This has been a bug for months, that requires a work around of deleting the asset, saving, commit to revision control, wiping all trace of the asset, before reimporting, and assigning LODs. If you then need to make a change on the base mesh, LODs will break and you have to repeat the whole process.
Hello @itsanate
we did not manage to reproduce exactly your issue: if possible could you share a video of your repro steps and the 3 meshes you used for the test? At least do you mind providing more details of your different step so we try to reproduce.
Also I do not understand how you manage to visualize the lods in your UEFN. I cannot deactivate Nanite on my static mesh so I always see the nanite mesh and not the lods I imported, even though the fallback vertices/triangle count did change accordingly to the mesh I assigned for the LOD Selected
I did close and restart UEFN, reimport a modified version of the base mesh from the Reimport Mesh option of the static mesh editor: I still have LOD1 and LOD2 with the same fallback vertices has before reimport.
I have linked a recording of my process, and the bug. Here’s a link to the video.
My process is as follows:
Import ‘StaticMesh.fbx’
Open Static Mesh
(Switch collision to NoCollision & UseSimpleAsComplex, and Assign Material)
Save & Close Asset
Reopen Asset
Import LOD Level 1
Select ‘StaticMesh_LOD1.fbx’
Import LOD Level 2
Select ‘StaticMesh_LOD2.fbx’
Save Asset
Switch ‘Set the Level of Detail of the Viewport’ from LODAuto to LOD0, LOD1, LOD2
See the LOD custom LODs switching as you click through the levels
The steps to reproduce the reimport bug are as continues:
Edit original static mesh in Blender or other modelling software, reexport and save over ‘StaticMesh.fbx’
Right click on the asset in the Content Browser and click ‘Reimport Static Mesh’
LODs fallback to Nanite, disregarding custom LODs
Repeat steps 5 to 8
View LODs using Step 10 and 11, to see the custom LODs no longer come in.
My workaround of this bug is to delete the asset from the Content Browser and reimport it, usually with a slightly different name to avoid Revision Control issues (‘StaticMesh1.fbx’ for example).
I don’t disable Nanite, or import via vanilla UE5, it’s all within UEFN. I try to let Nanite do it’s job when I can because it saves me work, but sometimes the power to dictate what the mesh looks like from afar is really important.
As for why LODs may not have been working, I did attempt to record a video of this bug with an asset with far fewer triangles, <500 and I experienced the same issue where the LODs wouldn’t show - but I didn’t even see Nanite fallback meshes as I switched through the LOD levels, so I don’t know what specifically was occurring there.
I don’t feel comfortable sharing the model in an open forum (I’d be happy to privately), but the general setup uses vertex colours (Face Corner - Color) exported in sRGB, and no collision hulls. LOD0 has 936 Tris, LOD1 516 Tris, LOD2 286 Tris.
