Socket checks?
It’s a bit strange though, the engine clearly does ‘something’ when an object is completely out of frame or completely obscured, the engine can clearly tell when the player is not able to see an object, it’s strange that blueprints can’t check for this ‘something’.
You can for instance see it with planar reflections, they stop eating up your frames when they can’t be seen by the player. You can also see it with niagara systems, they stop the second you’re not looking at their origin, or if an object obstructs your view of it.