Rhino is driving me crazy. I created all the lines in the attached drawing using Offset (they’re all degree-1 curves). When I export to AutoCAD, most of them are detected as parallel, but not all. Something seems wrong. are these lines parallel or not.3dm (3.3 MB)

@ar00302 , This is the same issue I found last night: the right hand blue line stops a microscopic distance short of the offset line and when connecting the two, the intersection is pulled to that end point. If I extend the blue line so that it reaches the offset line then connecting leaves the int…

[image] Ar00302: I tried something in your file, but I’m unsure if what I’m seeing is caused by a reporting bug There are two separate bugs that your video shows, One is that the angle between the two lines immediately after doing the offset is .00000085 degrees instead of the correct .000…

[image] Ar00302: Wasn’t it clear in my video Hi, I didn’t have time to study your video initially. However I have taken a look with the benefit of @jim ’s helpful summary and I can reproduce the issue. However as I don’t have a copy of your lines before you ran the chamfers you probably should…

@jeremy5 Please try this file — the error is reproducible instantly. Rhino fails to create parallel lines, and I have no workaround. Should I open a new post? This looks like a critical bug. I only discovered it by luck, and I’m worried it might be happening far more often, leading to serious downst…

Thank you for your time. This solves the problem. That’s why I solved the problem in the north wall by extending and trimming. I had the same issue there as well. Now I have to check everything, and I don’t even want to think about how many models might be affected. At least now I know how to fix it…

After correcting that issue, I can’t find 0.00000085 anywhere in the document anymore. Everywhere it now shows 0.00000000. Is this something we should take into consideration?

[image] Ar00302: But we should make another post about a critical Rhino bug: the Connect and Chamfer commands are modifying geometry orientation [image] Ar00302: I’ll open another post about the Chamfer and Connect issue. FWIW, if you use the blue line to trim the offset line at both e…

[image] Ar00302: Is this something we should take into consideration? An angle of 0.00000085 degrees is equivalent to an offset of 0.0148mm in a distance of 1km. I believe that the curvature of the earth dwarfs that at 8cm. I’m not going to lose sleep over it.

[image] Jeremy: An angle of 0.00000085 degrees is equivalent to an offset of 0.0148mm in a distance of 1km. So what?? It is still a wrong answer. The analysis tools are supposed to give correct measurements so that users can work with confidence that there work is accurate. When the user of…

[image] jim: it reported an angle of .000000085. That’s a bug in the angle command Thanks @jim RH-90680 angle reading depends on base angle

Also: RH-90681 Join breaks squareness

Is Rhino Breaking My Geometry? Offset Lines Fail Parallel

Rhino

brian (Brian Gillespie) December 9, 2025, 11:51pm 33

RH-90680 is fixed in Rhino WIP

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Is Rhino Breaking My Geometry? Offset Lines Fail Parallel

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