FilletEdge refuses edge associated to faces with small diedral angle

FilletEdge will not allow selection of edges associated to faces with small dihedral angle, whatever radius is input for the fillet :

FilletEdge fails on small diedral angle.3dm (116.6 KB)

I managed to select the edge in question and to make a fillet, but strangely that was after adding another face to the polysurface.

Now I need to make a fillet with this new face, but the dihedral angle is even smaller, and I just can’t select the edge again…

Miracle on one edge-Not the other.3dm (93.9 KB)

Well, the one that doesn’t work has an dihedral angle of less than 1°, and your angle tolerance is 1° - so Rhino considers them “tangent”… (I would suggest working with a default of 0.1° for angle tolerance, the default of 1° is far too large)

However, that is not all that is going on, FilletEdge must have some hard-coded internal cutoffs somewhere. I tried with FilletSrf, and whether or not the fillet is created depends also on the file absolute tolerance - I think in order to avoid creating extremely skinny surfaces… (my theory at least). So I was able to get FilletSrf to work by lowering the file tolerance. The more I lowered it, the smaller radius it would accept to make the fillet… So there is some internal checking going on… @chuck?


Yes, but in my first file, the dihedral angle is more than 1°, and I could not select the edge.
It was only after adding another face that I could select it.

I measured it as 0.72° approximately… But yes, there is something else going on besides that.

You are right.

Looks like the test uses the default angle tolerance of 1 degree. I’ll make a youtrack to see if it can be changed to use the file’s angle tolerance.

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