# Su RH si su GH no, perché? #sweep2

**URL:** <https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244>\
**Category:** Grasshopper\
**Created:** [January 28, 2021, 10:28am UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244 "2021-01-28T10:28:59Z")\
**Posts on this page:** 15\
**Page:** 1

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**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 10:28am UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/1 "2021-01-28T10:28:59Z")

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This happens: I build a definition and at some point I need to do a two-track sweep. I have all the elements I need but the sweep behaves strangely. I bake the rails and the section and on Rhino the sweep works perfectly.

Because?  
Succede questo: costruisco una definizione e ad un certo punto ho bisogno di fare uno sweep a due binari. Ho tutti gli elementi che mi servono ma lo sweep si comporta in modo strano. Faccio il bake dei binari e della sezione e su Rhino lo sweep funziona perfettamente.

Perché?

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/e/2/6/e26f10393a15482c00ac0fb4be552567445eea6c.png)  
[sweep2.gh](https://discourse.mcneel.com/uploads/short-url/nRDdxqZ50B0y7JTBOqGF1iqq7lc.gh) (77.3 KB)

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**Author:** ![laurent\_delrieu](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/laurent_delrieu/32/601605_2.png) [@laurent\_delrieu](https://discourse.mcneel.com/u/laurent_delrieu)\
**Post date:** [January 28, 2021, 10:35am UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/2 "2021-01-28T10:35:32Z")

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If you are Italian, there is an Italian Discourse

> **[McNeel Forum](https://it.discourse.mcneel.com)**
>
> Discussions about McNeel related software products (Rhino3D, Grasshopper, Flamingo, Bongo, Brazil, Neon)

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**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 10:37am UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/3 "2021-01-28T10:37:51Z")

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that’s better?

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**Author:** ![DavidRutten](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/davidrutten/32/755688_2.png) [@DavidRutten](https://discourse.mcneel.com/u/DavidRutten)\
**Post date:** [January 28, 2021, 12:17pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/4 "2021-01-28T12:17:35Z")

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Looks okay in GH+Rhino7. Are you doing this on Rhino6?

 ![sweep](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/5/e/8/5e8c6d82e3374749313e4bccc730f66bb11d5961.jpeg)

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**Author:** ![Joseph\_Oster](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/joseph_oster/32/549124_2.png) [@Joseph\_Oster](https://discourse.mcneel.com/u/Joseph_Oster)\
**Post date:** [January 28, 2021, 12:28pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/5 "2021-01-28T12:28:31Z")

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I don’t know why Sweep 2 fails _(in R6)_ but you can get the same result by using Pull Curve before Surface Split and then lofting the original and offset surfaces.

 ![sweep2_2021Jan28a](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/e/9/6/e96f59fd62bcdc3dac9e175e2f08b2b00b7d8103.png)  
[sweep2\_2021Jan28a.gh](https://discourse.mcneel.com/uploads/short-url/akR4e8d6t12u7SJyv5DfDLeLCp1.gh) (78.5 KB)

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**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 4:34pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/6 "2021-01-28T16:34:49Z")

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Yes Rh6

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**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 4:35pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/7 "2021-01-28T16:35:25Z")

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Thank’s a lot Joseph I try immediately

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**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 4:49pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/8 "2021-01-28T16:49:34Z")

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to simplify: I have two track curves and one section. The sweep command does not work in any case  
[sweep-dosent-work.gh](https://discourse.mcneel.com/uploads/short-url/o48JxZ2kVbbhLxOHNrNNeCsExbE.gh) (85.6 KB)

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/6/5/8/658221875f5fd527a9d93f3d54cb779fec400f54.png)

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<div class="post-metadata">

**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 4:51pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/9 "2021-01-28T16:51:20Z")

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Sorry Joseph I must necessarily use sweeps and not lofts for a demonstration.

