Recreated a .umap and its less than 1/10th the original size?

I have a small startmap as a loading environment. It’s small so the game loads up quickly. But over time as i have worked on the map it has increased in size. Last time I tested, it was 40MB. and took longer than I had hoped to load when cooked.

So… I created a blank new map, copied all the actors across, added the level blueprint code, and rebuilt all the lighting to ensure it represented the same state. Since I had instanced foliage which I was unable to duplicate, I had to manually recreate the foliage to look very similar. Luckily not much. So now it looks and works identically to the initial map.

Old map - 40MB
New map - 1.4MB


I cant find any difference… and this is worrying for me… is there garbage building up in the umap file?
Is there any way to easily enumerate the contents of a umap and see what might be different?

I have other MUCH larger maps that would benefit from this treatment… but they have a lot of foliage… and that’s a lot of rework…

I haven’t seen any “map rebuild” or “clean” functions… thought this happened automatically.

Anyone can help?

Just further to this… looking back through perforce history on one of my larger maps… and the size jumps around a bit… at one point it was 280MB then it jumped down to 80MB and has been there for a while… I dont recall making any obvious reduction in map content to that extent at that stage… in fact between those two version i as actually adding stuff…?

It could be lightmaps from baked lighting, those really add to the map size.

Yup, that was my first thought, but both have been baked.