[UE4]C++创建BoxCollision(BoxComponent)并注册Overlap和Hit事件回调函数

keywords: UE4, Overlap, Hit, Event, Callback, C++, Box Collision, BoxComponent、SphereComponent, Trace Channel, 碰撞

蓝图方式：
[UE4]Box Collision的Overlap事件注册和触发(蓝图方式)

BoxComponent的Overlap事件

1，C++中的代码编写

这里我们演示的例子，是在角色身上创建一个BoxComponent，假设角色的C++ class叫AMyCharacter。 MyCharacter.h头文件中定义：

//Box对象
UBoxComponent* CollisionMesh;

//OverlapBegin事件的回调函数，注意函数签名！
UFUNCTION()
    void OnTestOverlapBegin(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult);

//OverlapEnd事件的回调函数，注意函数签名！
UFUNCTION()
    void OnTestOverlapEnd(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex);

旧版本函数签名：

UFUNCTION()
    void OnTestOverlapBegin(class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult);
    
UFUNCTION()
    void OnTestOverlapEnd(class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex);

MyCharacter.cpp的构造函数中：

//创建BoxComponent
CollisionMesh = CreateDefaultSubobject<UBoxComponent>(TEXT("TestCollision"));
CollisionMesh->SetBoxExtent(FVector(200.f, 200.f, 96.f));
CollisionMesh->bDynamicObstacle = true;
CollisionMesh->SetupAttachment(GetRootComponent());
//如果需要Overlap事件，将bGenerateOverlapEvents设置为true。如果不设置，默认也为true。
CollisionMesh->bGenerateOverlapEvents = true;

//注意：要触发Overlap事件，SetCollisionResponseToAllChannels要么不设置，要么设置为ECR_Overlap。
CollisionMesh->SetCollisionResponseToAllChannels(ECR_Overlap);
/*CollisionMesh->SetCollisionResponseToChannel(ECC_WorldStatic, ECR_Block);
CollisionMesh->SetCollisionResponseToChannel(ECC_WorldDynamic, ECR_Block);
CollisionMesh->SetCollisionResponseToChannel(ECC_Pawn, ECR_Block);
CollisionMesh->SetNotifyRigidBodyCollision(true);
CollisionMesh->SetSimulatePhysics(true);*/

//要触发Overlap事件，碰撞对象需要勾选属性：Generate Overlap Events
FScriptDelegate DelegateBegin;
DelegateBegin.BindUFunction(this, "OnTestOverlapBegin");
CollisionMesh->OnComponentBeginOverlap.Add(DelegateBegin);
FScriptDelegate DelegateEnd;
DelegateEnd.BindUFunction(this, "OnTestOverlapEnd");
CollisionMesh->OnComponentEndOverlap.Add(DelegateEnd);

回调函数的函数体：

void AMyCharacter::OnTestOverlapBegin(class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult)
{
    GEngine->AddOnScreenDebugMessage(-1, 2.f, FColor::Red, FString("Begin++++++++++++ ") + SweepResult.Location.ToString());
}

void AMyCharacter::OnTestOverlapEnd(class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex)
{
    GEngine->AddOnScreenDebugMessage(-1, 2.f, FColor::Red, FString("End--------------- ") + OtherActor->GetName());
}

2，场景中的对象属性设置

想触发Overlap事件时，场景中的碰撞对象需要勾选的选项：Generate Overlap Events

这样，当角色走到场景对象的附近，且身上的box与该物体发生碰撞时，就可以触发Overlap事件。

BoxComponent的Hit事件

1，C++中的代码编写

MyCharacter.h头文件中定义：

//Box对象
UBoxComponent* CollisionMesh;

//Hit事件的回调函数，注意函数签名！
UFUNCTION()
        void OnTestHit(UPrimitiveComponent* HitComponent, AActor* OtherActor, UPrimitiveComponent* OtherComponent, FVector NormalImpulse, const FHitResult& Hit);

