Light Switch Overlap Trigger

December 02, 2017

UE4 Version: 4.18.3

Github Link: https://github.com/Harrison1/unrealcpp/tree/master/LightSwitchTrigger

For this tutorial we are using the standard first person C++ template with starter content. If you don't know how to add a new actor class to your project, please visit the Add C++ Actor Class post.

The main logic of this code is from Epic's Unreal Engine 4 documentation and you can see it here.

In this tutorial we are going to make a light that turns on and off when a user enters the actor's USphereComponent. Create a new C++ actor class and call it LightSwitchTrigger. In the header we will define our PointLight, USphereComponent, Overlap functions, and ToggleLight function.

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();
};

Next, in the .cpp we will #include DrawDebuHelpers to help us visualize the collision sphere.

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

In the LightSwitchTrigger init function we will set our LightIntensity to 3000.0f. Next, we'll add a PointLight as our RootComponent. Then we'll add a USphereComponent to our actor for a trigger sphere and attach it to the RootComponent. Then connect USphereComponent to our Overlap functions that we will create later.

setup up trigger light

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); 

}

In the BeginPlay() add a debug sphere with sama radius as our LightSphere.

draw debug sphere

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

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

Create a function called ToggleLight() that toggles the PointLight's visibility. Visit this page in the documentation to view all of the USceneComponent's functions and properties.

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

Next, we'll create two overlap functions that both call the ToggleLight function to toggle the visibility of the light.

overlap functions

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();
    }
}

Finally, compile the code and drag the LightSwitchTrigger into the scene. Now whenever the player enters the sphere comp the light will toggle. Below is the final .cpp file.

LightSwitchTrigger.cpp

#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();
}

Author

Harrison McGuire

Harrison McGuire