So, I'm finally getting to the point where I need to start thinking about optimizing the levels I've been building. However, I'm not sure which is a better way to go about doing this.

Now, I know the main option would be roombounds, however they can be very tricky and time consuming to set up, so I'd love it if I can avoid that.

So my question is, is there a downside to using occlusion planes to cut up a level instead? I can place them between large rooms (outside of the rooms in the deadspace, obviously) so that the other areas aren't rendered. However, this almost seems to me like it would be very processor heavy, if with every step it's recalculating what the engine should and shouldn't cull. Is this assumption correct? Or am I assuming incorrectly? Will placing, like, 3-10 occlusion planes around a level between large areas actually reduce performance, or is that calculation very minor, and will the saved rendering more than make up for it?

Yes, that method you describe would be more intensive and backward than just using two Roombounds and a Portal. I'm not sure by how much, but it would be, and I would not really recommend doing that. It's the difference between one OC object being added to the scene graph per room versus five or ten. You can have too much of a good thing. Add up how many per-room that is, and you would not be doing anyone's CPU any favors with all the Culls that need to be processed every frame (one versus ten, again, they add up). I don't like to advocate cheap tricks to get around something that can be done but you don't want to because "it's too hard." That to me speaks lazy work.

The rule of thumb: Roombounds for interiors, Occlusion Planes for exteriors. Roombounds actually aren't that much of a PITA, they just take some getting used to.

Eh, not so much lazy work for me, more of a 'I have to make like 3 dungeons a week and would like to save time wherever I reasonably can'

So it sounds like I'll have to learn roombounds. I'll just try to do like 3 roombounds a level so it breaks up into large chunks, that should cut away any staggering performance issues.

Thanks for the input.

You don't have to be pedantic with them, just divide your dungeons up into what you feel are reasonable chunks with them and stick portals wherever two roombounds meet and you want the player to see through them.

Not hard at all. It's pretty much the same methodology as placing occlusion planes, only with the addition of portals, and those are easy to learn.