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Re: UFL cell normal implementation

 

Shawn Walker wrote:

On Mon, 14 Sep 2009, Peter Brune wrote:



On Mon, Sep 14, 2009 at 3:47 AM, Anders Logg <logg@xxxxxxxxx> wrote:
On Fri, Sep 11, 2009 at 12:56:26PM -0500, Peter Brune wrote:
> Hey -
>
> Here's my bundle for the cell normals in FFC. There are a couple issues: > When I was calculating the direction of the normal, remove_unused was getting > rid of the unused normal code, but not the unused boolean direction variable. > Other than that, I've tested it on a few things, but not with restriction; > however; it should work just like the facet jacobian code w.r.t. this and I
> wrote it so that it should theoretically work.
>
> - Peter

Nice. I'm just wondering how the facet normal is defined here. Is it
consistent with the UFC numbering?


It behaves like the FacetNormal in SpecialFunctions, so it doesn't orient a particular facet. Is there a
particular reason to have it do that?

- Peter

I think it may be important for H(div) elements, where there is a fixed orientation for each edge segment in the mesh (for 2-D triangulations). But I could be wrong...

The implementation of the H(div) and H(curl) elements is based on having a consistent edge/normal orientation. In particular, that two facets agree on the direction of the normal component.

So yes, it matters.

--
Marie


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