2 Rail sweep bug?

rail error dif.3dm (1002.8 KB)
This may be a bug or maybe it’s just me! 2 rail sweep with chain keeps failing here but can’t see why. surfaces on the chained edge (?) are tangent, as far as I can see. This has no great priority, though it is annoying. Win 10 64bit, Rhino 6.11 vanilla.

@Tone - Try again using the “Rebuild…” or “Refit…” cross section options.

Hi Tone - for what it is worth, I’d make that corner something like so:

rail error_PG.3dm (326.7 KB)


Hello Pascal
Yeah, I wasn’t really expecting it to be the result I was looking for, I was just surprised it didn’t work.

In my opinion, Pascal’s approach is the best way to solve this area. I played a few minutes with his file to make both extra surfaces smoother. First, I used “Scale 1D” to make the upper area of the split surface more pronounced, then I re-trimmed it and applied “Match surface” to the 2nd surface. Then I turned on the “Zebra” and adjusted the control points of the 2nd surface manually with the UVN tool to further enhance it.

I’m also curious why the “Sweep 2 rail” command failed to build a surface with the “do not change cross sections” option. As Vanessa Steeg noted, the “Refit cross sections within” seems to work, though it’s an approximation with user set tolerance and may add extra control points.

rail error_PG_extra_UVN.3dm (5.2 MB)