Making a rounded closed brep starting from two trimmed surfaces

Hello everybody,

I’m working on my first big Grasshopper project and I’m running into some problems.
The goal of this particular part is, like the title says, to make a closed mesh out of two trimmed surfaces. One surface is the result of an offset of the other surface.

I’m trying to make a closed mesh by taking the wireframe (or the naked edges) and loft them. This last function isn’t robust at all. Depending on the surface, it sometimes works like this.
Sometimes it only works when i rebuild the wireframes with the same amount of control points.

I’d like to think of another way that works with all or as many different surfaces.
Hope you guys can help.

Thanks in advance,
Len (1.1 MB)

It seems you forgot to internalise input surfaces.

1 Like (1.1 MB)

Maybe I tried to oversimplify my problem.
What i actually try to do is giving the edge a certain rounding.

Herefore i make sure there’s a line in the middle which is offset by a certain distance.
I’m trying to loft edge1 with the middle line and then edge2.

I hope it’s clear what I’m trying to do.

Greetings (1.1 MB)

1 Like


there are two options to approach this problem. A. You create a surface in between these surfaces and fillet all surfaces, or B. you create Blend Surfaces in between your two main surfaces.You will also need to create cornerblends. However you initial geometry is really bad. So even if you apply it correctly, you blends/fillets won’t look good or even worse, your tools will fail. Furthermore I wouldn’t use Grasshopper for this job at all! Many surface tools required for this job are missing and unless you are planning to do this a couple of hundred times, there is really no need to do this within GH.

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If I loft the 3 lines (2 naked edges and the middle line) I always get a good surface.
In fact I always get the shape I want, but the only problem is I don’t get a closed brep when I join everything together (the lofted surface with the two existing trimmed surface).

There must be a possibility to use the 2 wireframes and the extra middle line…

Also it really has to be done within Grasshopper as this is only a very small part of the project.


I seriously doubt that! Alone of the fact that those are not joinable is an indication that they don’t even match positionally, not to speak of tangency or even curvature alignment. The problem with railing, lofting and similar is the lack of continuity these surfaces have inbetween each other after doing so.

You further need to simplify and smooth your initial geometry

Okay thanks for the info!
I think I understand what you mean now. Although could you give me some extra tips?

I can’t really do much about the shape of the starting surfaces, not the first surface at least. It’s meant for customization purposes so I don’t get to choose the curvature and shape of the initial surface. It needs a certain thickness and rounding, that’s it.

Thanks in advance!