UE4用代码画一条射线

我们都知道UE里面的射线很重要，我们都会用蓝图去添加组件
但是不会用C++去添加，今天就教大家如何用C++代码去实现
IDE:VS2017
UE版本：4.17

首先效果图：

我们创建要给空的C++项目
启动之后按下 F8 选中默认的pawn添加一个蓝图脚本
我们命名成“DB_Pawn”

添加一个C++组件，系统会自动打开我们的VS

第一步我们在.h中写入如下代码

// 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;	//射线起点
	FRotator PlayerRotator;//面朝的方向

	float lang = 100000.0f;		//射线的长度
	
};

在从cpp中写入如下代码

// 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);//定义射线的起点和方向

	FVector LineEnd = PlayerLocation + PlayerRotator.Vector()*lang;//定义射线的终点
	//调用画射线函数
	DrawDebugLine(
		GetWorld(),
	PlayerLocation,
	LineEnd,
	FColor::Blue,
	false,
	0.0f,
	0.0f,
	10.0f
	);

}

然后回到编辑器，把写好的DB_Pawn设置成默认的PawnClass，如果不能设置，就新创建一个游戏模式，

编译播放，即可

如果看不见，就左右移动移动