获取鼠标在世界中的位置

-获取鼠标位置有很多方法，这里说三种，但只是提供方法，具体并不是很清楚

一、GetHitResultUnderCursorByChannel

FHitResult TraceHitResult;//检测结果
GetHitResultUnderCursorByChannel(TraceTypeQuery1, true, TraceHitResult);    
FVector pos = TraceHitResult.Location;//位置

看一下源码

bool APlayerController::GetHitResultUnderCursorByChannel(ETraceTypeQuery TraceChannel, bool bTraceComplex, FHitResult& HitResult) const
{
    ULocalPlayer* LocalPlayer = Cast(Player);
    bool bHit = false;
    if (LocalPlayer && LocalPlayer->ViewportClient)
    {
        FVector2D MousePosition;
        if (LocalPlayer->ViewportClient->GetMousePosition(MousePosition))
        {
            bHit = GetHitResultAtScreenPosition(MousePosition, TraceChannel, bTraceComplex, HitResult);
        }
    }

    if(!bHit)   //If there was no hit we reset the results. This is redundant but helps Blueprint users
    {
        HitResult = FHitResult();
    }

    return bHit;
}

我推测是根据追踪类型进行定位，不是很清楚

二、GetHitResultUnderCursor

FHitResult bTraceHitResult;
GetHitResultUnderCursor(ECC_Visibility, true, bTraceHitResult);
FVector pos = bTraceHitResult.Location;//位置

看一下源码

bool APlayerController::GetHitResultUnderCursor(ECollisionChannel TraceChannel, bool bTraceComplex, FHitResult& HitResult) const
{
    ULocalPlayer* LocalPlayer = Cast(Player);
    bool bHit = false;
    if (LocalPlayer && LocalPlayer->ViewportClient)
    {
        FVector2D MousePosition;
        if (LocalPlayer->ViewportClient->GetMousePosition(MousePosition))
        {
            bHit = GetHitResultAtScreenPosition(MousePosition, TraceChannel, bTraceComplex, HitResult);
        }
    }

    if(!bHit)   //If there was no hit we reset the results. This is redundant but helps Blueprint users
    {
        HitResult = FHitResult();
    }

    return bHit;
}

和第一种很像，只有一个参数是变化的，推测是根据碰撞类型进行定位，因为在碰撞设置的时候也会设置对于Trace的反应。

三、LineTraceSingleByChannel，之前说过LineTraceSingleForObjects，这里是ByChannel

        FHitResult HitResult,Start, Dir, End, ;
        DeprojectMousePositionToWorld(Start, Dir);//获取初始位置和方向
        End = Start + (Dir*8000.0f);//设置追踪终点
        GetWorld()->LineTraceSingleByChannel(HitResult, Start, End, ECC_Visibility);
        FVector pos = HitResult.Location;//位置

只看一下DeprojectMousePositionToWorld的源码吧

bool APlayerController::DeprojectMousePositionToWorld(FVector& WorldLocation, FVector& WorldDirection) const
{
    ULocalPlayer* const LocalPlayer = GetLocalPlayer();
    if (LocalPlayer && LocalPlayer->ViewportClient)
    {
        FVector2D ScreenPosition;
        if (LocalPlayer->ViewportClient->GetMousePosition(ScreenPosition))
        {
            return UGameplayStatics::DeprojectScreenToWorld(this, ScreenPosition, WorldLocation, WorldDirection);
        }
    }

    return false;
}


//被调用的方法
bool UGameplayStatics::DeprojectScreenToWorld(APlayerController const* Player, const FVector2D& ScreenPosition, FVector& WorldPosition, FVector& WorldDirection)
{
    ULocalPlayer* const LP = Player ? Player->GetLocalPlayer() : nullptr;
    if (LP && LP->ViewportClient)
    {
        // get the projection data
        FSceneViewProjectionData ProjectionData;
        if (LP->GetProjectionData(LP->ViewportClient->Viewport, eSSP_FULL, /*out*/ ProjectionData))
        {
            FMatrix const InvViewProjMatrix = ProjectionData.ComputeViewProjectionMatrix().InverseFast();
            FSceneView::DeprojectScreenToWorld(ScreenPosition, ProjectionData.GetConstrainedViewRect(), InvViewProjMatrix, /*out*/ WorldPosition, /*out*/ WorldDirection);
            return true;
        }
    }

    // something went wrong, zero things and return false
    WorldPosition = FVector::ZeroVector;
    WorldDirection = FVector::ZeroVector;
    return false;
}