Trying to join 3 surfaces

I can join two in any combination but not 3 if the edge lengths are the same. Must be something simple that I am missing. Please see attached.Join3Surfaces.3dm (59.0 KB)

can’t do that… it’s a non manifold edge.

you can do this-

but not what you are showing

Thanks for the help!

Would you be able to post the file so I can download and look at the geometry?

You can make a T joint with NonmanifoldMerge


its a simple t shaped planar surface extruded into a solid. Join3Surfaces_kfix.3dm (146.3 KB)

Thanks. worked like a charm. Interesting that I can get it to work with a regular join if the surface size does not match like the one on the left.Join3Surfaces.3dm (66.1 KB)

to be clear, 3 sided joints are a bad idea for modeling unless you are doing something very specific.

Thanks for the warning!

I am just in the process of evaluating Rhino and walking through a bunch of the tutorials so this is just for the learning.

Kyle: While you are are in the house, do you have an idea of why BlendEdge is giving me a different result from one side of the radio to the other?BlendEdgeConsistancy.3dm (581.7 KB)

NonManifoldEdge ranks with JoinEdge in the list of commands likely to cause downstream problems. I’m suprised Pascal even admits it exists. :grinning:

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I’m not Kyle and it is best to ask about a new topic in a new thread.

The blend surfaces are between trimmed edges. Try untrimming the surfaces. Then Split the surfaces using the isocurve option and Shrink the surfaces. Then use BlendSrf between the untrimmed surfaces.

I think that I take a different view of this. Transparency is not a bad thing and users do have to take responsibility for the holes they dig.

I’ve added a grin to my comment above.

Non-manifold edges cause problems with many Rhino commands ranging from commands not completing to obviously incorrect results to subtle but wrong results. The latter can be the worst type of hole to fall into because you may not even reslize you are in a hole. My opinion is non-manifold edges should be avoided if at all possible.

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It all depends on input… it looks like the gap was caused by the surface not being able to extend automatically and retrim… no problem, simply extract it, extend it manually and trim it manually.

I tend to worry less about how it happened, and focus on the most efficient fix so I can just keep moving forward.

In your case here, some extract surfaces, some extends and some retrim/ rejoin and you are back in the race.

Kyle; thanks for the reply.

I would like to say I have been viewing your videos along with a host of others supported by McNeil and would like to send my appreciation for all your efforts to make Rhino so clear and accessible to the user community. Your emphasis on the tool as just another artisans clay to create tangible outcomes is inspiring.

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