Extracted OBJ meshes using "None" material

[brybrant]

Hi, great work and thank you for this tool!

Sometimes when I extract a model, the OBJ file contains meshes with usemtl None but when I view the model in your renderer I can see the model meshes use the correct materials!

Also.. Some OBJ files contain vertex normals with value "nan". This doesn't seem to break the model, but may be worth investigating.

[brybrant]

Issue:
The OBJ file exports all meshes with usemtl None - even though all of the textures and MTL file export successfully. The 'Log' window pane shows no errors and I can see the model meshes using the correct materials in the renderer window pane.

Steps to reproduce:
Right-click a model in the 'File List' window pane, then click 'Extract File (ID)...'

Some examples of models that always export the meshes with 'None' material ( all from ./doc/stuff.txt ) :
217735 The Shatterer
230252 Pact air ship
543946 Sunrise
543947 Twilight
1299838 Gorseval the Multifarious
1466077 Lion Guard's ship
1749827 rock dragon ( btw the dragon's name is Vlast )
1750500 Anubis ( Awakened Canid )

These are just some examples of models that export with meshes using 'None' material but there is many many more, like all 187xxxx models, all 199xxxx models, and most models after that. This issue seems to affect recent models more than older models. Please let me know if you are able to reproduce this issue. I would greatly appreciate a fix or explanation why this happens. Cheers!

[Ovahlord]

confirmed. Issue reproduced by exporting 1820283 (Balthazar). All materials in the obj file are not assigned properly.