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**Author:** ![Joseph\_Oster](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/joseph_oster/32/549124_2.png) [@Joseph\_Oster](https://discourse.mcneel.com/u/Joseph_Oster)\
**Post date:** [January 28, 2021, 5:09pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/10 "2021-01-28T17:09:54Z")

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> [@Carmen\_Russo](#):
>
> Sorry Joseph I must necessarily use sweeps and not lofts for a demonstration.

You have demonstrated that Sweep 2 can fail when Loft works. 😉

Interesting to note though that Loft also fails without using Pull Curve before Surface Split.

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<div class="post-metadata">

**Author:** ![Carmen\_Russo](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/carmen_russo/32/500620_2.png) [@Carmen\_Russo](https://discourse.mcneel.com/u/Carmen_Russo)\
**Post date:** [January 28, 2021, 5:47pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/11 "2021-01-28T17:47:51Z")

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in Rhino7 sweep is working 🙂

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/7/2/6/726e784c2ff74294975883efaee8e9bf042d1d8a.png)

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**Author:** ![anon39580149](https://avatars.discourse-cdn.com/v4/letter/a/977dab/32.png) [@anon39580149](https://discourse.mcneel.com/u/anon39580149)\
**Post date:** [January 28, 2021, 5:53pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/12 "2021-01-28T17:53:10Z")

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Use Fit Curve or Loft

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/5/6/1/561e11aa2fe3f723129a06f2f32c466f8a8bc9d1.jpeg)

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**Author:** ![maje90](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/maje90/32/762888_2.png) [@maje90](https://discourse.mcneel.com/u/maje90)\
**Post date:** [January 29, 2021, 12:51am UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/13 "2021-01-29T00:51:21Z")

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Ciao Carmen.  
Il tuo è un problema particolare, e in generale la funzione sweep è tra le più ingannevoli da usare. È meno “assistita” che la controparte su rhino.  
Quello che hai riscontrato te lo defenirei sostanzialmente un bug. In altre situazioni dovrebbe andare bene come avevi fatto tu: tieni la sezione vicino a dove

In questo caso, reparametrizza le due rotaie per risolvere:

![2021-01-29 01_34_32-Window](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/3/8/a/38ad6f454e3db09e3cdd3ba9568cc5bf1b831d71.png)

Particular problem, generally sweep function is one of the most tricky to use. It is less aided than rhino counterpart.  
I’d say this is a bug. In other situations it should be fine how it was used.

Reparametrizing the curves fix the problem.

Still it’s strange, the section curve is generated right on the seam of the rails, but it behaves like the seam was actually on the only other “discontinuity point” (G0) on the rails…

Edit: actually @Gambler found this solution 11hours ago in the italian forum.

* * *

I’m italian but i never visit the italian forum. The home page there… each scroll is a week 😅 … can’t really blame someone trying his luck here instead.  
Guys, if you think it’s useful feel free to tag me…

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**Author:** ![ShynnSup](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/shynnsup/32/767220_2.png) [@ShynnSup](https://discourse.mcneel.com/u/ShynnSup)\
**Post date:** [January 29, 2021, 5:57am UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/14 "2021-01-29T05:57:36Z")

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Do you mean Italians talk too much or did I misunderstood? Anyways this is interesting. I am not even Italian but I have checked that discourse one or two times. Whole new worlds out there 😁

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**Author:** ![maje90](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/maje90/32/762888_2.png) [@maje90](https://discourse.mcneel.com/u/maje90)\
**Post date:** [January 29, 2021, 2:31pm UTC](https://discourse.mcneel.com/t/su-rh-si-su-gh-no-perche-sweep2/117244/15 "2021-01-29T14:31:59Z")

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No… with “each scroll is a week” i meant the quantity of content.  
With 4 scrolls i can see 2020’s posts.

On this english discourse with 4 scrolls i’m back at 8 hours ago.

> [@ShynnSup](#):
>
> Italians talk too much

maybe you can apply that on me 🙈 😂