Need help filleting edge

I’m having difficulty filleting this edge. Can someone please have a look and see what is going on? I’m hoping to get a larger fillet than 1mm too if possible…


FilletEdgeNotWorking.3dm (10.7 MB)

This model should be simplified - use 90% fewer control points.
Then the fillets will work.

Hi @samlochner

Just curious, is this a native Rhino file or imported curves to start with ?

Rodolfo Santos

Uh, maybe the model should be simplified but extracting that wireframe isn’t really indicative of that, trimmed edges are inherently dense, that’s not the problem. The main problem is discontinuity between the upper surfaces.

Of course manual filleting with FilletSrf could get this to “fillet,” but reworking those top surfaces would be better. I’m sure you will get a lot of advice but to put it very quickly, it’s obvious that the ‘side’ surface was done first and then the top ‘filled in.’ It would be better to approach it the other way.

Dear @samlochner - what s the next step ? for what do you need the data ?
fillet fails because of the missing tangential continuity - as the other to answers already pointed out.
… i will post a fast solution to get it done the dirty way…

the fast and dirty way to fix the edges - for simple visualisation purpose or going to the evening sun…
use _offsetCrvOnSrf to cut a gab along the edge, that is not fitting well.
do some _untrimAll for nearly all surfaces
use _blendSrf to “bridge” the new gab to get the desired continuety

_trim and _join

_joinEdges (very dirty, skipping document precision)


i decreased document tolerance to 0.01

please also notice, if the surfaces (including the _blendSrf) have a radius less then the _filletEdge Radius, it will fail.

for bigger radius use above workflow with a bigger gab.
for high quality data, you have to rework the surfaces.

hope that helps- kind regards tom

FilletEdgeNotWorking_dirtyfix.3dm (14.9 MB)

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Trimmed surfaces inherit the characteristics of the underlying curves in every instance. Bezier geometry will produce inherently light trimmed edges, while high level curves produce dense surfaces.
High level curves are also much more difficult to achieve tangential continuity with - thus the edges will be a bear to fillet.

This is the case if the trim is an isocurve.


I’m not sure where your comments are headed, but in Rhino, FilletEdge does not care, particularly, how dense a trimmed edge is. It certainly prefers that it be smooth.


Greetings All,

I stand corrected - Thanks for the lesson.

Wow, thanks for all the replies. Got it working.

@tom_, next step is 3d printing

@RodolfoSantos, it’s native curves

Thanks again,

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