Variable fillet of a corner Joining 3 sides

Hey there!

I was wondering if anyone knew a way to create a rounded corner(where three surfaces meet) that tapers out into a variable fillet which ends at 0.00.

I’d like the corner to be rounded by 7/8th" and then gradually taper to the clean edges of a 0" fillet on each of the edges that the three corners meet the others.

Here’s a picture of the corner before whatever this is I am trying to do:

And here is the closest I could get. It’s really awkward:

Let me know if you have any ideas!

I’m working on a mac OSX with version 5.3.2.

Thanks for your help!


Hi Keith - on a cube, that surface is a sphere, centered .875 inward from each face of the box, with a radius to the end points of one of the arcs…


Hey Pascal,

Thanks for the speedy response!

Was able to do what you said and got to the point where your picture shows (thanks for that btw!)

But after using the trim function to cut off the corner and attach the sliver of the spher eto create the fillet I got this:

And then further trimmed:

Unfortunately, this does not give the filleted or blended quality I was looking for. You can see there is still a harsh edge.
You can see it better from the side view.

Basically the new “corner surface” doesn’t blend seamlessly into the surrounding 3.

How can I incorporate that?


Ah, sorry… I misunderstood the request. That is less straightforward…
@Keith_H - a construction something like in my attached file may be somewhat-ok-ish. I can’t help but think that is not the best way to do this though - I’ll see if I can get something better, unless someone else comes up with it…
Softened corner.3dm (113.9 KB)


Oh no now you’ve got me worried!


That’s the closest that I’ve seen! Thank you for putting that together!

OK - it is a variable fillet (VariableFilletSrf) between the original sphere surface and the planes - these are set to zero at the ends, and a handle added at some fraction of the original arc radius (about a fifth, say) in the middle. You only need to make one of these, arrayPolar - note the custom CPlane in my file - and then trim with radial lines or vertical planes from that same plane.

(Also, you can make one of these carefully and then just bring it in and position it on any corners that want this type of transition at this scale - no need to build it every time - scale from the box corner point once in position to get different sizes…)


Thanks Pascal much appreciated!