# Cannot join SubD objects

**URL:** <https://discourse.mcneel.com/t/cannot-join-subd-objects/163097>\
**Category:** SubD\
**Tags:** windows, rhino7\
**Created:** [July 21, 2023, 9:29am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097 "2023-07-21T09:29:38Z")\
**Posts on this page:** 14\
**Page:** 1

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**Author:** ![mark.alaksa](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mark.alaksa/32/484207_2.png) [@mark.alaksa](https://discourse.mcneel.com/u/mark.alaksa)\
**Post date:** [July 21, 2023, 9:29am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/1 "2023-07-21T09:29:38Z")

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Hi, Im working on 3D model in Rhino SubD and after latest update I cannot join 2 SubD objects. I used SubD Sweep One Rail command and I cannot join generated face (blue) with the rest of the model (green). There are no duplicated faces and I have checked mirroring settings.

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/8/b/4/8b47c5f77764d52d1cd1b405db562dba25366822.jpeg)

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**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [July 21, 2023, 9:44am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/2 "2023-07-21T09:44:27Z")

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nearly impossible to help without a file.  
did you try to  
\_stitch  
of both edges - instead of join ?  
(this might solve some imprecision)  
\_alignvertices , then \_join might also be an option

post the file to get more feedback.

kind regards -tom

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<div class="post-metadata">

**Author:** ![mark.alaksa](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mark.alaksa/32/484207_2.png) [@mark.alaksa](https://discourse.mcneel.com/u/mark.alaksa)\
**Post date:** [July 21, 2023, 10:19am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/3 "2023-07-21T10:19:25Z")

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Hi Tom,  
thanks for your feedback, “stitch” was not working at all. Please find the problem part in the attachment.

Best regards, Marek  
[SubD\_Join\_Problem.3dm](https://discourse.mcneel.com/uploads/short-url/ft7ROuz6XEyTzGbi2uPGc5cit2o.3dm) (298.5 KB)

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<div class="post-metadata">

**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [July 21, 2023, 10:29am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/4 "2023-07-21T10:29:59Z")

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the blue surface is a nurbs surface  
the green surface is a subd  
you can not combine those two different object-types

use  
**SubDSweep1**

and you can not join 3 subd edges together…

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<div class="post-metadata">

**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [July 21, 2023, 10:35am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/5 "2023-07-21T10:35:18Z")

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![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/0/f/0/0f00936aed648834372fadb9b40d233b74c15690.png)  
[SubD\_Join\_00\_tp.3dm](https://discourse.mcneel.com/uploads/short-url/jF3epCxxoVcAgBFgK9VT0rKLeSs.3dm) (3.4 MB)

delete the violett faces  
\_subDSweep1  
\_join

and please update / Edit the title / remove “BUG”

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<div class="post-metadata">

**Author:** ![martinsiegrist](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/martinsiegrist/32/772775_2.png) [@martinsiegrist](https://discourse.mcneel.com/u/martinsiegrist)\
**Post date:** [July 21, 2023, 10:40am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/6 "2023-07-21T10:40:26Z")

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I edited the title.

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<div class="post-metadata">

**Author:** ![mark.alaksa](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mark.alaksa/32/484207_2.png) [@mark.alaksa](https://discourse.mcneel.com/u/mark.alaksa)\
**Post date:** [July 21, 2023, 10:49am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/7 "2023-07-21T10:49:46Z")

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Now that is disturbing. That 3dm is export from original file, because I cant share the full model. And in Original file it is 1 open SubD and it was created with SubD Sweep. I know I cant combine different object types Im working with this every day. See the same selected face in original file. So it looks like Rhino is somehow tracking this SubD as Surface in original file, but I dont know why…

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/9/5/c/95cefdbbb5ea28ab567a1067c57b2cd71a13fcac.png)

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<div class="post-metadata">

**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [July 21, 2023, 11:42am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/8 "2023-07-21T11:42:25Z")

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> [@mark.alaksa](#):
>
> Now that is disturbing

> [@Tom\_P](#):
>
> delete the violett faces  
> \_subDSweep1  
> \_join

does this work for you ?

