Offset only certain sides of a polygon

One thing that seems so easy to do but I fail to achieve this in an easy manner:
I want to offset a curve (not necessarily closed!), but not all sides, just some of them.
Is there really no way to do that?

In other news: it would be great if the offset command would respect subselection.

Hi Luc - SubCrv should let you do this. V7/Wip allows sub-object selection and this works with OffsetMultiple


Hey Pascal!
Thanks again for your quick answer!

Still on V6 here…
I fail to see how SubCrv helps… :thinking:
It just seems to shorten the whole curve in weird ways.

Hi Luc - if you have a polygon, start Offset and then run SubCrv - click on the polygon and snapping to the end points select one or more (contiguous) sides - these should be the ones that offset… ?



Wait, that works?
Doesn’t seem to be the case here :frowning:
If I run SubCrv it auto cancels the offset for me.

Hi Luc - if you run SubCrv from a button, if probably has a macro with

! _SubCrv

that is for making a subcrv. But, in V6 +, it is a nestable command, so you can type it or make a button with just


(no ‘!’) and that will not cancel the currently running command.


I typed it in, actually.
Even tried the " ’ " to no avail.

Hmmm - and you are calling SubCrv at the point where you are being prompted to select the curve?


I am doing exactly the same thing as you do in the video…
(Except it doesn’t work, ofc)

There must be something dumb and obvious that I am just forgetting… when you type SubCrv + Enter, what is the next prompt? V6, Windows, correct?


The prompt says “Select curve to shorten”
(On german. Might this be a culprit?)
Windows 10 with Rhino V6, true.

Hi Luc - that is the prompt I’d expect if running the ‘full’ command - nested, it should say ‘Select curve to temporarily shorten.’ Could be a localisation bug, maybe? Let me ask McEurope to have a try.


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By the way, @John_Brock, the thing I’d actually would like to see would be the following:
Getting a new curve, not just a part from it.

This is the expected results of offsetting using the subcrv tool Pascal mentioned.

I know! It’s more a wish for the future! :slight_smile:

Once it starts working, SubCrv can be used inside Connect as well, to make those odd sides.


Okay it’s getting really weird now:
(I hope you’re sitting well!)

There is the command “Teilkurve auswählen” (‘select sub curve’).
It can only be invoked by clicking on the button in the selection menu.
It calls _SubCrv.

However: I can’t call “Teilkurve auswählen” via the CLI.
Only KurveKürzen (‘shorten curve’). Which calls also _SubCrv.

So I can’t call the selection command when inside of another command.
However!: I can call previous used commands. (it’s on my middle mouse button).
There it actually differs between “Teilkurve auswählen” and “Kurve Kürzen”. (Even tho both actually are the same command!)
If I then use the “Teilkurve auswählen” command it works like in your video.
Otherwise it won’t.

What a strange bug, huh!? :smiley:

Hi Luc- maybe this is what you did previously but just in case, what happens if you type in "_SubCrv ", like that, in English with the underbar in front, does that work nested (I assume so…)


Huh. Weird. I did so the whole time, and it didn’t work.
Restarted Rhino just now to see if it makes any difference – it suddenly worked.
The hell? :man_shrugging:

Thanks for your help!