We all know that the ray in UE is very important. We will use blueprint to add components
But I will not use C + + to add. Today, I will teach you how to use C + + code to realize it
IDE:VS2017
UE version: 4.17

First rendering:

We create a C + + project to give empty
After startup, press F8 to select the default pawn and add a blueprint script
We call it "DB" pawn

Add a C + + component, the system will automatically open our VS

The first step is to write the following code in. h

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once
#include "CoreMinimal.h"
#include "Components/ActorComponent.h"
#include "Engine/World.h"
#include "Public/DrawDebugHelpers.h"
#include "DrawDebugLine_Cpp.generated.h"

UCLASS( ClassGroup=(Custom), meta=(BlueprintSpawnableComponent) )
class DRAWDEBUGLINE_API UDrawDebugLine_Cpp : public UActorComponent
{
    GENERATED_BODY()

public: 
    // Sets default values for this component's properties
    UDrawDebugLine_Cpp();

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

public: 
    // Called every frame
    virtual void TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction) override;

    FVector PlayerLocation; //Ray starting point
    FRotator PlayerRotator;//Face to face

    float lang = 100000.0f;     //Length of ray
    
};

Write the following code from cpp

// Fill out your copyright notice in the Description page of Project Settings.

#include "DrawDebugLine_Cpp.h"


// Sets default values for this component's properties
UDrawDebugLine_Cpp::UDrawDebugLine_Cpp()
{
    // Set this component to be initialized when the game starts, and to be ticked every frame.  You can turn these features
    // off to improve performance if you don't need them.
    PrimaryComponentTick.bCanEverTick = true;

    // ...
}


// Called when the game starts
void UDrawDebugLine_Cpp::BeginPlay()
{
    Super::BeginPlay();

    // ...
    
}


// Called every frame
void UDrawDebugLine_Cpp::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction)
{
    Super::TickComponent(DeltaTime, TickType, ThisTickFunction);

    GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(PlayerLocation, PlayerRotator);//Define the start and direction of the ray

    FVector LineEnd = PlayerLocation + PlayerRotator.Vector()*lang;//Define the end point of the ray
    //Call the draw ray function
    DrawDebugLine(
        GetWorld(),
    PlayerLocation,
    LineEnd,
    FColor::Blue,
    false,
    0.0f,
    0.0f,
    10.0f
    );

}

Then go back to the editor and set the written DB [pawn] to the default PawnClass. If it can't be set, create a new game mode,

Compile and play

If you can't see it, move left and right