Split Brep Multiple Separate Results


I am using Split Brep Multiple to cut a hole I have a couple of issues/Doubt

  1. 6th item in both the branch is showing as open brep I was expecting them to be Trimmed surface!!

  2. I was aiming to extract the 13th item from both the branches is there a simple way to separate the results from Split Breep Multiple like A) the Main Brep B) Trimmed Surface

I saw a simple script from David Rutten where it separates the output as A & B something similar would be ideal in the situation.

Please find the attachments

Could Some one please clarify this issues, Thanks



Split Brep Mutiple A.gh (11.4 KB)
Split Brep Mutiple A.3dm (185.4 KB)

6th item in both the branch is showing as open brep I was expecting them to be Trimmed surface!!

Because it is an open brep, They each consist of two surfaces because they are cutting on a seam.

You can resolve it with the merge faces components (or run the _MergeAllFaces command in Rhino on the geometry before you reference it into grasshopper to remove that seam):

To get an A/B situation when you need to cull an index you can use list item and cull index together to get the A and B of a list:

Split Brep Mutiple MP.gh (13.8 KB)


Thanks for the reply & the solution.

If you don’t mind asking couple of follow up questions

  1. Why in Open Brep there is seam created (is it due to sharp peak at the top!!), is there a way to avoid the seam
    Note: This particular brep was constructed using loft option (Please find the attached)

  2. With respect to A & B option your option is good, but in my case I was aiming for a automatic detection of Open Brep & Trimmed Surface without giving the index manually

  3. With respected to point 1 if we could manage without seam, I would guess there is no need for Merge Face Component !!

I guess something similar to David Rutten script would be ideal, unfortunately it is not working with multiple face breep.

Please find the attached GH file where the inital brep was created.




_Loft B.gh (11.3 KB)
Loft.3dm (63.2 KB)

You just need an understanding of Rhino. This is how loft works. For instance, lofts wont result in trimmed surfaces. So in your case of lofting a kinked top to a straight bottom, there is no way to make that shape without being a trimmed surface or a polysurface of two untrimmed surfaces. Rhino loft logic is set up the way of making untrimmed parts (easier to work with than trimmed surfaces) - So you can just Merge Coplanar faces on the loft.


Ok thanks for the information.