The problem happens no matter the mapping.
What I did is to map the shape as cylindrical map, then bake it to retain the image shape onto the polysrf and then unroll/smash the polysrf.
The flatten version is correctly keeping the baked material but with surface uv mapping instead of keeping the original UV.
The result is then the entire baked map is stretched on each piece.
Please note that the topic of the same subject is already opened, you can access it in this link:
The Rhinoceros team has been working hard to resolve this issue since 2014. I think I read somewhere they pick specific user-reported broken feature issues only once in a few years to not slow down working on new features. This is because the business development team says the new feature sell not a working feature!
I can’t wait for them to start working on this issue.
Thanks for the added information.
Just for you convenience I can’t access the second YT link (probably isn’t pubblic).
@Jussi_Aaltonen I read the YT RH-79787 comment and I agree that the problem is into the Unroll/smash resetting the UV coordinates during the flattening process. With the KeepProperties=Yes I’m expecting the command to “Keep” the texture as well.
There are currently some issues in how the surface parameter information of the Nurbs geometry is stored in the render meshes. I have fixed one bug (RH-79840) today and will investigate further what has been changed since Rhino 7.
Another work around in addition to Reparametrize is to run ClearAllMeshes and switch back to Rendered display mode. That re-creates all the render meshes for those surfaces. As far as I can tell after that Bake and Smash work as in Rhino 7.