I wanted to move a lot of free Blender objects and scenes into C4D. I tried a free IO plugin on Gumroad which could copy/paste between Blender and C4D apparently using FBX. Many times the materials didn't have textures or were referencing ones that were misnamed in the conversion. I decided to try USD instead and it seemed to work better. Full scenes of objects w/materials came across including converted RS materials. While it wasn't perfect as any materials with transparency had that parameter lost in the process, it was better than straight FBX.
I had ChatGPT then come up with a couple of scripts, one for Blender and the other for C4D. The one from blender would simply copy selected geo a temp USD file. In C4D, the script would copy that temp file into the existing scene. I eventually added to it to allow the Blender scene to unpack and write any textures to disk before exporting the USD. That's because some Blender scene files have their textures packed inside the file and it seemed like the USD export didn't grab them. Somewhere along the way with the rewrites I had it do, it decided to export the whole scene (incl cameras). I'm ok with that for now. I also had ChatGPT create an icon for the C4D script. I didn't do one for blender since the devs hate any real customization like putting custom buttons on the UI or other fun stuff (without coding it with serpens). I know you can add an icon in the addon but I hate the UX of the addon tabs anyways.
Included below is the bundle. Install in blender as an addon. You'll find the addon in the addons tabs. Install in C4D as a script. Apply the icon to the script and place the script anywhere on the UI if you want. It asked if I wanted to create it as a plugin but I didn't go that route.
NOTE: This is free. Do whatever with it. During the modifications of the scripts in ChatGPT I specifically told it I'm using Blender 4.4.3 and C4D 2025.2.1. I can't verify this will work on older/future versions of either software. It's the environment I'm using now so I built it as such.
It does make me wonder if some of the old scripts/plugins could be reinvigorated w/GPT to make them work with newer versions of C4D.
usd_io_blender and c4d.zip