Can someone please explain why Fillet Edge is failing?


I have been going through hell will this function.
Why isn’t it working???

I have drawn a simple letter T, I extruded it 3mm, and I’m just trying to make a 0.45mm fillet, but even 0.3mm fails.

I beg someone to tell me: what is wrong with my curve? What should I be doing?

I attach a file if someone is kind enough to have a look.
The first T is the curve as I drew it.
The second T below was rebuilt, and still fails.
Fillet problem WTF.3dm (1.0 MB)

Thanks in advance

Hi Rhino22 - the corners are too small in radius to accommodate the fillet you are adding- it looks like the corners have a minimum radius of about .12 or so, so for a constant radius fillet you’ll need to set the radius smaller than that - You’ll see on your example then even where it does not go crazy on some of the corners, the fillet collides with itself and overlaps itself in ugly ways.


Hi Pascal and thanks

Is there a way to analyze the smallest radius without having to run the radius tool all around the edge?


If you look on the file here, there is an “e” with an eye that has a 0.025 radius, yet I can fillet it at 0.1
Why is that?

Thanksfillet e.3dm (297.2 KB)

Well, if the corner is an inside one, then the fillet can ‘splay’ out radially around it - there is no collision as there is on outside corners.

One way to locate potential problem corners is to turn on CurvatureGraph for the duplicated edge curves or the original text curves in this case- measure the location with the tallest graph. (= highest curvature/smallest radius)


Yes it’s an inside edge so the angle is open, I realized that this morning.
I get it now, still I think that the function is so essential that McNeel should really improve it.

Thanks for your help