UE5 Is Breaking Geometry On An Imported .FBX Model From Blender (Weird Normals)

Development Asset Creation
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1

I am having an issue when importing an .fbx file from Blender where a part of the geometry in UE5 is ‘breaking’ and I can’t for the life of me figure out why this happens and how to fix it.

See below a screenshot of the mesh in Blender and a shot of the same mesh after importing to UE5.

Screenshot 2022-09-03 at 11.46.12
Screenshot 2022-09-03 at 11.46.12954×848 51.5 KB

Screenshot 2022-09-03 at 11.59.08
Screenshot 2022-09-03 at 11.59.081238×1274 41.2 KB

The mesh in Blender had all transforms, modifiers applied, has all materials applied, normals are all facing outside and the model has a UV.

Here are my .fbx settings when exporting…

Screenshot 2022-09-03 at 12.09.13
Screenshot 2022-09-03 at 12.09.13470×1574 105 KB

I also have zero errors on import to UE5. Here are my import settings…

Screenshot 2022-09-03 at 12.06.21
Screenshot 2022-09-03 at 12.06.21792×1310 73 KB

When I enter the modelling mode in UE5 and go into the normals section, the model appears on screen as it should. However, if I accept these settings or “fix normals”, the model reverts back to being broken in the viewport.

Screenshot 2022-09-03 at 12.37.16
Screenshot 2022-09-03 at 12.37.16626×594 247 KB

The last thing is that I only have one LOD on this mesh which is set to ‘None’ the same as all other meshes in the level which have no issues.

Screenshot 2022-09-03 at 12.42.22
Screenshot 2022-09-03 at 12.42.22858×530 13.5 KB

If any of you splendid folk can let me know if I am being thick and missing something obvious, or if any of you have an idea on what causes this issue and/or how to fix it. I would appreciate it greatly.

Thanks in advance,
Dave

2

U sure it’s not a nanite issue?

3

My friend, it would appear you are correct. If I import the models without building nanites, there is no problem.

I don’t suppose you know why this is or if you could point me in the direction of more info on fixing this issue in the future?

Thank you.

All the best,
Dave

4

not an expert but if you import w non-nanite, then go into the mesh properties in unreal, you can build the nanite version of the mesh from there and mess with some settings. It could also be nanite isn’t really working and it’s displaying the “fallback” mesh, which there are also settings for. The nanite visualization modes can also be helpful.

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5

Hey folks, I found out on my side that UE imports the mesh with no such issue when I tick off the “Remove Degenerates” option. Hope it will help somebody.

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