Isotrim is making extra surfaces that weren't there

Hi there,

I am having a problem with isotrim which creates more surfaces after plugging in a brep.

I have four lofts where I tried to get the exterior surfaces by using solid difference and isolating surfaces by using deconstruct brep.
When I plug my exterior surface brep into isotrim, it creates additional surfaces inside that are not originally there. Does anyone know how could I get rid of these surfaces?

The pink circle groups are where the issue is.


Hello sailor!

This is a recurrent issue in the forum, you might want to perform a quick search before posting next time.

Here’s the solution I came up with:
The main workarround is that you have to rebuild your surface, because Isotrim cannot operate with Trimmed Surfaces.


If this solves your problem, please mark the reply as solution.

Best regards,
Sir Ernest Shackleton

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Hi Shackleton!

I’m not too sure what happened because it turned out like this after I opened the file!

I also noticed that you used the brep before I isolated the exterior surfaces. Would it matter which one I use?

Thank you,

Did you change anything?
I dowloaded the script I gave you and everything is fine, maybe try re-running this little guy:

The image you uploaded shows some kind of problem with the flip component, put a panel in the output and show me what it says

As a friend of mine says, if you have to do a mess like this, you are clearly doing something wrong.

I just ignored that block of the script because it seemed useless, nothing is getting done there and you are misusing the component…

The main idea is rebuilding the surfaces to make some untrimmed surfaces. If my script doesn’t work (weird, it works for me) just try to copy this steps

Best regards,
Sir Ernest Shackleton

As @shackleton mentioned, there are so many topics about your problem, whenever you feed a Trimmed Surface into Isotrim component (and lots of other components) it works on underlying Untrimmed Surfaces.

Maybe you can achieve what you’re looking for by using mirrorCutPolysurface from pufferfish plugin:

IsoTim (21.5 KB)


Wow so, fancy! When I grow up, I want to make that kind of videos. Kudos!

Hi Shackleton,

It still isn’t working for me after copying your steps :frowning: Thank you for your help anyways!

Hi Mahdiyar,

This is for a school project and we are not allowed to use plugins but thank you! (22.9 KB)

1 Like

i just love the video
how u made it
and the solution really simple and the best !!