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<div class="post-metadata">

**Author:** ![mark.alaksa](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mark.alaksa/32/484207_2.png) [@mark.alaksa](https://discourse.mcneel.com/u/mark.alaksa)\
**Post date:** [July 21, 2023, 11:55am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/9 "2023-07-21T11:55:50Z")

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No, it is not… the original file was created like that and \_join command was not working and that is the main problem of this whole topic. As I wrote earlier (and also attached the screenshot of it), in original file all objects are SubD. But after export the “unjoinable” SubD face converted itself to Surface and in original file it is still SubD…

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<div class="post-metadata">

**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [July 21, 2023, 12:11pm UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/10 "2023-07-21T12:11:32Z")

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did you check the subd faces i marked violett above ?  
you may also try  
\_appendFace

Can you provide a sample file that allows to reproduce the error: a subD-Face that is exported as a Nurbs-Surface ?

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<div class="post-metadata">

**Author:** ![mark.alaksa](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mark.alaksa/32/484207_2.png) [@mark.alaksa](https://discourse.mcneel.com/u/mark.alaksa)\
**Post date:** [July 21, 2023, 12:46pm UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/11 "2023-07-21T12:46:21Z")

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The violett faces appierd after file export, but they are not in the original model. Yes, in the exported file \_join command worked after it was deleted. Maybe will have to recreate this model from scratch.

I cant, because everytime I export the problem part from original file, it will automatically convert the SubD face to the Surface

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<div class="post-metadata">

**Author:** ![Tom\_P](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/tom_p/32/766520_2.png) [@Tom\_P](https://discourse.mcneel.com/u/Tom_P)\
**Post date:** [July 21, 2023, 1:16pm UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/12 "2023-07-21T13:16:37Z")

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> [@mark.alaksa](#):
>
> I cant, because everytime I export the problem part from original file, it will automatically convert the SubD face to the Surface

upload the original file ?  
or do a copy of the file (save as…) and delete everything else ?  
I think it s nearly impossible to debugg an error, that can t be reproduced

contact **[tech@mcneel.com](mailto:tech@mcneel.com)** if the issue persist.  
if this is really a bug and the data is confidential.  
make sure to include your system info  
run the  
\_systemInfo command.  
and include a link to this topic

good luck, kind regards -tom

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<div class="post-metadata">

**Author:** ![pierrec](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/pierrec/32/772752_2.png) [@pierrec](https://discourse.mcneel.com/u/pierrec)\
**Post date:** [July 24, 2023, 4:36pm UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/13 "2023-07-24T16:36:47Z")

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@mark.alaksa It looks like you might be trying to create a non-manifold edge in your SubD (an edge that is connected to 3 or more faces). These are not fully supported in Rhino (and not well defined in the original SubD papers), and as such most SubD commands will prevent you from creating them.

Some of what you describe in this thread sounds like a Rhino command is creating bad geometry. That would be a bug that we want to fix.

Can you contact [tech@mcneel.com](mailto:tech@mcneel.com), or upload your file to [Rhino - Upload to Support](https://www.rhino3d.com/upload) with [pierre@mcneel.com](mailto:pierre@mcneel.com) as the destination email? We keep files uploaded this way private and do not share them outside the organization, if that is a concern.

Thanks,  
Pierre

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<div class="post-metadata">

**Author:** ![mark.alaksa](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/mark.alaksa/32/484207_2.png) [@mark.alaksa](https://discourse.mcneel.com/u/mark.alaksa)\
**Post date:** [July 25, 2023, 11:37am UTC](https://discourse.mcneel.com/t/cannot-join-subd-objects/163097/14 "2023-07-25T11:37:30Z")

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Hi Pierre,  
No, it is only edge to edge connection…I’ve already completely remodelled this object by simply snapping Single SubD Faces on the SubD vertex of the previous (original) object without any shape changes or removing SubD faces and it was possible to join faces that were previously unjoinable. I think that bug is hidden somewhere in the \_Reflect SubD Object command, and it happens after you change the “reflection” setting several times, like I did in previous model.