Why is my lighting/build performance dropping drastically after adding assets in Unreal Engine 5?

Development Programming & Scripting
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Hi everyone,

I’ve been working on a project in Unreal Engine 5, and I’ve recently run into a performance issue that I can’t seem to figure out. Initially, everything was running smoothly, but after I started adding more assets (meshes, materials, and some lighting adjustments), I noticed a significant drop in performance, especially when building lighting and during real-time preview.

I’m not sure if the issue is related to improper asset optimization, lighting settings, or something else entirely. I’ve already tried reducing shadow quality, adjusting LODs, and checking texture sizes, but the improvement is minimal. I’m also wondering if this could be related to Nanite, Lumen, or project scalability settings, but I don’t fully understand how to optimize them properly.

Has anyone experienced something similar? What steps would you recommend to diagnose and fix this issue? Any advice on best practices for maintaining performance while working with larger scenes would be greatly appreciated.

Thanks in advance for your help!

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It’s very hard to diagnose this sort of thing without more information.

How large is the level? ( range: like the demo level → wide open world )

Are there a lot of meshes? ( < 100 is not much, 5000 upwards is starting to be a ‘lot’ )

Is there a lot of foliage, PCG: trees, rocks, grass etc?

How much have you tweaked the lights ( range: moved the sun → added 500 point lights / mega-lights )

Regarding building light, you only need that in very specific circumstances. Things like targeting very low power systems like older phones, or making arch-viz pictures etc. Otherwise, you can just use the default lighting system.

Generally speaking, backing out the additions you have made would be a good route. Or start again, and keep your eye on the performance to find out what specifically is causing the problem.