Rhino 8 feature: Surface Fillets

Surface Fillets enhancements in Rhino 8

_FilletSrf has been enhanced with a new dialog that allows you to set the radius dynamically. While changing the radius, the result will update in real time. You now have three fillet options: Arc, Deformable and G2.

Deformable fillets are non-rational with G1 continuity. Deformable fillets of degree 3 have a tangency slider and deformable fillets of degree 4 and 5 have a tangency and buldge slider. These sliders allow you to influence the shape of the fillet anywhere between flat and sharp. When set to default (0), these fillets approximate an arc shape.

Rhino 8 adds 2 new surface fillet commands, _FilletSrfCrv and _FilletSrfToRail. All three commands share the same style dialog. Next to a dialog version, commandline versions of these tools are available.


:thinking: :thought_balloon: k what about systems that have more than 2 srf’s …


I’d expect to be able to trim a surface with the fillet. I tried the new command FilletSrfCrv twice but the fillet does not end on the surface edge.

filletsrfcrv_problem.3dm (143.6 KB)

thanks @martinsiegrist for reporting. I’ve added RH-74735 FilletSrfCrv doesn’t reach far enough to trim surface at certain radii

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Nice! Do you plan to implement the distance between rails option? And to work with multiple surfaces would be great indeed.

Interesing, but far from usable! Who is developing this? Do you have feedback from actual users? Maybe someone who has experience with VSR or Alias?
The nee toll Looks promising, but should be more robust and polished…

I’ve added RH-74756 Wish: FilletSrf Distance Between Rails Option

Please let us what works and what not.

That’s why we make these announcement posts, to get feedback from you and others.

There are still (known) bugs that need to be resolved regarding Surface Fillets in V8, yes.

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Until there’s about 300 hits, then yall will close it :sob:

well done


can you run those upto more than one crv or rail?

I assume you are referring to the FilletEdge thread? In some rare cases, threads are closed, it’s not merely based on thread length. In case of that thread I closed it because it ended up in a lot of off topic discussion. You’re always welcome to start a new thread on a topic.

FilletSrf traditionally has been a one to one surface fillet, the same applies to these new additions. @jim recently posted an awesome script to automate filleting chains of tangent surfaces. I suspect something similar can be done to these new tools eventually.

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I would not count on the script working in Rhino 8. It seems that they have made Rhino 8 no longer able to correctly make rolling ball fillets. Here is a simple example where a 1 mm fillet falls short of making all the way across the cyan surface.
short_fillet.3dm (61.6 KB)

That’s a show stopper.

Also in Rhino 7 and Rhino 8 there are serious problems with the boundary definitions of joined fillet strings. The edges of the fillets are no longer a string of curves with a single end points at each node. This means that every vertex in every polysurface has multiple end snap points. This seems like they have designed it for making trimming and joining surfaces into valid BREPS as difficult as possible. It is no wonder Rhino users are plagued by tiny microedges that won’t join and tiny no area surfaces in their models.

Is the plan to make Rhino just for visualization purposes? If the user wants accurate and correct geometry will the user need some other application to do that?


thanks for sending @jim
I’ve added your fillet case to the tracker
RH-74777 FilletSrf fails to produce a complete fillet

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4 posts were split to a new topic: Join leaves gaps at adjacent edges of joins


This is a brilliant development, love the direction in which this is heading!

One request from me -

Could we please add degree 6 and 7 to the list of deformable fillets please? My aim would be to achieve an arc fillet to under 0.005 mm tolerance but with a more even distribution of control points than the degree 5 fillet currently gives us.

hi Rob, is the result you are after just as creating an arc fillet and running _ChangeDegree afterward? (Edit: well I can answer this myself, because it’s not the same, as it makes a weighted control point structure this way)
I wonder though if we would add this, what needs to be done with the sliders, as they won’t be able to control all the points in >5 degree surfaces.


Ah, just seen your edit - I’ll comment anyway - change degree on the arc fillet ends up with unequal control point spacing as in pic below, so no, not what I’m after.

But (personally) I’m also not looking for a fillet that can be deformed at degree 6 or 7. I’m just after the equal control point distribution as this makes things easier when you have to create manual blends at the fillet terminations.

Perhaps this request doesn’t belong in the ‘deformable’ section, but in the ‘arc’ section as a ‘non-weighted’ option?

Good point about not being able to control the extra points with the sliders in deformable mode - I actually think Rhino would vastly benefit from being able to blend changes above degree5 - using some falloff gradient. This could also be implemented into other tools such as match surf.

RH-74777 is fixed in the latest WIP

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Hello it would be great if you could implement the option to change the shape for both cv rows but keep g1 and g2 continuity.( almost similar to the Blend surface)

because at the moment you will get no curvature for the deformable option. and i have to rebuild every fillet with the blend tool if i want g2 and shape control.

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