MyCharacter.cpp的构造函数中：

//创建BoxComponent
CollisionMesh = CreateDefaultSubobject<UBoxComponent>(TEXT("TestCollision"));
CollisionMesh->SetBoxExtent(FVector(200.f, 200.f, 96.f));
CollisionMesh->bDynamicObstacle = true;
CollisionMesh->SetupAttachment(GetRootComponent());
//注意：如果要让CollisionMesh->OnComponentHit的回调事件触发，必须设置：CollisionMesh->BodyInstance.SetCollisionProfileName
CollisionMesh->BodyInstance.SetCollisionProfileName("MyCollisionProfile");
CollisionMesh->SetNotifyRigidBodyCollision(true);

//要触发Hit事件，碰对对象需要勾选属性：Simulation Generates Hit Events
FScriptDelegate DelegateHit;
DelegateHit.BindUFunction(this, "OnTestHit");
CollisionMesh->OnComponentHit.Add(DelegateHit);

注意，上面设置的ProfileName：MyCollisionProfile，是在Project Settings中设置的，具体步骤见Collision Channel 设置。

回调函数的函数体：

void AMyCharacter::OnTestHit(UPrimitiveComponent* HitComponent, AActor* OtherActor, UPrimitiveComponent* OtherComponent, FVector NormalImpulse, const FHitResult& Hit)
{
    GEngine->AddOnScreenDebugMessage(-1, 2.f, FColor::Red, FString("Hit&&&&&&&&&&&&&&&& ") + Hit.Location.ToString());
}

2，场景中的碰撞对象需要设置的选项

• Simulate Physics：如果要触发Hit事件，这个属性必须勾选。对应的C++函数：UPrimitiveComponent::SetSimulatePhysics(bool bSimulate)。
• Simulation Generates Hit Events：表示是否触发当前物体的Hit事件，如果你需要的回调事件不是这个物体的，可以不勾选该选项。对应的C++属性叫做FBodyInstance::bNotifyRigidBodyCollision，C++函数叫：UPrimitiveComponent::SetNotifyRigidBodyCollision(bool bNewNotifyRigidBodyCollision)。
• Collision Presets：同上，如果不关心当前物体的碰撞规则，只是希望其他物体碰到当前物体时，能触发其他物体的碰撞事件，那么Collision Presets可以设置为默认值。

Collision Channel 设置

编辑器中设置 Collision Proifle

打开工程设置：Edit -》 Project Settings -》 Engine -》 Collision

然后点击Object Channel下的New Object Channel：

写一个名字，并将Response设置为Block。

然后点击Accept，这样Object Channels就多了一条记录

然后点击Preset下的New：

• Name自己定义，这里的Name就是之前C++代码中设置ProfileName中的名字MyCollisionProfile；
• CollisionEnabled设置为Collision Enabled；
• ObjectType设置为上面步骤添加的记录；
• Collision Response: 因为示例需要的是Hit事件，不是Overlap，所以Collision Response设置为Block；

其中 CollisionEnabled 类型如下：

• No Collision 全部禁用，物体会坠入地表，且没有物理；
• Query Only 只启用碰撞，不会坠入地表，但是没有物理；
• Physics Only 只启用物理，但是会坠入地表；
• Collision Enabled 同事启用碰撞和物理，既不会坠入地表，同时有物理；

点击Accept之后，就在Preset列表中多了一条记录

Collision Object Channel、Collision Preset、Object Type 三者联系：

• Project Settings 中的 Object Channel 对应蓝图中 CollisionComponent 或者 MeshComponent 中的属性 Object Type 和 Object Response；
• Project Settings 中的 Collision Preset 对应蓝图中 CollisionComponent 或者 MeshComponent 中的属性 Collision Presets；

如果蓝图中 CollisionComponent 或者 MeshComponent 中的属性 Collision Presets 选择预设好的 Preset ，则 Object Type 等其他 Collision 相关属性不可编辑。

