Static Mesh Actors: How Big Is Too Big?!!

Just a general question here, with maybe a sprinkle of heresy thrown in for flavor…

Two things which, to my knowledge, are gospel in UE5: Lumen prefers small, simple, modular meshes over large complex ones; and you should avoid overly heavy and complex collision geometry.

But… that doesn’t appear to be panning out for me in practice. Let me explain:

I made a big battle arena map, roughly 200 meters squared, packed with dense vertical architecture. I spent the last two weeks in Blender separating all of the pieces into smaller meshes and creating custom UCX collision for everything. It was pain.

Then, for giggles, I merged the entire level into one big mesh, imported it back into Unreal, and just used the dreaded (gasp!) Use Complex As Simple option for my collision geometry. The result: My framerate was not affected at all. I’m getting the same performance from what amounts to a thirty second copy-paste job, that two weeks of misery yielded by trying to handcraft UCX and breaking things up into reasonably sized meshes. What gives?!

On top of all that, I will need to do a complete reworking of the level in the near future, and now I’m faced with the question: Is it actually worth it to break my level up into smaller pieces, and make custom UCX meshes, or is that not something I necessarily need to bother with going forward? More to the point: What kind of pitfalls may be waiting in the wings for me if I don’t do things the hard way?

Hi Ianu_Gor,

If you’re getting better performance by merging them all - then it means you’re not optimizing them fully - you can get slightly better render performance with smaller objects and collision etc is faster - culling is easier and memory footprint is smaller:

If performance is the same, it means the bottleneck is else where, and you might see performance differences once that bottleneck is addressed.

Lumen also looks better with broken up meshes. Screen space lumen can hide that a bit, but will still show up as screen space lighting artifacts.