# Dividing a Complex Mesh into Different Regions/Subdomains

Asked by Pietro Maximoff on 2010-06-22

Hi

I've got a mesh of a ventricle in the shape of a hollow, irregular prolate spheroid. So, there's an inner and outer radius. I'd like to divide the wall (outer radius to inner radius) into three different layers. Given that the shape is not a perfect sphere or even a perfect ellipsoid, is there a way to do this with DOLFIN or Meshbuilder?

Thanks

Pietro

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2010-06-28
2010-06-28
 Pietro Maximoff (segment-x) said on 2010-06-22: #1

I've just come across the Heart_in_torso mesh in the Meshbuilder samples. What I'm describing is almost the same but mine's only half of that -- just the left ventricle.

So, is it possible to divide my mesh into three layers as I described before?

Pietro

 Johan Hake (johan-hake) said on 2010-06-22: #2

Pietro!

I know that you can apply "inner" surfaces to Tetgen. The generated mesh will
then have vertices laying on this inner surface.

TriTetMesh

branch lp:tritetmesh

is a wrapper for tetgen (and triangle) and generates DOLFIN meshes. If your
outer and inner surfaces are devided into simplices or even rectangles, you
should be able to generate these inner surfaces as parameterized versions of
the outer surface. Did that make sense?

It might be a steep learning cruve getting into TriTetMesh and tetgen, but I

Johan

On Tuesday June 22 2010 01:49:05 Pietro Maximoff wrote:
> Question #115411 on DOLFIN changed:
>
> Description changed to:
> Hi
>
> I've got a mesh of a ventricle in the shape of a hollow, irregular
> prolate spheroid. So, there's an inner and outer radius. I'd like to
> divide the wall (outer radius to inner radius) into three different
> layers. Given that the shape is not a perfect sphere or even a perfect
> ellipsoid, is there a way to do this with DOLFIN or Meshbuilder?
>
> Thanks
>
> Pietro

 Pietro Maximoff (segment-x) said on 2010-06-22: #3

Excellent Johan. This makes sense. I'll download the latest revision of Tritetmesh and have a bit of a play. If I run into any problems, I'll let you know.

Incidentally, is the the HeartinTorso mesh from the Meshbuilder samples that of a human heart ?

Pietro

 Anders Logg (logg) said on 2010-06-22: #4

On Tue, Jun 22, 2010 at 07:11:32PM -0000, Pietro Maximoff wrote:
> Question #115411 on DOLFIN changed:
>
> Pietro Maximoff posted a new comment:
> Excellent Johan. This makes sense. I'll download the latest revision of
> Tritetmesh and have a bit of a play. If I run into any problems, I'll
> let you know.
>
> Incidentally, is the the HeartinTorso mesh from the Meshbuilder samples
> that of a human heart ?

I think so but don't know for sure. I've Cc:ed Ola Skavhaug on this
email. He may know.

--
Anders

 Pietro Maximoff (segment-x) said on 2010-06-28: #5

Hi

I've just loaded my left ventricle mesh into Meshbuilder with the intention of marking the inner (endocardial) surface and the outer (epicardial) surface.

I selected 'Meshfunctions' and then 'face' so I can select faces. When I click on the inner surface though, it selects just a triangle and not the whole face.

Is there a way to select the an entire face in one go without having to select the triangles individually?

Pietro

N.B: I've posted this question on the Meshbuilder page but there doesn't seem to be an answer contact.

 Anders Logg (logg) said on 2010-06-28: #6

On Mon, Jun 28, 2010 at 09:24:12AM -0000, Pietro Maximoff wrote:
> Question #115411 on DOLFIN changed:
>
>
> Pietro Maximoff is still having a problem:
> Hi
>
> I've just loaded my left ventricle mesh into Meshbuilder with the
> intention of marking the inner (endocardial) surface and the outer
> (epicardial) surface.
>
> I selected 'Meshfunctions' and then 'face' so I can select faces. When I
> click on the inner surface though, it selects just a triangle and not
> the whole face.
>
> Is there a way to select the an entire face in one go without having to
> select the triangles individually?
>
> Pietro
>
> N.B: I've posted this question on the Meshbuilder page but there doesn't
> seem to be an answer contact.

Try marking a closed path of triangles and then click on "fill" to
fill the area in between.

Improved functionality for simple selection of entire surfaces (based
on the (dis)continuity of facet normals) might be added in future
versions.

--
Anders