Another fillet problem

I’m new to Rhino, and am having an an issue trying to fillet an edge on a solid I created with NetworkSrf. It almost works, but there’s a knot in the offending edge that seems to mess it up. Seems like maybe it has to do with the directionality of the surface? The object is a valid polysurface and I the radius shouldn’t be too big… Any pointers would be much appreciated!

The selected edge (requires selecting on both sides of the knot):

The resulting fillet:

There are two things that come to mind looking at the screenshots. First, the radius may be too large given the geometry it’s meant to travel around. Second, the singularity at the tip in the networksrf is a zero dimension side to that surface. I find trimming these out can help reduce fillet issues. Post the file if you don’t have any luck with these suggestions and I can take a look as well.

Thanks Brian! I don’t think the radius is too large for the given geometry, but I might just not understand that. It seems more likely to me that the latter is the problem… I’m not sure exactly how to trim out the singularity though. Do you mean just trimming off the end so that it becomes a flat? I can’t quite picture how to do this without compromising the smooth curve.

I’m attaching the file — my goal is to put a 1/8" round on all of the edges which are currently sharp, including the flat on the bottom and the two cut out sections.

Fillet Problems.3dm (206.4 KB)

Hi Wlabs - FIlletEdge works at .1 or maybe a little larger, but fails - makes a mess - at .15. The radius of the surface is too tight to accomodate that large a fillet at the roundy ends. You can of course make a variable radius fillet by using AddHandle to add some control (i.e. smaller radius) going around those corners.


Thanks Pascal — I tried at 0.0625 (1/16 inch), doesn’t seem to do any better. The artifacts aren’t as grotesque, but still not a clean fillet. I did initially do a variable radius fillet just to see if it would work, and seemed like I needed to go all the way to 0 radius at the two singularity points.

Hi wlabs,

Regarding the bottom edge it is possible to have an approximate solution with a 1/8" fillet radius - I have attached a file. Basically I extracted the large curved surface and trimmed it with a plane offset by 1/8" (to remove the singularities), then rebuilt the missing part using Sweep2Rails - with two split edges for the short sides.

At that point FilletEdge works with the RailType se to DistFromEdge. There are still two tiny naked edges that can be removed by extracting and rebuilding the planars surfaces.

For the other cutout sections the 1/8" radius seems really too big, but hopefully this gives you a partial solution or a possible direction.

2015-11-03 - Fillet Problems.3dm (365.1 KB)

Cool, thanks for the suggestion Marco, very helpful. This actually will probably work for me… I can deal with a 1/16" round on the inner cut out portions of the solid, which seems to work fine.