Problem when using fillet commands - "Failure in building corners"

Hi there, I’m rather new to rhino. I have come across several issues I haven’t been able to solve while trying to fillet my polysurface as seen below. Using FilletEdge the error “Failure in building corners” pops up when I try using it on this edge. When using FilletSrf the error “Failed to “split” first surface” pops up. The edge on the opposite side of the polysurface has the same errors.

Let me know if there is a different command or series of commands that I should use that would work better.

Here is the Rhino File.

Fillet Problem.3dm (10.5 MB)

Thanks in Advance

Hi Neil - those faces come tangent, or very nearly, to one another there at the corner - the complex face to the right has its edges tangent to each other at the point.


Where untrimmed adjacent edges are tangent, the surface normal is undefined and offseting fails - ofsetting is a part of filleting, behind the scenes, and I guess this is where it is all falling apart. It may be tricky anyway with the scooped out face coming tangent to the bottom face but let’s fix the one thing first - I’d make it like so -

wher the edge is trimmed off of a more rectangular surface rather than having the surface UVs coming to a point


The problem is you have created a degenerate surface that will cause many commands to fail. Here is a file showing how to make the surface so that it is not a bad object.
FilletProblemx.3dm (259.3 KB)

Thanks Pascal.

Makes a lot more sense now. What commands/procedure did you use to create that rectangular surface exactly? Sorry creating surfaces are still a little new to me.

Also unrelated to this topic but I have another project I’m working on that looks like the above image. How would you create the missing surfaces for it? I have tried every command / variation that I know and I cant get the surface that I want with any of them. It always has a seam in the middle of the surface as seen below. The surface that I’m trying to get is a smooth curve from the left side to the right without a seam in middle, hope that makes sense.

Here is the Rhino file if you would like to tinker with it.

Surface.3dm (3.5 MB)

Thanks again

Hi Neil - I’d over-build all that


and then trim it all back at the intersections:

(rather than start with guesses of the intersections and working backwards to the surfaces.)


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