23. 触发区域的灯光切换

接上一节教程，本教程需要注意的是，需要确保第一人称的 Character 是纯净的，即没有《为 Charactor 添加重叠事件》添加的代码，否则触发灯光的开关可能会有冲突。

在本教程中，我们将创建一个灯，当用户进入 actor 的 USphereComponent 时，它会打开或关闭。创建一个新的 C++ 角色类并将其命名为 LightSwitchTrigger 。在头文件中，我们将定义我们的 PointLight、USphereComponent``、Overlap 函数和 ToggleLight 函数。

LightSwitchTrigger.h

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "LightSwitchTrigger.generated.h"

UCLASS()
class UNREALCPP_API ALightSwitchTrigger : public AActor
{
    GENERATED_BODY()

public: 
    // Sets default values for this actor's properties
    ALightSwitchTrigger();

protected:
    // Called when the game starts or when spawned
    virtual void BeginPlay() override;

public: 
    // Called every frame
    virtual void Tick(float DeltaTime) override;

    // declare point light comp
    UPROPERTY(VisibleAnywhere, Category = "Light Switch")
    class UPointLightComponent* PointLight;

    // declare sphere comp
    UPROPERTY(VisibleAnywhere, Category = "Light Switch")
    class USphereComponent* LightSphere;

    // declare light intensity variable
    UPROPERTY(VisibleAnywhere, Category = "Light Switch")
    float LightIntensity;

    // declare overlap begin function
    UFUNCTION()
    void OnOverlapBegin(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult);

    // declare overlap end function
    UFUNCTION()
    void OnOverlapEnd(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex);

    // declare ToggleLight function
    UFUNCTION()
    void ToggleLight();
};

接下来，在 .cpp 中，我们将 `

include "DrawDebugHelpers.h"` 来帮助我们可视化碰撞球体。

#include "LightSwitchTrigger.h"
#include "Components/PointLightComponent.h"
#include "Components/SphereComponent.h"
// include draw debu helpers header file
#include "DrawDebugHelpers.h"

在 LightSwitchTrigger 初始函数中，我们将把光照强度设置为 3000.0f。接下来，我们将添加一个 PointLight 作为我们的 RootComponent 。然后，我们将为触发器球体 的 actor 添加一个USphereComponent(LightSphere），并将其附加到 RootComponent 。然后将 USphereComponent 连接到我们稍后将创建的 Overlap 函数。

设置触发器中的灯光

```cpp ALightSwitchTrigger::ALightSwitchTrigger() { // Set this actor to call Tick() every frame. You can turn this off to improve performance if you don't need it. PrimaryActorTick.bCanEverTick = true;

LightIntensity = 3000.0f;

PointLight = CreateDefaultSubobject<UPointLightComponent>(TEXT("Point Light"));
PointLight->Intensity = LightIntensity;
//PointLight->bVisible = true; 过时
//PointLight->SetVisibleFlag(true);
PointLight->SetVisibility(true);
RootComponent = PointLight;

LightSphere = CreateDefaultSubobject<USphereComponent>(TEXT("Light Sphere Component"));
LightSphere->InitSphereRadius(300.0f);
LightSphere->SetCollisionProfileName(TEXT("Trigger"));
LightSphere->SetupAttachment(RootComponent);

LightSphere->OnComponentBeginOverlap.AddDynamic(this, &ALightSwitchTrigger::OnOverlapBegin);
LightSphere->OnComponentEndOverlap.AddDynamic(this, &ALightSwitchTrigger::OnOverlapEnd);

} ```

在 BeginPlay() 中添加一个与 LightSphere 半径相同的调试球体。 

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

    DrawDebugSphere(GetWorld(), GetActorLocation(), 300.f, 50, FColor::Green, true, -1, 0, 2);

}

创建一个名为 ToggleLight() 的函数，用于切换 PointLight 的可见性。

void ALightSwitchTrigger::ToggleLight()
{
    PointLight->ToggleVisibility();
}

接下来，我们将创建两个重叠函数，它们都调用 ToggleLight 函数来切换灯光的可见性。

void ALightSwitchTrigger::OnOverlapBegin(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)
{
    if (OtherActor && (OtherActor != this) && OtherComp)
    {
        ToggleLight();
    }
}

void ALightSwitchTrigger::OnOverlapEnd(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex)
{
    if (OtherActor && (OtherActor != this) && OtherComp)
    {
        ToggleLight();
    }
}

完整的 cpp 代码如下 

#include "LightSwitchTrigger.h"
#include "Components/PointLightComponent.h"
#include "Components/SphereComponent.h"
// include draw debu helpers header file
#include "DrawDebugHelpers.h"

// Sets default values
ALightSwitchTrigger::ALightSwitchTrigger()
{
    // Set this actor to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
    PrimaryActorTick.bCanEverTick = true;

    LightIntensity = 3000.0f;

    PointLight = CreateDefaultSubobject<UPointLightComponent>(TEXT("Point Light"));
    PointLight->Intensity = LightIntensity;
    PointLight->bVisible = true;
    RootComponent = PointLight;

    LightSphere = CreateDefaultSubobject<USphereComponent>(TEXT("Light Sphere Component"));
    LightSphere->InitSphereRadius(300.0f);
    LightSphere->SetCollisionProfileName(TEXT("Trigger"));
    LightSphere->SetupAttachment(RootComponent);

    LightSphere->OnComponentBeginOverlap.AddDynamic(this, &ALightSwitchTrigger::OnOverlapBegin);
    LightSphere->OnComponentEndOverlap.AddDynamic(this, &ALightSwitchTrigger::OnOverlapEnd); 

}

// Called when the game starts or when spawned
void ALightSwitchTrigger::BeginPlay()
{
    Super::BeginPlay();

    DrawDebugSphere(GetWorld(), GetActorLocation(), 300.f, 50, FColor::Green, true, -1, 0, 2);

}

// Called every frame
void ALightSwitchTrigger::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

}

void ALightSwitchTrigger::OnOverlapBegin(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex, bool bFromSweep, const FHitResult& SweepResult)
{
    if (OtherActor && (OtherActor != this) && OtherComp)
    {
        ToggleLight();
    }
}

void ALightSwitchTrigger::OnOverlapEnd(class UPrimitiveComponent* OverlappedComp, class AActor* OtherActor, class UPrimitiveComponent* OtherComp, int32 OtherBodyIndex)
{
    if (OtherActor && (OtherActor != this) && OtherComp)
    {
        ToggleLight();
    }
}

void ALightSwitchTrigger::ToggleLight()
{
    PointLight->ToggleVisibility();
}

最后，编译代码并将 LightSwitchTrigger 拖到场景中。现在当玩家进入球体区域时，灯光就会切换开启状态。

参考