Blender to UE5 - recompute normals issue

Development Asset Creation
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1

I’ve been trying to import some assets from Blender into UE5, and noticing issues with the normal maps. Specifically related to the mesh normals. These assets were fine in Substance Painter, as well as Unity.

After digging around with various import options, I found that turning off recompute normals & tangents (as well as weighted normals) seems to fix things.

My workflow is fairly standard. Low res meshes get smooth shaded, UV mapped, and then edges around the islands are hardened. The mesh is exported to substance with a weighted normal and triangulation modifier (these get applied to the mesh on export). Normals are set to “Face” in the export. From what I can tell, Unreal is overwriting the weighted normals with it’s own, and breaking the tangents for the normal map in the process.

I guess my question is if there’s a better way of working around this. Am I messing something up by not letting Unreal recompute / modify the normals?

2

In the import settings there is a specific option to select for importing the right normal values.

Generally you set this once, and you even forget that its an option. Which is why i cant remeber what you should set it to…

Your flow seems pretty much spot on.
The big issues are:
Do not ever allow the engine to triangulate for you.
Do not allow the engine to “generate lightmap UV” for you.

Matter of fact, for a good pipeline the standard behaviour is the engine doesnt have to do anything for you.
(And the only thing you can’t control should be computing distance fields. Which I really wish i could just provide so I’m not at the mercy of the engine’s stupidity)…