Getting rid of "seam edges" in developable curved surfaces?


This is a problem I’ve been wondering about for a while. I’m currently modeling handrails to be sent to a fabricator. Due to complications in the pipe function (the curve being piped is doubly curved at certain moments and has numerous changes of direction) and Boolean Union’s occasional unreliability I was forced to combine two intersecting objects by Boolean Splitting them by an arbitrary cut plane running through each object and then Boolean Union’ing them. You’ll notice in my photo that the isocurves in the pipe don’t align. I know for a fact that the surfaces in question are perfectly aligned and continuous such that they could simply be one surface. Is there any way to get rid of this unneeded seam edge? It is distracting and sometimes unclear. In this particular case the geometry will work fine regardless of the seam but there have been occasions where such seams cause problems for me. I know that it is possible to merge two continuous, intersecting planar surfaces so that the they don’t show anymore.

I’m essentially looking for the equivalent of “MergeAllFaces” but for developable curved surfaces. Thanks.

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Hello - please post the objects before this bit,

including the curves and splitting plane

I’ll see if I can come up with a workflow that makes sense. To answer your question more directly, there is a MergeSrf command, but this requires untrimmed edges (possible, maybe, in this case) and also combines the structures of the inputs in ways that are not always very ‘nice’.


Pipe.3dm (348.8 KB)

I don’t have the whole curve anymore, but here’s the model with part of it. This curve would pipe correctly if attempted, but the original one didn’t, hence the convoluted modeling process.

Like I said this particular model is sufficient for what I need it for today, and I’m really looking for any commands/processes that will merge curved surfaces in the same way that “MergeAllFaces” merges planar surfaces. I’m a little confused as to why that appears to not be an option.

Hello - in this case - linear curves, cylinders sharing an axis and radius, you can delete one bit:


UntrimBorder the other:


Move, or ExtendSrf to create an overlap:


and Trim with the miter edges:

and Join. But, still how you got here is what I’d like to fix if possible - I don’t follow the workflow up to splitting.


Yes that works in this case. Thanks for your response. I will keep that technique in mind next time. But I still wonder if there is any way to merge curved surfaces posthumously instead to get rid of the seems. This particular geometry is not the best example, but it is often not expedient to rebuild the surfaces altogether.

Hello - merging co-cylindrcal, co-spherical, ‘co-conal’ surfaces as well as co-planar ones should indeed be possible and is on the pile.


Great! Good to know.