Friends Don't Let Friends Fillet Surface Models

This is not an attack. I see the fillet improvements in V6. I just think that FilletEdge is not a good fit with surface modeling. I’ve heard people complain about how much better fillets are with expensive solid modeling apps, but I’ve taken my NURBs into those apps, and the fillets fail there as well.

Speaking for jewelry designers, even the good modelers create nasty corner conditions. All of us start modeling in Rhino using some plugin’s automated workflow that creates edges which are best described as a bowl of bananas. The error rate of fillets will always be high enough that we stop attempting to use it.

Instead of asking for fillets to be better, I accept the complexity of the problem and ask McNeel to come up with something entirely different. Maybe something quick and dirty, like a bulletproof way to knock off a corner of a closed polysurf without perfect G2 continuity at an exact radius. Or look at all the ways people solve this problem manually and creating a workflow that speeds up the tedious nature of the process.

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the pipe trim trick will be your best friend here. use a pipe to trim a hole of whatever diameter you choose and then use blend surface to fill the hole- that’s the quick and dirty way to knock corners off.


Trouble is, as you can see with many NURBS surface creation questions here, that very often, the initial curves and then surfaces are overly complex or not of a good quality, which then leads to problems further down the line; filleting is just one issue that rears its ugly head again and again.

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Ah fillets…so many bones…


The piped trim workflow is a perfect example. I’d like to see McNeel invest in making Pipe editable so we can adjust the radius or add handles similar to fillet edge. Pipe could also incorporate RebuildCrvNonUniform so the trimming geometry is lighter, smoother (eliminate G0 crv seams), and easier to edit.

Yes, complex geometry is a problem for junior modelers, but I’m strictly speaking to complex corners. There’s nothing you can do about that. Surfaces have four sides, and a feature has to go where it has to go. My output goes through investment casting which does not tolerate sharp corners.

I learned Class A modeling when I bought VSR a few years back, and I always start with single span geometry. Losing the VSR plugin has been painful moving to V6, but having history on MatchSrf has been excellent.

How hard would it be for McNeel to roll that into a single command?

pipe trim? probably not a great candidate for making it a tool… it’s got a lot of conditions that come up that need to be modeled by hand (like self intersections on large pipes in small corners) It’s more of a workflow than a tool in my mind…

It would not work as a single command but could be supported as a workflow. The pipe command could be updated to allow the radii to be edited (or handles added) after the initial construction. The handles could also generate a perpendicular blend between the trimmed surfaces at each handle for use in BlendSrf.

The point is, there are ways of empowering us which are much more straightforward than solving every corner case with _FilletEdge.


BlendSrf command has AddShapes option. DevLoft command has Rulings option. I believe that the best way to deal with the failing fillets is adding Rulings option to the FilletEdge command. The Rulings will divide complex filleting task into several simple filleting tasks.

Yes, BlendSrf has AddShapes. I use it many, many times per day. That is why it would be nice to use an existing centralized curve to automatically AddShapes that are perpendicular. Even that will not handle all cases, but it would be a much improved starting point.

FilletEdge is good at a lot of things, but when it fails it fails on a complex corner. I’m not sure how rulings help there.

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