Trimmed surfaces solution for next Grasshopper?



Dear David,

In the current grasshopper version, there is no solution to the trimmed surfaces, especially when one needs to evaluate, divide surface, etc…

It would be great if this issue could be solved for the next Grasshopper version. Rhino has a solution for that, the “ShrinkTrimmedSrf” command, maybe grasshopper could have that as well?

Many thanks in advance :slight_smile:


Hi Wassef,

You can use a custom ghpython component to shrink a surface.
Check the attached file below.
It requires ghpython plugin to be installed. (5.1 KB)

(David Rutten) #3

Shrinking will only result in an untrimmed surface if the trimming edges are exactly along the Surface UV directions and the trimmed region is convex. In most cases shrinking will still leave you with another trimmed surface, albeit a somewhat smaller one.

I can add a Shrink component, but I’m worried it doesn’t actually solve that many problems, or at least not anywhere near as many as it seems to suggest. I’m not really sure what a better solution would look like, so maybe it’s the best we can come up with…


Given 4 sided surfaces, Isn’t it possible to shrink the trimmed edge and align/ even out the ControlPoints between the trimmed edge and the opposite edge?

I understand that there are cases when touching the middle CPs would change the surface very much, but in such cases anyone would understand that attempting to shrink the surface wouldn’t be justified anyway.

// Rolf


If it’s a 4 sided surface, you can extract the edges and create a new, untrimmed surface via EdgeSrf. However, aside from the case of planar surfaces, there is absolutely no guarantee that the new surface will correspond with the original.


Thank you very much djorje for your info and link!!
I have already found this solution a while ago when I was researching for it, I guess on the grasshopper3d forum. I was wondering if this could be maybe implemented in the next Grasshopper, and also solving the other issues that David mentioned below.

But many thanks anyway for your input, much appreciated!!

(David Cockey) #7

Yes, if you want a different surface,