[Bug] Offset creates additional curve segments?

Serengeti (Rhino WIP)
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1

In the WIP, I encountered something strange: when I offset a particular curve and explode it, it creates additional segments in Grasshopper.

And it also does so in Rhino:

Note that this only happens in the WIP (9.0.25084.12305, 2025-03-25), Rhino 8 is unaffected.
Offset bug.3dm (64.1 KB)
Offset bug.gh (9.0 KB)

3

Hi, sorry about that. It was a regression I introduced when working on open curve trimming in Rhino 9. I opened RH-87019 to get this resolved.

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Components that trigger recompute after layer visibility change?
4

@Joshua_Kennedy I found another case where this happens:

image
image1756×1596 106 KB

If I offset the curve in question to a smaller distance with a relatively high tolerance, it also adds a segment. When I offset the curve further, the result is as expected.


Offset adds segment.3dm (66.3 KB)

5

@Joshua_Kennedy have you been able to get to this yet? I’m seeing the additional segments in offsets still.

Offset extra vertices bug.gh (9.7 KB)

6

In YT, you can follow the status of the bug:

image

State open means that the bug is not yet resolved.

7

The main problem right now is that Simplify curve is not able to easily get rid of these additional sections. So for anyone having issues do to the bug, here’s a workaround. You can separately filter out polylines from other multi-segmented curves and do this:

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image3157×696 261 KB

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8

This issue now seems to have made its way to Rhino 8 now as well. Version 8 SR25 (8.25.25308.13001, 2025-11-04)

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image1541×1281 44.5 KB

Offset Adds segments.3dm (38.9 KB)
Offset Adds segments.gh (12.0 KB)

9

Not quite. I only ever made it merge these segments if the segment it connects to was also linear. I can see why it’d be nice to have it do a linear extension of the curve instead of adding a new line segment there.

10

You are right, the issue is slightly different and does not emerge in closed polylines.

Does it though? If I extend the white curve in the file I posted above by 140 meters, I get this:

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image762×751 40.2 KB

This was a part of a polyline, meaning it is a linear extension so the lines could have been merged back into the main 2 segment polyline (which excludes the Nurbs Curve).
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image1920×910 137 KB

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image1920×939 137 KB

image
image1920×1100 157 KB

11

I should have been a little more specific. Only if both segments before and after the kink are lines. That’s probably more strict than it needs to be. I definitely think there’s utility in what you’re asking for. This request to me feels a lot like adding an extend option for a corner like is requested in RH-5176 (and several other issues over the years).

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12

You can sign me up for a smooth extension that you’ve mentioned in the YouTrack :wink:

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