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"Difference" operation destroys Bezier curvature

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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 30 mar 2011, 07:31 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 30 mar 2011, 01:43 GMT-4
Hi

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

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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

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Posted: 1 decade ago 30 mar 2011, 07:31 GMT-4
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

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