# Trouble with Loft

**URL:** <https://discourse.mcneel.com/t/trouble-with-loft/146493>\
**Category:** Grasshopper\
**Tags:** windows, mac\
**Created:** [August 14, 2022, 2:08pm UTC](https://discourse.mcneel.com/t/trouble-with-loft/146493 "2022-08-14T14:08:43Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Pierrafee](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/pierrafee/32/486023_2.png) [@Pierrafee](https://discourse.mcneel.com/u/Pierrafee)\
**Post date:** [August 14, 2022, 2:08pm UTC](https://discourse.mcneel.com/t/trouble-with-loft/146493/1 "2022-08-14T14:08:43Z")

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Hi,  
I try to loft 2 surfaces (one is from Patch, other is from Curve Network) with grasshopper. This is doesn’t work, and return no error. I think the problem is my upper surface, but I can’t fix it!  
Here is the files, if someone can explain me 🙂  
Thanks  
[Loft problem.3dm](https://discourse.mcneel.com/uploads/short-url/2EBVLKuZZ7zRWFWya09BQrDonz0.3dm) (3.0 MB)  
[Loft problem.gh](https://discourse.mcneel.com/uploads/short-url/68boDQddNJ747Jm5G7Pa9GDWJvi.gh) (1.9 KB)

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<div class="post-metadata">

**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:** [August 14, 2022, 2:21pm UTC](https://discourse.mcneel.com/t/trouble-with-loft/146493/2 "2022-08-14T14:21:01Z")

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Hello  
you must look at your inputs.  
 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/5/1/c/51c57d5e7971f8c0b8d8f238d68a06b4d1bfc8d4.png)  
For loft curve must be on a list. Here there are on two branches of a tree. Each one has just one curve. So you are asking make a loft with one curve. There must be some warning for that, but it outputs “null” instead !  
So flatten inputs and add option of loft

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/d/5/c/d5ce171e4fc1f54c356f9ab37c0aff01a99865af.jpeg)

 ![image](https://global.discourse-cdn.com/mcneel/uploads/default/original/4X/f/f/c/ffc3b650cdb30314bea37e339091a0e7ae0c14e2.png)

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<div class="post-metadata">

**Author:** ![Pierrafee](https://sea3.discourse-cdn.com/mcneel/user_avatar/discourse.mcneel.com/pierrafee/32/486023_2.png) [@Pierrafee](https://discourse.mcneel.com/u/Pierrafee)\
**Post date:** [August 14, 2022, 2:43pm UTC](https://discourse.mcneel.com/t/trouble-with-loft/146493/3 "2022-08-14T14:43:40Z")

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Thanks a lot for theses informations…! It works better 🙂  
I have to learn more about theses options: Flatten, Graft, Simplify, Reverse, Principal… it’s vague for me.