In this time, to get StartLocation(2nd arg of LineTraceSingleByChannel function), Ben used
PlayerCameraManager->GetCameraLocation();
but I used
FVector PlayerViewpointLocation; // Out Param
FRotator PlayerViewPointRotation; // No use
GetPlayerViewPoint(PlayerViewpointLocation, PlayerViewPointRotation);
FVector StartLocation = PlayerViewpointLocation;
So I looked up Engine Source(Runtime/Engine/Private/PlayerController.cpp)
And I found that maybe it is same depends on conditions(?)
Is it correct?? 