最简单的 UE 4 C++ 教程 —— 触发区域的灯光切换【二十三】

原教程是基于 UE 4.18，我是基于 UE 4.25

英文原地址

核心 API

OnComponentBeginOverlap.AddDynamic()

OnComponentEndOverlap.AddDynamic()

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《最简单的 UE 4 C++ 教程 —— 为 Charactor 添加重叠事件【十九】》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 DrawDebuHelpers.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

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); 

}

 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。

​

放置触发区域到场景中

游戏运行的效果图：进入触发区域关闭灯光，离开触发区域开启灯光

​

进进出出触发区域以切换灯光的开启状态