Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

"Difference" operation destroys Bezier curvature

Please login with a confirmed email address before reporting spam

Good Evening,
In 2D modeling, I find that when I take the difference between two solids then some lines that were originally drawn as Bezier curves become straight -- they lose their curvature and are rendered as simple straight lines. This isn't just a rendering issue, since all subsequent meshing and solutions obey the new straight boundaries. How can I preserve my curvature?? Note that my resulting solid object does have a wide distribution of feature sizes, with lines varying in length from 200 to 0.02 m. Also note that this problem doesn't happen every time, although I haven't yet been able to figure out exactly what conditions cause it.
Many Thanks,
Rafael

2 Replies Last Post Mar 30, 2011, 7:31 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 30, 2011, 1:43 a.m. EDT
Hi

have you checked the relative tolerance value, sometimes it needs to be adapted (might not be the issue) ?

--
Good luck
Ivar
Hi have you checked the relative tolerance value, sometimes it needs to be adapted (might not be the issue) ? -- Good luck Ivar

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 30, 2011, 7:31 a.m. EDT
Thanks Ivar,

The relative tolerance was not the problem -- adjusting it didn't change the resulting solid. But I found that by restricting the maximum mesh size on the two straightened lines their curvature is "recovered" after meshing. Strange that they would be rendered straight until a fine mesh is created, rather like the model rendering is anticipating the expected mesh size. But problem solved.

Best,
Rafael
Thanks Ivar, The relative tolerance was not the problem -- adjusting it didn't change the resulting solid. But I found that by restricting the maximum mesh size on the two straightened lines their curvature is "recovered" after meshing. Strange that they would be rendered straight until a fine mesh is created, rather like the model rendering is anticipating the expected mesh size. But problem solved. Best, Rafael

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.