FilletEdge fail when going "across" an entire surface?

Have a look at this image:


The result obviously doesn’t follow the preview, by quite some margin at that.

I suspect the reason is because the FilletEdge has to blend across an entire surface (highlighted in red below) within the polysurface:


Is this expected behavior? (Just curious for future reference.)

Does anyone have any suggestions here apart from the long workaround of untrimming both surfaces around the fillet and trimming and joining them together to perform the FilletEdge (without TrimAndJoin) and then trim to integrate the middle fillet once more?

chord.3dm (298.8 KB)

(Oh, and I’m using DistanceBetweenRails at 2mm for this.)

yes, filletedge doesn’t allow other adjacent surfaces to work. in this case you can use FilletSrf and rebuild it manually. is tedious but it works that way

Something like this:

then you can use MatchSrf

Could this be written as “filletedge doesn’t allow other adjacent surfaces to be swallowed entirely by the fillet, even though there’s other g1/g2 surfaces beyond it that it could continue to match onto”?

If so, then I understand. If not, then I’m still curious about the limitations. :slight_smile:

Also, I see you do an edge match instead of closest points. I tried asking in a different thread but didn’t receive a straight answer, so I’m guessing CurveNearSurface, that is surface projection (pull), doesn’t work across multiple surfaces in Rhino?

Usually, projecting onto a surface and then trimming produces much cleaner results than attempting to match a trimmed edge and a surface at the same time…

the name of each command says it. filletsrf works on the surfaces no matter if they are touching or not while fillet edge works on the edges, other surfaces are not counted.
english is not my language, sorry if it is not clear enough.
I made edge match because I have trimmed surface to work with and I’m still not used to the closest points thing


I did the following which seems to produce a bit cleaner result:

  1. Create outer corner curve and trim.
  2. Create blend surface manually.
  3. Match to outer corner trimmed edge.
  4. Rebuilt blend surface to make cleaner hull (while staying within position document tolerance).
  5. Untrim outer corner.
  6. Trim outer corner using blend surface instead.


I mean it’s not perfect, but it will have to do for now, and I think this surface will offset easier as well when I add material thickness to the part.

Extracting the surfaces and applying “Rebuld edges” before using “Match surface” gives you far cleaner result.

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