Resetting Control Points on a Surface after Trim


Hi All,

I created a lofted surface from a series of curves. Later on after some more editing I decided to trim the surface into rectangular extents as the edges had become too organic. However, now when click the control points “On” they are giving me the original control points from the first lines I used to make the surface (there are some floating off to the side, etc.). This is becoming a problem for me because when I subdivide in Grasshopper it is taking the extents of the original shape, not the current (trimmed) one.

Whats happening here? I’ve never seen it before, but I cant find anything about resetting control points.


(Pascal Golay) #2

Hi BeeCee- see if ShrinkTrimmedSrf does what you need.


(John Brock) #3

It looks like you have a fundamental misunderstanding about NURBS surfaces. The topology of a NURBS surface is a rectangle. That’s what you had when you lofted your original surface.
When you trimmed away all or part of it’s boundary, that new trim curve was added as a modifier to the surface definition. It does not update or change the underlying topology. It just visually ignores anything outside of the trim curve. All the original geometry is still there.

Based on your description, you will need to replace your trimmed surface with one that is not trimmed.
I would detach the trim curve, Explode it, and use the Section command to take slices through your existing surface. Choose curves appropriate to the surface creation command you wan to use. Perhaps Loft or NetworkSrf. Then use these harvested curves to make a new untrimmed surface and delete the original trimmed surface…


Thanks for the replies. I was hoping to avoid recreating the whole surface from scratch, but I guess thats what you’re essentially saying John?

(John Brock) #5

I didn’t mention ShrinkTrimmedSrf since it didn’t sound likely BeeCee’s trim curves were created from Isocurves from the original surface.