Invalid surface

The attached surface comes from a huge IGES import from NX.
When I run _SelBadObjects more or less 50% appear to be “Invalid surfaces”.
What makes this surface invalid and what problems can I expect?
It is apparently a trimmed surface.

Happy to hear from you!

Invalid surface example.3dm(126.1 KB)

Dunno what makes it bad. But it’s easy to fix.

Shrinktrimmedsurface, detachtrim, explode trim crv, rejoin.

Then retrim with the ‘rebuilt’ curve.

Invalid surface exampleCK.3dm(115.4 KB)

Invalid surface exampleCK.3dm(115.4 KB)

This is a typical bad trim, in the trim curve there are micro segments smaller than the file tolerance. Just untrimming and retrimming usually fixes it…

The attached script should allow you to fix multiple surfaces at once. It is SUPPOSED to temporarily turn off CheckNewObjects and turn it back on again at the end, but I see that is not working. This may be a Rhinoscript bug, so you may need to turn it off manually before starting and turn it back on at the end - until I figure out why it’s doing that.



RetrimSrfs.rvb(2.8 KB)

1 Like

Hi Chris and Mitch,

Thank you for your help and explanation. This is valuable information to fix this large import.
What practical problems can bad trims give when you don’t fix them?