Is the performance gained from culling anywhere on the level of bsp maps? I’ve tried making some levels in probuilder but start getting some performance issues unless I do the level in chunks. Also, the texture workflow is... not great. At least compared to build 3D or Doom Builder (or Hammer and Worldcraft for that matter). I’m kind of wondering if making a level editor on my own would be worth while, but don’t know how to handle loading at all. Nor how to cut up an area, like a making a room with a hole/dip in the middle: how do I determine the points of the triangles? Squares are easy, rings are hard. I’m almost tempted to jump ship to Unreal, but the over all workflow for unity is WAY better
Does it struggle in Editor or build? I've tried both Probuilder and SabreCSG. Both sucked in terms of performance in editor. One package that didn't sucked was RealtimeCSG. (Although its being in frozen-fixes-only phase right now, as the dev doesn't want to compete with Unity's Probuilder) One thing I can say that is fast. Its lightning fast in editor. And I've tested it on 10 years old laptop. For the build its performance is the same as 3D models. So, it depends on the level complexity. Splitting models into submodels aren't that diffucult there, as its basically based on the brush selection. TL;DR: If you feel like trying something new - try RealtimeCSG.
Umbra is really bad at culling. Even completely solid meshes sometimes fails to occlude stuff on the other side. It feels like it would be better algoritms out there.
I wouldn't say out of not competing with ProBuilder though I wish Unity had actually just bought RealtimeCSG and made that part of the building tool packages in Unity and given it full support in improving it as CSG tools have there place in level design. Anyway the RealtimeCSG dev @LogicalError-Unity3D is working on another CSG tool called Chisel in collaboration with some other devs and enthusiasts into CSG modelling, one of them a SaberCSG mod developer... https://github.com/RadicalCSG/Chisel.Prototype It will be the best when it's out for I'm sure, but until then RealTimeCSG is the best for now or SaberCSG is also worth checking out as its free and you can see if CSG modelling is for you. I found I'd use CSG over Probuilder for level design and texturing... Probuilder I might aswel just use Maya etc though maybe it's improved since I last tried it..ofc I'm just a Unity should just remake Maya in Unity kinda guy