Can't turn a surface into a curve?

Hi, I’m trying to turn a certain surface into a curve, but I keep getting:
“1. Data conversion failed from Surface to Curve”

No matter what I do.

Screenshot 2021-06-12 132434
This is the surface.

surface to (236.5 KB)
This is the definition holding only the surface. Below there’s a more complete file.

I’m getting pretty far otherwise, but I haven’t been able to really get this working. Normally some Googling will help me further, but in this case I’m stuck.

This base curve was created by doing this: (316.3 KB)

I think the second GH definition shows more of the needed data, so I figured I include it.

Anyone has a clue?
Thanks for your time, it is much appreciated.

PS eventually I plan to fill the surface with a hatch pattern. But I’m wondering how to make the hatch with the resulting curves. I have also manually created a test and the hatch patterns seem to fill each individual curve instead of seeing them as ‘holes’. Any clue how to make that work?

Feed your surface into a Deconstruct Brep compontent. The edges are the curves you look for.


Join the curves and feed into Pattern Hatch component to get it hatched.

Select from Pattern with what pattern to hatch

surface to (235.9 KB)

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Any surface that has holes, as yours does, will have more than one edge curve.

It’s often necessary to Join Curves using Deconstruct Brep ‘E’ (Edges) to avoid fragments of edge curves.

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Wow, this is absolutely perfect. Thanks. I was using the CreateHatch component from the Human package. It works really well with this as well, however I now see it’s not even necessary.

I have run into new issues though and will write up a new post with example file to explain the issue and see how I can deal with that. (I have multiple shapes on top of each other now and each shape needs to be cut out of every shape that lies underneath it, so I sorted all shapes from big to small, since the smallest ones have to be on top, but I’m running into a bunch of issues with having the shapes being cut out of all shapes that are underneath it).

Very useful to know about Deconstruct Brep. It’s so much fun to get deeper and deeper into Grasshopper. Often my workarounds are more complex than they have to be.

Once again, thanks for helping me on my way!

Thanks, the join curves makes absolute sense! I see Nathan added the join in the second example as well.