Join split parts from the same surface


How to join these back together? These have been same surface before.

Thanks :slight_smile:

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Hi @Wagner,

Can you share the file?

Do you mean actually join? Because thats just _Join

But you could also mean merge, then there are 2 options.
If the surface is flat, you should be able to use: _MergeCoplanarFace

If the surface is rounded it might be easier to redraw the object.

Hope this helps.


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If both are parts are from one original surface:

  • DupBorder both parts
  • Use Split/Trim with the results to remake the entire outer border curve into one closed loop
  • Untrim the larger surface (you can delete the smaller one)
  • Re-trim the untrimmed surface with the unified border


I’ve made it thousands of times like Helvetosaur wrote. I don’t like it at all. Just wanted to make sure there is no better way nowadays.

Yes Martijn, MergeAllCoplanarFaces is great tool which I use very often. Just wanted to know if there is some similar command for nonplanar surfaces…

Just wishing some kind of “untrim” inside of trimmed edges without it untrims the whole surface.
Command to be something like “Untrim this “hole”(green) with these (red) edges”

Thanks both :slight_smile:

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Well, there is ReplaceEdge which will allow you to delete certain edge trim segments, but Rhino has no knowledge of what the original trimmed edge was before. You can always try the ReplaceWithCurve option in that command if the missing piece still has the corresponding edge curve that you can use.

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Yes, in this case ReplaceEdge with ReplaceWithCurve using the shared edge between the two surfaces should be the quickest way to “merge” these twosurface parts

Thank you everybody :slight_smile:

You can also use xMergeFace / xMergeAllFaces | Food4Rhino ,
but the faces will not merge if the underlying surfaces are inequivalent NURBS, e.g., shrunk after being split, and do not have RhinoCommon-recognized analytical shapes - cones, cylinders, planes, spheres, and tori.