如果选择 Collision Presets 选择 Custom ，则可以相关属性可以编辑。相关参数含义是：

• Object Type 表示当前物体所属的 Collision Channel ，即：Collision Presets拥有者对 Object Type 物体的影响，前者 忽略、重叠或者阻挡后者；
• Object Response 表示当前物体与其他物体所对其他 Collision Channel 物体的反应：Ingore(忽略)、Overlaop(重叠)还是Block(阻挡)。

实际应用：
假如有三个物体A、B、C，A物体身上有个 CollisionBox，希望这个 CollisionBox 只与物体B发生 Overlap，忽略掉物体C（既不 Overlap 也不 Block ）。
方式如下：
新建两个 Collision Channel，分别作为物体B和物体C的 Object Type；然后再新建一个 Collision Preset，假设叫 CollisionProfileA ，并设置该 Preset 对物体B的通道 Overlap ， 对物体C的通道 Ingore ，然后将物体A的 Collision Preset 设置成 CollisionProfileA。

C++ 设置 Collision

//设置自定义 Collision 配置（只能在构造函数中使用）
GetCollisionComponent()->SetCollisionProfileName("Custom");

//设置指定通道的Response
GetCollisionComponent()->SetCollisionResponseToChannel(ECC_Pawn, ECollisionResponse::ECR_Ignore);

//为自己设置自定义 Collision 通道
GetCollisionComponent()->BodyInstance.SetObjectType(ECollisionChannel::ECC_GameTraceChannel1);

其中 ECollisionChannel::ECC_GameTraceChannel1 为 Object Channels，例如：TestCollChannel。

TestCollChannel对应哪一个 ECollisionChannel，可以在DefaultEngine.ini找到，例如：
+DefaultChannelResponses=(Channel=ECC_GameTraceChannel1,Name="TestCollChannel",DefaultResponse=ECR_Block,bTraceType=False,bStaticObject=False)

SetCollisionProfileName 注意事项

如果在非构造函数中执行SetCollisionProfileName会导致什么样的问题？
在非构造函数中修改 CollisionProfile ，可以修改当前物体的Collision Channel，即：当前物体对其他 Object Type物体是 Ignore、Overlap 还是 Block。 但是无法修改当前物体的 CollisionEnabled ，即：是否启用物理、是否启用碰撞等设置无法生效。

Actor的Hit事件（两种方式）

方式1：OnActorHit 代理

1. C++代码的编写：
   Actor的Hit事件不需要BoxComponent，只需要注册回调即可，回调函数的签名与上面例子的函数签名一样。

    FScriptDelegate DelegateHit;
    DelegateHit.BindUFunction(this, "OnTestHit");
    this->OnActorHit.Add(DelegateHit);
   

2. 场景中的碰撞对象需要设置的选项：
   只要默认即可，不需要设置属性。

注意事项

如果是用BoxComponent去碰撞其他物体，且想触发BoxComponent的Hit事件（通过BoxComponent.OnComponentHit.Add()注册），那么其他物体的Simulate Physics属性必须设置为true，且Collision Presets属性不要设置为NoCollision； 如果是用Actor去碰撞其他物体，且想触发Actor的Hit事件（通过Actor.OnActorHit.Add()注册），那么其他物体的Simulate Physics属性设置为true或false均可，且Collision Presets属性不要设置为NoCollision。

方式2：重写 NotifyHit 函数

/** 
 * Event when this actor bumps into a blocking object, or blocks another actor that bumps into it.
 * This could happen due to things like Character movement, using Set Location with 'sweep' enabled, or physics simulation.
 * For events when objects overlap (e.g. walking into a trigger) see the 'Overlap' event.
 *
 * @note For collisions during physics simulation to generate hit events, 'Simulation Generates Hit Events' must be enabled.
 * @note When receiving a hit from another object's movement (bSelfMoved is false), the directions of 'Hit.Normal' and 'Hit.ImpactNormal'
 * will be adjusted to indicate force from the other object against this object.
 */
virtual void AActor::NotifyHit(class UPrimitiveComponent* MyComp, AActor* Other, class UPrimitiveComponent* OtherComp, bool bSelfMoved, FVector HitLocation, FVector HitNormal, FVector NormalImpulse, const FHitResult& Hit);

