Rounding a complex object

Doing this as a test. I have created a very amorphic object and went to round it and only the top would round. Yep it is a twist split in the middle with a curved top. I want all of the edges to be equally rounded as the top is. Any advice? Thanks!

Wonder if pipe, explode pipe, extend pipe, split ,then2 rail sweep and finish corners manually

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What a great question. Fillets can be a real challenge. What works on one edge might fail on something that seems similar. In your example, the angle between the top and sides is different than the sides to each other, and that alone might account for the top filleting and the rest not.

The thing to check out would be the Rail Type. There are three options, and you can get compellingly different results from each.

The default is RollingBall, which you can think of as dipping a sphere in ink, and then “rolling” it along the inside corner, and where the inky ball leaves a mark, the surface is split and trimmed there, and a new surface, with the same radius as the inky ball, is created and joined between the two trimmed surfaces.

The other two options are DistFromEdge and DistBetweenRails. A compelling example of the difference between all three options is if you make three angled edges - one acute angle, one right angle and one obtuse angle, and apply each Rail Type to each of the three angles. Sometimes, some of the fillets will be similar, and other times they will be quite different. Chamfer uses the same methodology, but we tend to model with fillets much more than chamfers.

fillet options.3dm (177.1 KB)

If you still can’t get the fillet to work, there are a number of manual work-arounds that are essentially doing something very similar. Pipe, split, etc was mentioned above. DupEdge, OffsetCrvSrf, Split, draw some sort of radius then Sweep2, or maybe Loft between the split edges on the surfaces and the duped edge from the original corner. One way I’ve drawn a new radius is to project a curve on to both surfaces, after the corner has been trimmed away, then Blend Curve between the projected curves, and use the blended curve segment to sweep. Lots of ways to do this manually…

Another consideration is if you will want several edges that intersect to all be filleted, try and get them all to go at once. Doing it piecemeal can be more of a challenge, but there are numerous video clips showing just that.

Best regards,

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Hello- please post a file with the object to fillet- someone will have a crack at it.


The easiest way might be to fillet the vertical edges with a larger value and fillet the horizontal edges with a smaller value? But I’d probably do it in the same way as Markin.

  • Duplicate the outer edges before you fillet. Pipe and then split the surfaces.
  • Blend the edges marked 1. and then split the edge of the top surface perpendicular to the radii of the blended vertical edges.
  • Blend curves on the top face (marked 2.) where you’d split them so it creates a nice rounded corner on that top face. Trim the corner of the top face leaving you with rounded corners.
  • Extract Isocurve for both the top and vertical faces (Do this a couple of times around the object) blend curve with tangent and then two rail sweep.

Thanks guys. It worked by duplicating the edges and making a pipe and cutting that out. Then blend curves. I used a network surface to create the corners. Just a little rusty.

FilletEdge should work - can you post the object, pre-filleting?



One half of it

Thanks - I think this will cause problems for any but the tiniest fillet radius:


Good catch, thanks!