree：

黑板设置：

在AIController中初始化行为树，设置黑板数值。

void ABaseAIController::InitDefaultBT()
{
	RunBehaviorTree(DefaultBT);
	ACharacter* TargetPlayer = UGameplayStatics::GetPlayerCharacter(this, 0);
    // 使用字符串对黑板中的对象进行绑定
	Blackboard->SetValueAsObject("AttackTarget", TargetPlayer);
}

Custom Task Node

EBTNodeResult::Type UBTTask_DefaultAttack::ExecuteTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory)
{
	AAIController* const MyController = OwnerComp.GetAIOwner();
	EBTNodeResult::Type Result = EBTNodeResult::Failed;
	if (MyController->GetPawn()->Implements<UEnemyInterface>())
	{
		IEnemyInterface::Execute_Attack(MyController->GetPawn());
		Result = EBTNodeResult::Succeeded;
	}
	return Result;
}

添加 自定义节点自己控制结束

常实现方法：

• 激活：virtual EBTNodeResult::Type ExecuteTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) override;
• 退出：virtual EBTNodeResult::Type AbortTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) override;
• 轮询：virtual void TickTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory, float DeltaSeconds) override;

Blackboard Selector

头文件：

UCLASS()
class SMARTENEMYAI_API UBTTask_FocusTarget : public UBTTaskNode
{
	GENERATED_BODY()

public:
	UBTTask_FocusTarget(const FObjectInitializer& ObjectInitialize);

protected:
	virtual EBTNodeResult::Type ExecuteTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) override;

	virtual void InitializeFromAsset(UBehaviorTree& Asset) override;

protected:
	/** blackboard key selector */
	UPROPERTY(EditAnywhere, Category = Blackboard)
	struct FBlackboardKeySelector AttackTargetKey;
};

实现：

#include "AI/Task/BTTask_FocusTarget.h"

#include "AIController.h"
#include "BehaviorTree/BlackboardComponent.h"

UBTTask_FocusTarget::UBTTask_FocusTarget(const FObjectInitializer& ObjectInitialize)
{
	NodeName = "Focus Target";
	// 设置过滤
	AttackTargetKey.AddObjectFilter(this, GET_MEMBER_NAME_CHECKED(UBTTask_FocusTarget, AttackTargetKey), AActor::StaticClass());
}

EBTNodeResult::Type UBTTask_FocusTarget::ExecuteTask(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory)
{
	EBTNodeResult::Type Result = EBTNodeResult::Failed;

	AAIController* const MyController = OwnerComp.GetAIOwner();
	UBlackboardComponent* Blackboard = OwnerComp.GetBlackboardComponent();
	if (!MyController || !Blackboard || !AttackTargetKey.IsSet())
	{
		return Result;
	}

	if (AActor* Target = Cast<AActor>(Blackboard->GetValueAsObject(AttackTargetKey.SelectedKeyName)))
	{
		MyController->SetFocus(Target);
		Result = EBTNodeResult::Succeeded;
	}

	return Result;
}

void UBTTask_FocusTarget::InitializeFromAsset(UBehaviorTree& Asset)
{
	Super::InitializeFromAsset(Asset);

	// 从资产中解析选中的键名
	if (const UBlackboardData* BBAsset = GetBlackboardAsset())
	{
		AttackTargetKey.ResolveSelectedKey(*BBAsset);
	}
	else
	{
		AttackTargetKey.InvalidateResolvedKey();
	}
}

Set Focus

在使用AAIController::SetFocus后，想要角色跟着旋转需要在角色上开启以下选项：

Custom Decorator

提前判断任务是否可以执行的节点

主要实现方法：

• virtual bool CalculateRawConditionValue(UBehaviorTreeComponent& OwnerComp, uint8* NodeMemory) const override;

最终的行为树：