Scratch on unfolded cylinder


I use the following formula to unfold a cylinder

The cylinder is unfolded but the rendering is not good

Do you have any idea what could be the reason ?

Best regards,

Hello @Marvin !

At a first glance, I would say that there is several elements at the same position.

Could you please share your data?


Bonjour Francois,

Thank you for your answer.

I think you are right because the problem don’t appear if I “clip” the cylinder. In this case, one part is OK but not the other one.

Clipping :

Part OK :

Part NOK :

I will prepare the data to send.

Thank you

Hi !

Here is the link to download the mesh : model

Thank you in advance.

Looks like you have unconnected elements inside your volume. It maybe the root of the issue.

If I apply extract suface filter, then clip to see inside, I can see internal surfaces (I’ve added a slice with bold lines to emphasize the issue):

Could you please share your pipeline ?


This part is the inlet part of an axial fan. Just after this part, you have the rotating part then an outlet zone with a “rectifier” (not sure regarding the translation).

The same issue appear on the 3 parts.

May be we see on your picture the differents areas from the decomposition ?

Best regards,

The transformation looks good but the issue is that the cells are still connected (topology is preserved). It means that there are cells between the two sides of the unfolded cylinder.

One solution is to use two clip filters (one is inverted) to “cut” the cylinder, then apply the transformation with the calculator:

I’ve added a small offset on Y (+/-0.0001) to avoid numerical errors.

Here the associated ParaView state: (9.1 KB)

Hope this helps!

Best Regards,

Bonjour François,

Thank you very much, it works !

Best regards,

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