# Creation of a centerline of an existing surface

Hello dear Grasshopper community,

I’m new to using Grasshopper.
Is it possible to create a middle line from a certain surface? In the photo, it is explained more understandable.

Greatings Alex

Welcome @alexander.naljot,

Since you seem to be dealing with a curved cylinder with a constant radius, you can get the middle curve like this:

Please note though that this won’t work for geometries other than cylinders!

The next time, don’t forget to provide a definition (GH file), since it facilitates providing help and is even kind of mandatory in this forum to get assistance!
I also invite you to read up on how to ask effective questions here.

cylinder_middle_line.gh (13.0 KB)

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Hello P1r4t3b0y,

Thank you for your help. I tried the Grasshoper Skrpt, but somehow he does not work on my suface, maybe you can look at this attached file. The surfaces are cylinders.
Thank you also for the advice on how to make a good post in this Grasshopper forum, as I said I am new to Grasshopper and learn something new every day.

Yours sincerely

Alex

Test bewehrung.3dm (388.2 KB)

Hello Dowazura,

Thanks for the help, I’ve tried your grasshopper script. The center line is not created in the correct position in the photo it is better to explain.

Yours sincerely

Alex

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What does this mean?

The problem is that your cylinders are topologically a little different than mine was in the above example. I hope you see now, why it is important to provide a file!
My cylinder had an interior edge, the seam line, and two naked edges, circles at both ends. Your cylinders have the required seam edge, but four naked edges instead of two simple circles. Joining the curves pairwise to form two closed curves/circles remedies the problem!

cylinder_middle_line2.gh (14.8 KB)

Also, if you want other users to be notified, when you write a reply, you have to use the reply function under the concerned comment, quote something from their post, or tag them by username, otherwise they won’t see your post.

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Great Thank you for your help.