射线检测：

FVector Start; //射线起点

FRotator ViewRotator;

GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(Start, ViewRotator);

FVector End = Start + ViewRotator.Vector() * 100(cm);

DrawDebugLine(GetWorld(), start, end, FColor(255,0,0), false, 0,  0, 10);//画辅助线 

添加抓取功能：

在DefaultPawn_Blueprint文件中：

添加组件---新建C++组件...

第二步，选择Actor Component ：

第三步，名称改称为Grabber，抓取器：

创建类

Unreal Engine 4 中的坐标/向量 FVector

FVector Start;

获取PlayerController()

#include "Engine/World.h"

GetWorld()->GetFirstPlayerController()

PlayerController : 控制Player的移动的

使用DrawDebugLine

需要引用 #include "DrawDebugHelpers.h"

DrawDebugLine(GetWorld(), Start, End, FColor(255, 0, 0), false, 0, 0, 10);

API

void DrawDebugLine()
{
    const UWorld * InWorld,
    FVector const & LineStart,
    FVector const & LineEnd,
    FColor const & Color,
    bool bPersistentLines;
    float LifeTime,
    uint8 DepthPriority,
    float Thickness
}

编译没看到线，先保存一下蓝图类DefaultPawn_Blueprint ！！！

#include "Grabber.h"
#include "Engine/World.h"
#include "DrawDebugHelpers.h"


UGrabber::UGrabber()
{
	PrimaryComponentTick.bCanEverTick = true;
}


void UGrabber::BeginPlay()
{
	Super::BeginPlay();	
}


void UGrabber::TickComponent(float DeltaTime, ELevelTick TickType, FActorComponentTickFunction* ThisTickFunction)
{
	Super::TickComponent(DeltaTime, TickType, ThisTickFunction);

	FVector Start;
	FRotator ViewRotator;
	GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(Start, ViewRotator);

	FVector End = Start + ViewRotator.Vector()*100; // ViewRotator.Vector() 视野的正中心 前方 100cm

	DrawDebugLine(GetWorld(), Start, End, FColor(255, 0, 0), false, 0, 0, 10);
}