Filleting issue

I know there are numerous discussions about fillets dotting around the forum…

Just curious to know if this (simple) example will be improved upon in WIP??

This is really just a question about creating the fillet on all these edges in one operation. I know how to treat this manually when it does occur.



Fillet issue.3dm (761.8 KB)

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You can get a closed result by first making the smaller fillets separately. Not sure if this is what you had in mind though.

Fillet issue_SG.3dm (1.5 MB)

or maybe this one (distance between rails option)
Fillet issue_SG2.3dm (1.5 MB)

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Thanks @Gijs I would like a rolling ball fillet of equal radius!

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a rolling ball fillet of the same radius will go in one go, depending on the radius. But in your example, you have different radii

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Yes, you’re right. My example fails using the distance between rails type.

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Your object has a few kinks / imperfections. It’s not symmetric. To be able to fillet and maybe other things that follow, I think you’d benefit from reconstructing the object from scratch, on the origin.

I used sections and split parts of your object and the BlendSrf command set to curvature. 1 on the top surface and 0.4 on the perimeter in the XY mid plane.

fillet.3dm (2.1 MB)

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Thanks for the suggestion @martinsiegrist

I would like to be able to fillet as I’ve made it though… I want control of the side wall thickness, then to soften the upper and lower edges.

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Ok, even then I’d suggest to create just one of the two objects. It needs to be closed before you copy / mirror and boolean union the two objects. Then fillet.

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Yes, that was my workflow for that. It works with a ‘rolling ball’ type’, but fails with a ‘distance between’ type…

What radius are you looking for?

Here’s your object cut in half and mirrored twice. Then boolean unioned and filleted. I rebuilt two surfaces with Sweep2.

fillet.3dm (1.8 MB)

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The original intent is actually where the 2 shapes are aligned and not overlapping.

Like the one on the right side.

This is the result (small hole at the y-junction…
Fillet issue3.3dm (728.3 KB)

Model attached too.

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Yes, that’s how I normally do this (for the last few years!). But to my point, I would like this simple example to solve in one step!

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Appreciate that the surfaces not great, but the edges are continuous without kinks , so I would expect it to work…

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I think this will always fail unless you cheat a little bit and move the two objects a tiny bit towards each other.

Here 0.05 mm off center:

fillet.3dm (1.7 MB)

PS: Fillet in one go…

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Hey @sach A one step process is probably not going to work for this model.

you may want to review the pipe trim trick. It’s often the answer for fillets that won’t do what you expect due to some underlying geometry issue, and offers a lot more finate control than do fillets.

video below.


Thanks @theoutside yes, I’ve used this trick also (for years). I was really wondering if this simple scenario for automatic filleting will work in one go in rhino 8….

Cool, It’s a good one that a lot of folks don’t know.

Sadly, what you say is simple is actually not… I’d have to point you to the math folks for a more intelligent answer, but scenarios like this are problematic for surfacing on a number of levels. I’m not a math guy so I’m not even going to venture an attempt other than to say what appears simple here as drawn isn’t actually very simple. BUT… if you’d permit me to do so, I’d love to share this model with the math folks to spark a discussion about how we can do this better.



That corner is quite tricky. External edges transitioning into internal ones, 3-way corners etc. appreciate it’s complicated !

Absolutely, go for it.

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