Grasshopper smooth brep join

Hi I’m trying to smoothly join 2 closed breps. Think 2 different sized cylinders intersecting with no crease. Kind of like a super smooth weld on a high end bicycle. What would be the best way to go about this? I’d like to be able to control the curvature of the joint as well.


// Rolf

BlendSrf would be a welcome addition to the GH Surface components

You perhaps already have your own component, but if not, perhaps this one would be useful, for you? (Save the component as a UserObject to reuse it in other GH definitions): (12.9 KB)
Edit: R1.1 Srf seam BlendSrf (29.0 KB)

This component sometimes works with only the breps attached. Default curvature = Tangency. Find the right edges using the sliders.

The component may need options for flipping the blend edges, and also the seams may sometimes need to be moved, but for a start… :slight_smile:

// Rolf


Using just grasshopper components you could also create a network surface… (29.8 KB)

Hi Martin, I had thought of that, but the shape of the Breps I need to connect doesn’t allow for that.
I really need to generate a surface based on the continuity of faces, and not edges.

By the way, I’m amazed that you could use blendCurve with a closed curve as input. It looks like some kind of hack, or there is something to BlendCurve that I don’t understand…

These are the Breps I want to make blend surfaces for, in order to make a closed solid with tangent continuity :
Blend that.3dm (1.1 MB)

Hi Rolf,

no, I don’t have my own component. I use Grasshopper because I can’t program :slight_smile:
Thanks for your component !

Rhinocommon in R6 has Blend Surface:

It’s funny you should be the one to mention this, because the first place I went looking for a BlendSrf component is Pufferfish, only to see it was cruely missing :wink:

only to see it was cruely missing

Because I didn’t stop supporting R5 yet :smiley: (and also I find it in general a tough thing to use parametrically, look at all those input requirements) I think @TomTom had a blend surface in his plug-in back in day.

Edit: actually that method is what @RIL is using in his component. Ive just always found that method difficult from a general user standpoint because selecting correct brep edges can be annoying and hard to predict. I also don’t think it works on trimmed edges.

You are right, @RIL 's component doesn’t work here (trimmed edges) :

By the way, I wonder why the “Brep Edges” component doesn’t output the edge indices…
In spite of the “Edges from” GH components which should allow to cherry pick an edge or set of edges, I also find that quite cumbersome, but that’s not a reason to try !
We just need smarter ways to segregate edges, or at least fix those that are buggy like the “Convex Edges”
@DavidRutten ?

I wonder why the “Brep Edges” component doesn’t output the edge indices

If you use “Deconstruct Brep” then the order of the Edges output list would be equal to the indices. It would be nice if Brep Edges also output indices yes.


Gulp. :flushed:

Trickier than I thought. I’ll have to take a deeper dive…

Edit: Looking for a better approach…

// Rolf

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Contact Pierre - Yves Cousteau for the proper equipment

Can you post the geometry closest to the trimmed edges? I have no problem finding and blending trimmed edges, so the problem must be the Polysurface thingy, right?

If so it only means that one must look around and examine all adjacent surfaces and pick the edges that connect to the previous one and stop when arriving at the initial edge again.

That should be doable (I actually did something like that a few months ago). But just to be sure I know the real problem I’d rather test it on a slice of the geometry closest to the edges concerned in your picture.

// Rolf

Nah, I don’t use wet suite. The ol’ usual tools should suffice.

// Rolf

What do you mean ? I posted the two polysurfaces :
Blend that.3dm (1.1 MB)
Not sure what you want…

Ops, I missed that post. Thanks, I’ll take a look at your file asap.

// Rolf

Amazing community… Neglecting gift-shopping on the Sunday before Christmas to help out a fellow member :star_struck:

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Liberated from gift-shopping… :wink:

// Rolf

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