What is making filletEdge not work for entire edge?

I am trying to create a fillet between two surfaces. I thought it would take 10 seconds, but I was very wrong.

As should be evident from the screen shots, the fillet works as desired on left side, but it fails on the right side.

On the right side of the screen shot, the fillet continues straight through an area where there is no edge. And there is a second fillet that is not continuous.

It doesn’t seem to matter how I select the edges, or what setting I use within the FilletEdge command. (I’ve tried all of them a couple times…) In the example I used “face edges” option to select edges, and selected the flat perimeter/flange.

The “bump outs” on this surface were both drawn using the same technique. They should be exactly the same. But clearly the program is treating them differently.

Please, can anyone explain why this happens? How to fix it? How to avoid it?

I keep running into this problem. I have drawn and re-drawn this object several times, testing different methods and order of operations. Getting the raised surfaces to transition smoothly was a challenge, the main challenge being the fillet command. I finally got that detail drawn in a way that the fillet command liked, but now the fillet command fails again on the very next step!

If I choose not to buy this program, it will be 100% because of the fillet command… Unless someone can explain what the root problem is and how to work around it?

Please assign your new messages to the appropriate category so the right people see it.


Hello - it looks like, and it is hard to say without a file, the fillet radius you are adding is as large or larger than the existing vertical fillets. If you are making colliding fillets either do the largest ones first or select the edges at the same time.

Runs out of room here:



Thanks Pascal. The existing fillet was 3mm, and the new fillet is also 3mm.

Based on your suggestion I tried again experimenting with different fillet sizes, and it worked just fine with a 1mm fillet. As the fillet got larger, there were progressively more “deviations” from my desired result.

As a newb, in cases like this where an obviously wrong fillet is created, I would prefer the fillet not be created at all. Other commands give an explanation for why they failed on the command line, which has been helpful. I have had cases where the fillet seemed ok at first, but later I discovered defects that required undoing everything I did after the fillet command.

I will try re-drawing these features without the fillets, and then fillet everything in a single operation.

Tom, I see you retracted your comment, but I would welcome any suggestions you or others may have on simplifying the model. (I kind of wish I could just hand out the file to get help and suggestions, but the project is important enough to me to not want to put it out there like that.)

I spent an ungodly amount of time with this surface getting to where it is! As far as I can tell it is now almost perfect according to the surface analysis tools. I admit there are a ton of curves, but generally speaking if I remove any of those curves or simplify the surface, the resulting surface is altered. I did it to control the shape. Controlling the shape is critical for my project.

The surface transitions between specific shapes, and Rhino doesn’t seem to respect my desire to preserve those shapes. For example, the top of several curves in the middle needs to be perfectly flat, and then they smoothly transition to a domed surface on one end. Rhino keeps trying to turn the flat center section into a “W”. Adding more curves helps keep it under control, and creating the surface with more control points also helps.

If you really want full control over your fillets, learn to use FilletSrf.