Concave fillet or reverse fillet


is there a way or command to fillet a curve or surface like this,
parts at the right is what I want

Now I do it with a macro but a simple command like fillet would be great.


I don’t think there is a command for that. A simple solution to your problem is select the edges and run the pipe command and then boolean subtract the pipe from your object.

Do a ‘normal’ fillet, and then mirror the fillet curve using the ends as axis?

Prolly quickest in plain Rhino to make a bunch of circles on the corners to be filleted and then CurveBoolean.


Also, for solids, testInverseFilletEdge