Determine actor visibility using camera rotation

I trying to draw enemy healthbar over his head.
At first I found bounding box that contains enemy:

FBox boundingBox = EnemyInfoArray[i].Actor->GetComponentsBoundingBox();

Then I project world coordinates to screen:

pos = Project(EnemyInfoArray[i].Actor->GetActorLocation());

And then use it like this:

posX = pos.X - mainWidth / 2 + border / 2;
posY = Project(boundingBox.Max).Y - mainHeight + border / 2;

DrawRect(FLinearColor::Red, posX, posY, healthWidth, mainHeight);

And the problem is that when I rotate my camera (FPS) 180 dergees healthbar still visible on screen. I trying use LineOfSightTo() and GetLastRenderTime() to determine visible actor or not but the both affected only by obstacles not by camera rotation.

How can I fix it?



Finally I check UCanvas::Project() and find that if object behind the screen then result Z-component will be 0. And it works.