[arty-fishL]

Okay, so I've got textures working.
Follow these steps to fully convert an object with textures from Paint3D to Alice...

1. Create a folder for just this object and its files, this'll organise it better.
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2. Make, download or open your model in Paint3D.
3. Go to the menu and choose "Export File".
4. Choose "3D - 3MF" (this option won't show if your creation is only 2D).
5. Save it to the folder you created.
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6. Start 3D Builder.
   
7. Click "Open".
8. Click "Load object".
9. Choose the .3mf file you exported.
10. See note below.
11. Go to the menu and choose "Save as".
12. Change the "Save as type" to "OBJ Format (*.obj)".
13. Save it to the folder you created.
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14. Start Biturn.
15. Choose the folder you created in the left pane.
16. Choose the .obj file you exported in the middle pane.
17. Change the "Destination format" to "3ds max ascii (.ASE)".
18. Click "Convert !".
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19. Start a plain-text editor, such as Notepad or Notepad++.
20. Choose the Open File option.
21. Locate the .ase you created.
22. (In Notepad you need to change the "Text Documents (*.txt)" option to "All files (*.*)" first).
23. Find and Replace all ".TGA" with ".PNG" (without quotes, case insensitive).
24. Save the file.
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25. Open Alice 2.
26. From the "File" menu choose "Import...".
27. Choose the .ase file you edited.
28. It should import, with textures, without error.

Note: 3D Builder seems to show this error message in the corner when you open a 3MF file from Paint3D:

Just click it. I'm not sure what difference it makes. And I'm not sure how one Microsoft app can improperly export a model for another Microsoft app.


tl;dr Open the .ase file in a plain-text editor (Notepad) first, find-and-replace all '.TGA' with '.PNG', save it, open it in Alice.