Cut and trimmed surfaces control points

I’m fairly new to Rhino and I have a question about trimmed and cut surfaces. I use Rhino for ship modeling and typically if I’m modeling let say a deck or hull girder, I would start with a big surface and would trim it or split as fit. But if I needed to go back and modify it or extend, I try using control points but when I turned them on they’re the control points of the original untrimmed surface I started with. Is there a way to change that to where my new trimmed or cut surface(s) have its own (their) control points?

Only partially.
The topology of the NURBS surface is a rectangle. To get a circular NURBS surface, it is “trimmed”. The original, underlying surface geometry is there.
You can reduce the excess surface by “Shrinking” the trimmed surface.

If I’m understanding what you correctly, you’ll probably want to “Untrim” the trimmed surface to get your trimming curve back, modify it, then re-trim the surface with the modified curve.

Hi John,

Thanks for the quick response, I was hoping for a quicker way than having untrim modify and re-trim. Shrinking the trimmed surface was a great tip, thank you for that. It would make the untrimming process little better especially if my starting surface is a big one.

You may want to try SolidPtOn.


Thank you very much for the reply Sam, that’s exactly what I was looking for.