Hello, could you post the .fbx file you used in the demo, to have a reference point? Also, are you certain that this file contains the right information? As in, does opening it in another software show different results ?

Also, can you explain what you mean by broken normals ? On what you sent, it seems like the problem is only the hard edges.

Hi, the problem does indeed have to do with hard edges. Hard edges and the normals go hand in hand. Having good normals when importing does not mean anything if when you disable the locked normals all the shading goes bad (because of the missing or wrongly placed hard edges).

Here I will attach a blender file containing a part of the model you saw previously. It has 2 collections: the original import and one where I fixed the shading. Feel free to test exporting the fixed version and importing it again. 100% of the time you will have randomly placed hard edges.

This is apparently an issue with how smoothing data is handled when importing fbx. If you exported the fbx file yourself, you can use the "Edge" smoothing option in the "Geometry" section of the export, which will correctly export sharp edge data.

Otherwise, please add more details about how your fbx file was created : 3D software (with version), export options, etc.

This FBX is created by RizomUV with the default fbx preset.

Tested in Maya 2020 the file opens up perfectly without any missing hard edges or extra ones.

I also tested exporting the mesh from blender with the "edge" smoothing option and I no longer get extra hard edges when importing FBX fiels exported from blender. Thank you for that!

The issue with the FBX exported from RizomUV still stands.