When blender is exported as a Babylon file, the part of the clothing model turns black


Why does this happen??
There’s nothing wrong with the model in blender, but when you export the Babylon format you get a partial blackening.As you can see in the picture.There is no problem exporting obj or GLTF,When I add the “normal” image, the part will be black, just like the arm part.The uv of the model is ok.I also recalculated the normal direction when I exported to the blender, but it didn’t work.
What I’m going to do is I’m going to take an obj format and convert it into Babylon format in blender.There were some mistakes.Exporting to GLTF is not a problem, but I need the Babylon format.The bundle contains model resources in different formats.
https://www.babylonjs-playground.com/#JUKXQD#286
https://www.babylonjs-playground.com/#JUKXQD#288

Pinging our blender gods (@gryff / @Vinc3r)

Can you please share your model

Does your materials using gltf exporter convention, especially color space in texture nodes ? glTF 2.0 — Blender Manual

Thank you very much.I have uploaded babylonian and obj formats to the playground, but I am not very familiar with the playground.The image resource of the model is not loaded. The image and model are in the same path.
https://www.babylonjs-playground.com/#JUKXQD#286

https://www.babylonjs-playground.com/#JUKXQD#288

Thank you very much.My main goal is to convert obj to Babylon in blender, no problem converting to GLTF.After converting to the babylonian format, there is a local blackening problem.If you are interested, you can have a look at the model on the playground.
https://www.babylonjs-playground.com/#JUKXQD#286
https://www.babylonjs-playground.com/#JUKXQD#288

The thing about edge cases is that there are infinite of them XX

I think issue is on Blender side, can you share you object as .blend?

A good starting point is to upgrade to the latest exporter. Your .babylon file shows

{“producer”:{“name”:“Blender”,“version”:“2.80 (sub 75)”,“exporter_version”:“6.2.0”,“file”:“M3.babylon”},

There have been changes since related to materials. This could likely be related. Also, post your log file afterward.

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Is your geometry triangulated or is it quads? I’ve had this problem when I let the exporter convert my quads to Tris.

But that might not be what you have going on.

The solution for my case was to triangulate it prior to export so the UV coords are under control.

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Is something lost transforming quads to tris?

Is there hardware dedicated to quads or something?

It depends, I think we might have an caveat in our exporter on the way it triangulates because I have seen this be the fix several times.

Thank you very much for your answer!My original model was a triangle, and then I tried to change it to a quadrilateral, and I changed it once, and it was normal, but if the quadrilateral was irregular, it would still be a problem, but it would change