Hi,

I have a project coming up where I will model an object in Blender as Subdivision Surface with sharp creases and then want to convert the result to NURBS for further preparations for injection moulding and adding mechanical detail.

I did this in the past with Fusion 360s internal T-Splines, but would prefer to avoid Autodesk.
Rhino 7 came out a while ago and it does it perfectly, but I'd rather use MoI if possible and would update to version 4 in an instant for that feature.

The problem is, that open seams in the imported obj work for non-crossing edges very well, I could totally use the result.
But when there are three or more open edges, I get holes. This was an issue in the old importer for v3 already and seems to be exactly the same in v4?
So my question is: has anybody found a workaround or viable technique to get such edges/corners to work?
I wouldn't mind if I had to do a bit more work, but so far I didn't come up with a solution myself and didn't find anything with the forum search, although I guess it's a common problem.

I also tried the double-edge approach where each edge that needs to be sharp is comprised of two edges that have no distance to each other. That kinda works, but creates a rather ugly mesh.

What also semi-works is to subdivide the mesh with the creases very highly in Blender (like 5 SubD-steps), apply the SubD and import that fine mesh into MoI. Again, this creates sub-optimal heavy meshes.

Thanks for any pointers!

Tom

This is the result from Fusion/TSplines:


This is MoI with open edges: