@Zombie13: Have you worked with idTech 5? I wonder how it is compare to idTech 4 and UE3/4 when it comes to visibility culling (manual vs automatic vs semi-automatic).
So, this was an interest to me, so I took a look to see how it works.
It would seem that a similar visibility culling system, functionally speaking, to that found in UE3, where you don't explicitly define visportals, but rely on occlusion and player view to select what to render. There is no visportal texture in the common or editor folders, and I assume that is because the Id tech 5 renderer does not need/use them.
Probably, many of you will already have known that vis would be handled differently then in previous engines by Id, but for the sake of completeness, i hope that helps a bit.
There is however, a player vis clip, which would indicate that the occlusion can be more rigidly defined by brushes, possible with the hallway method we are all so familiar with, but without visportal brushes.
In closing, Id Tech 5 renderer culling: sorta like UE3 (UE4 too maybe, idk?), but definitely geared toward open areas with models etc. which was kind of evident from the pop in we also see in UE3 possibly due to similar player view/occluders/update renderer method of culling being used.
Clearly, I am no graphics programmer, so please chime in and correct me.