UE4-DrawDebugLine.cpp

#define OUT

// Used for saving ViewPortLocation
FVector PlayerViewPointLocation;
// Used for saving ViewPortRotation
FRotator PlayerViewPointRotation;

void GetPlayerViewPort(){
  GetWorld()->GetFirstPlayerController()->GetPlayerViewPoint(
    OUT PlayerViewPointLocation,
    OUT PlayerViewPointRotation );
}

FVector GetReachLineEnd(){
  GetPlayerViewPort();
  return PlayerViewPointLocation + (PlayerViewPointRotation.Vector() * Reach);
}

/// Drawing a red debug line
DrawDebugLine( GetWorld(), PlayerViewPointLocation, GetReachLineEnd(), FColor( 255, 0, 0 ), false, 0.f, 0, 2.f );