5.4 - Exporting scene as gltf: warnings that might cause a crash in blender

Development Pipeline & Plugins
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Hello,
I’ve made a scene using Megascan items only. I used some foliage, but merge it as a Static Mesh. So I only have Static Mesh. I heard that glTF was the way to go to export a whole scene. It’s a little one, tho, a size of a 50*50 plane. Yet, I have (a lot of) those 3 different warnings:

1 - Maximum value (-1) used in indices accessor for mesh SM_CF_TreeFirLarge_A (section ), this may not be supported on some glTF viewers

2 - Material MTL_CF_TreeFirNeedles_Small uses mesh data from SM_CF_TreeFirSeedlings_C but the lightmap UVs (channel 1) are nearly 100% degenerate (in mesh section 0). Simple baking will be used as fallback

3 - Unsupported shading model (Two Sided Foliage) in material MTL_CF_TreeFirBranches, will export as Default Lit

And then, when I try to import it into Blender, half the level is loaded and a python error occurs. I suspect this is linked to the first error, but I am not sure. I found pretty much nothing on Google about that (relative to UE). Do you happen to know how to fix these warnings, what to look at?

BlenderError
BlenderError839×581 114 KB

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Hi, this problem has been bothering me for two hours. I think I have found a temporary solution, but I don’t know why the source file has this issue. A more specific explanation still needs to be answered by experts
Firstly, identify the problematic SM_CF_TreeFirLarge_SA; Then, export it to a new location and import it again, so that my Unreal error disappears. I think this is related to the normal direction, but I can’t find any explanation. After exporting the problem grid with FBX, clearing all normal data, and then importing it back (which would damage usability), I replaced the original file of the static grid and re imported it, which would also cause this error to disappear
Hope to help you.

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I found maybe there are some invalid mesh cause this problem, check your staticMesh for some empty mesh.