Actor的Overlap事件（两种方式）

方式1：OnActorBeginOverlap 注册回调

1. 注册回调

    void AMyCharacter::BeginPlay()
    {
        Super::BeginPlay();
   
        FScriptDelegate Del;
        Del.BindUFunction(this, TEXT("OnOverlap"));
        OnActorBeginOverlap.Add(Del);
    }
   

2. 编写回调函数

   header

    UFUNCTION()
    void OnOverlap(AActor* OverlappedActor, AActor* OtherActor);
   

   cpp

    void ATestTD2Character::OnOverlap(AActor* OverlappedActor, AActor* OtherActor)
    {
        GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Red, FString::Printf(TEXT("%s  %s  %s"), *GetName(), *OverlappedActor->GetName(), *OtherActor->GetName()));
    }
   

方式2：重写 NotifyActorBeginOverlap 函数

/** 
 *    Event when this actor overlaps another actor, for example a player walking into a trigger.
 *    For events when objects have a blocking collision, for example a player hitting a wall, see 'Hit' events.
 *    @note Components on both this and the other Actor must have bGenerateOverlapEvents set to true to generate overlap events.
 */
virtual void AActor::NotifyActorBeginOverlap(AActor* OtherActor);

Overlap事件开关

void UPrimitiveComponent::SetGenerateOverlapEvents(bool bInGenerateOverlapEvents)

其他与碰撞相关

Component自身提供的检测函数

UPrimitiveComponent::LineTraceComponent();
UPrimitiveComponent::SweepComponent();
UPrimitiveComponent::ComponentOverlapComponent();
UPrimitiveComponent::OverlapComponent(); 

C++ AActor::OnActorBeginOverlap 对应的蓝图节点为：

EventActorBeginOverlap

C++ AActor::NotifyHit() 对应的蓝图节点为：

EventHit

Using pure C++ process Overlap Event of SkeletalMeshComponent

Header：

protected:

UFUNCTION()
    void OnOverlapBegin(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult);

UFUNCTION()
    void OnOverlapEnd(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex);

Constructor

GunMesh = CreateDefaultSubobject<USkeletalMeshComponent>(TEXT("GunMesh"));
GunMesh->SetupAttachment(RootComponent);
static ConstructorHelpers::FObjectFinder<USkeletalMesh> GunAsset(TEXT("SkeletalMesh'/Game/Assets/Weapons/Meshes/AR4/SK_AR4.SK_AR4'"));
if (GunAsset.Succeeded())
{
    GunMesh->SetSkeletalMesh(GunAsset.Object);
}
GunMesh->SetRelativeLocation(FVector(200.f, 0.f, 100.f));
GunMesh->SetGenerateOverlapEvents(true);
GunMesh->SetCollisionProfileName("OverlapAll");

Register Event：

void ATestTD2Character::BeginPlay()
{
    Super::BeginPlay();

    GunMeshComp->OnComponentBeginOverlap.AddDynamic(this, &ATestTD2Character::OnOverlapBegin);

    GunMeshComp->OnComponentEndOverlap.AddDynamic(this, &ATestTD2Character::OnOverlapEnd);
}


void ATestTD2Character::OnOverlapBegin(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult & SweepResult)
{
    GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Yellow, FString("Weapon Overlap Begin ++++++"));
}

void ATestTD2Character::OnOverlapEnd(UPrimitiveComponent* OverlappedComponent, AActor* OtherActor, UPrimitiveComponent* OtherComp, int32 OtherBodyIndex)
{
    GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Yellow, FString("Weapon Overlap End ------"));
}

更多参考：
Events
https://docs.unrealengine.com/latest/INT/Engine/Blueprints/UserGuide/Events/index.html#eventhit

Collision Filtering
https://www.unrealengine.com/en-US/blog/collision-filtering

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