Fix mesh not loading for 3mf files generated by Bambu Studio

[YoakeNoTenshi]

This is to fix an issue with some 3mf files generated by Bambu Studio as described in #69

Basically the 3dmodel.model file contains references to components defined in other model files. So when it tries to build the build/items the script can't find the sub components in resource_objects and logs the error Build item with unknown resource ID. Sub components are loaded in resource_objects later on but never converted to actual Blender objects.

This fix loads all the models in the 3mf file in resource_objects and then creates all the Blender objects. This assumes all the object IDs are unique and I don't know if that's actually the case.

This was tested with the 3mf file here: https://makerworld.com/en/models/20200#profileId-20736

Before the fix:

After the fix:

[Ghostkeeper]

The automated code style check is complaining that there's whitespace characters on an empty line at line 146 of import_3mf.py. I'll fix that up for you if/when merging, it's a really minor thing.

[HeytalePazguato]

This issue is still present, when will it be fixed?

[Zoupers]

Blender3mfFormat-1.0.2.zip
Here is a modified version for those who came here as a quick way.
File's md5sum is 8c6774ffad93b12b41cc6b6863c5d586

[wancoder]

Blender3mfFormat-1.0.2.zip Here is a modified version for those who came here as a quick way. File's md5sum is 8c6774ffad93b12b41cc6b6863c5d586

Cheers