SrfSplit / offset glitch

Hi, I seem to have upset GH and I don’t know how or why.

I was trying to run some curves up and over some surfaces - initially I had a vertical surface, fillet surface and horizontal surface - seemed to work ok except I don’t quite know how to get the corresponding surfaces of each section to match up

eg - the bottom surface is 11 of 21, the fillet surface is 12 of 19 and the top 9 of 13

I guess that needs some clever data management but I don’t know how to approach that.

I thought I would be clever and rebuild the 3 surfaces into a single surface and apply the curves to that - side stepping the issue above - it almost works except something seems to be going wrong with the result - I tried offsetting each split section a different amount and it quite slowly arrives at a very broken result for some of the offset sections

SrfSplit (27.9 KB)

The initial Map to surface seems to not like the curved section - so at a guess I would think it is that, or pulling those curves to the surface that is the issue, but if it is I’m not sure how to solve it.

Does anyone have any thoughts? Is this a simple thing to fix? Should I be sticking with the original attempt and figuring out how to “match” the split sections of the 3 surfaces - if so any suggestions on how to achieve that?


From what I can see, the problem is with Offset Surface, not SrfSplit? But I don’t have the plugin so can’t see what you see.


Using the standard GH Offset Surface, I see it fail to offset some of the split surfaces and instead, makes them disappear. Digging deeper, I see that Map To Surface is giving poor results, regardless of whether or not I rebuild the curves. Quite a mess, all in all, sorry I can’t make sense of it.

I finally got something to work. You’ll have to decide which things I did matter because it feels like a combination of issues. And it’s fragile, easily broken by changing the random ‘Seed’ value or the Rebuild Curve ‘N’ value or the offset domain values or…?

SrfSplit (40.5 KB)

  • Instead of using Edge Surface I used Loft (one of the curve values needed to be flipped).
  • Instead of using your two joined curves for Loft I moved/copied one of them.
  • I applied Rebuild Curve to both of them before Loft.
  • I grafted the SrfSplit and Random outputs before Offset.
  • I added the expression “-x” to the Offset ‘D’ input because it was offsetting in instead of out.
  • I lofted each pair of surface fragments to make “Closed Breps”.

In the end, I did not rebuild the curves that do the splitting.


Thank you Joseph, that’s amazing.
I think it all makes sense - I am definitely don’t seem to have a “grasshopper” brain when it comes to actually making the ideas work properly!