Converting .c4d (or .max) files to fbx inside Unity/ Upgrading old project

Hello,

I'm trying to migrate an ancient Unity 4.5.4 project to a current LTS (and SRP). The project is from 2014, back when Unity still had a built-in way to read Maxon Cinema's native .c4d-files. (Internally, these files were converted to fbx-files, that were updated automatically when the .c4d files were changed.) All of the 3d assets in the project are in .c4d format. I got the project up and running in Unity 4.7.2 and all the meshes are assigned correctly.

Now, since the support for .c4d-files has since been removed from Unity, I'm stuck with the question of how I could upgrade the project to 2020.3 LTS without (as happened when I tried) losing all the formerly correctly assigned meshes in all the mesh renderers pointing at a .c4d file as obviously the c4d files in don't get converted in this Unity version anymore.
I guess the fbx file that Unity derives from a .c4d-file is stored somewhere and I wonder if it is possible to extract these internally converted .fbx versions of the .c4d files and replace said .c4d files with them without losing the assignement of the meshes in the process. Or if there's another feasable way of upgrading.

If anybody has any suggestions, I'd be glad to hear and try them.

Thanks for your help,

Felix

 

seems that 2017.4 still supports those files, maybe try to get there first
then could try exporting fbx/obj files from editor (there should be some plugins for that)..
pretty sure you'd have to rework the references though..
or if that version is good enough, stay there, unless there is specific reason to use SRP?

*well this seems better, https://forum.unity.com/threads/changes-to-cinema4d-support-in-unity.852511/