Making smooth joints in booleaned and filleted polysurfaces


Hi, I’m having problems at the very last step of a design. I filleted edges to round the borders at the beginning of the process, and later boolean union another solid as one of the last steps. I want the union between these two to be softened. When I (in Rhino 5) use the command Apply Edge softening (because in Rhino 4 the closest I come is fileting edge, but am not able to join that with my solid), my piece goes all crazy, although it does smooth the union. I don’t know how else to make the juncture smooth! Please help :slight_smile:

As you can see in the first picture, the union is not softened.

And in the second picture, you can see that it has smoothed a bit near the bottom, but the rest it has completely backfired and created sharp edges.

The third is after edge softening of the other side, which looks better, but a chunk is taken out of the top of the union of the ring and the other part.

(Pascal Golay) #2

Hi CMo Please post a Rhino file if that is possible- just the object you’re asking about. My guess is this will look a lot better if you set the meshing to a finer mesh - in DocumentProperties > Mesh page, or by setting a custom mesh for the object in Properties.



Hi Pascal,

Thanks for your quick response…i tried changing the properties for the Mesh and it still didn’t work. Let me see if I can attach the rhino file.6 cm kite bottom (ready for print).3dm (758.8 KB)

(Pascal Golay) #4

Hi CMo - there is a little messiness in how the surfaces are put together right there- some fussy little surface fragments that can be simplified - I’ve done that here, and it helps, but there is still a problem with the edge softening, so I moved the ring very slightly away from that junction of lots of surfaces- is that acceptable?
See the ‘fussy stuff’ layer for stuff I replaced. Especially the little tiny sliver of a surface that is called out with an arrow - try to avoid surfaces like that. The top cap surface is replaced by a trimmed plane - much simpler - and the little surfaces at the edge of the ring - one is deleted, not necessary since it is part of the top cap (plane) and one is replaced with a patch - probably I’d do that differently if I were starting from scratch but a patch does OK here- better than the edgeSrf with a singularity that you have in there.

6 cm kite bottom (ready for print)_PG.3dm (550.4 KB)

(Brian James) #5

I found the same issues with some of the surfaces that Pascal did but also tried adjusting the render mesh which is what edge softening uses as a base. Neither helped with the ring in the original location so I’ve filed this as a bug

Thanks for reporting the case.


Thanks guys…as you can probably tell, I’m not a Rhino master by any means, I started learning it over 5 years ago, but I just got back into it and still don’t know half of it and stick to pretty simple functions. So I have a couple questions: if i had printed the piece as I had it before (not with the softened edges and resultant jagged borders), would it have printed smoothly, or are y’all saying that my surfaces were not smooth anyways?
Pascal, even though the union now appears to be smooth without any jagged edges, as you said where you have the arrow, there are still some sharp edges…so it’s still not completely finished, as i’m assuming those will be visible when printed, correct?
Another thing, this is just the first pass for me at this design, so it’s not final and I was going to modify it a bit…ideally i’l like to be able to do it all myself (although I definitely appreciate the help)…do you have any suggestions how to avoid these crazy surfaces at the end, or any other way to get a smooth union? In all honesty, I had to download a trial version of Rhino 5 because I read about ApplySmoothEdges and I wasn’t able to figure out anyway to smooth the union in Rhino 4. Or is there any way to avoid the ‘fussy stuff’ ? I’m not too familiar with meshes, and like I said before, I’m refamiliarizing myself with Rhino and constantly learning, but it doesn’t come easily to me.

Thanks again guys!

(Brian James) #7

If you export the model as an stl it should print fine if it’s closed. The ‘What’ command can be used to see if the model is closed which tends to be the main requirement for printing.

Edit: I checked the mesh extracted without softening and it actually had issues. MeshRepair needed to be used a couple times to fix them.

If on the other hand, you used ExtractRenderMesh when the edge softening was visible, you would end up with an open mesh that wouldn’t print well. You could use MeshRepair to try and fix those issues but it would not smooth the holes and I doubt it would be what you’re after. Depending on the size of the part and the printer used, you might get some softening of the edges exporting the non softened mesh version.

Check out this tutorial series too…

(Pascal Golay) #8

I accidentally left an extra polysurface there- it is not part of the ‘corrected’ brep - just click there and you’ll see there are two objects- delete the smaller one.

Yes, but it involves a) being careful, and b) knowing what to look for to be careful about. One thing that I think is helpful in your case is that trimming surfaces does not remove any of the underlying surface- so for example, on your original, at the top face where the ring is, you have a little crescent shaped surface apparently filling a hole there created by the ring. If you are going to fill a hole in a surface, the best way is to Untrim that edge - no need to add a new surface, which just makes more edges and complexity.

I’d also look at the level 2 training material here, especially (in this context) the part about NURBS topology.