# Estimation of triangles above a surface current threshold in .os file

## Recommended Posts

Dear all,

I have Currents.os file. First column contains triangle element number. These are present in increasing order in Currents.os as shown in  an image excerpt below.

Next three columns contain X-, Y- and Z-position of triangles. What location in triangles do these X-, Y- and Z-position refer to?

Also I have attached complete file in the post.

Thanks,

FieldForcer

Currents.tar.xz

##### Share on other sites

Hi @FieldForcer,

The coordinates represent the center points of the mesh triangles.

Best regards,

Torben

##### Share on other sites

Hi Torben,

Area covered by each triangle can be computed from three points that form each triangle. These are not equilateral triangles. Location of three vertices is not mentioned in Currents.os file.  How to obtain location of three vertices/points that form each triangle in POSTFEKO?

Vielen Dank,

FieldForcer

##### Share on other sites

Hi @FieldForcer,

The location of the three vertices is given in the *.os file:

1st column: mesh triangle ID

2nd column: vertice x coordinate

3rd column: vertice y coordinate

4th column: vertice z coordinate

In POSTFEKO you can find a triangle by its ID:

##### Share on other sites

As I understand, each triangle is made by three vertices. For each triangle ID, there should be three X, Y, and Z coordinates. Here there is only one X, Y and Z coordinates for each triangle ID. Earlier you mentioned that these coordinates represent center point of each triangle. Is it possible to directly measure area of triangles in POSTFEKO by sequentially selecting them ?

##### Share on other sites

Hi @FieldForcer,

You're right, sorry. Seems I confused things. In the *.os file the center of the mesh triangles is written. The ID of each triangle can be found in POSTFEKO by using "Find elements". The only way to find out the positions of the vertices of each triangle would be looking up in POSTFEKO. By using "Ctrl+Shift" you can snap the cursor to vertices and read the coordinates in the bottom line.

Could you describe why exactly you want to know the vertices? Maybe there is a different way to achieve your goal.

##### Share on other sites

Hi Torben,

I want to know the vertices because l wish to calculate area of triangles with red color in POSTFEKO. To this end, I can find triangle ID in POSTFEKO. Next I look for their vertices in some FEKO file, and write a subroutine to calculate area occupied by these triangles. How can this be done?

Also faces can be selected in CADFEKO. So I already know face number.

Here I used selection tool to select an arbitrary face, and I can read face number is 30890. Still there is no information about area of selected face.

When I choose multiple faces, I still can't measure combined face area.

Do you understand ?

##### Share on other sites

Hi @FieldForcer,

I don't think there is a direct solution for this in either CADFEKO and POSTFEKO. FEKO does compute the total surface of all mesh elements and reports in the out file. But users can't select certain triangles and calculate that surface only.

One possible (and probably elaborate) workaround could be to create a second model where you exclude all faces where the currents are below a certain threshold. When simulation this reduced model, the total surface will be written to the out file.

##### Share on other sites

Hi Torben,

When I click on mesh, these do not show as triangles, rather as quadrilaterals. How is triangles ID related to quads?

Quote

One possible (and probably elaborate) workaround could be to create a second model where you exclude all faces where the currents are below a certain threshold. When simulation this reduced model, the total surface will be written to the out file.

How can this be done? Please elaborate method.

##### Share on other sites

Hi @FieldForcer,

Mesh IDs are only present in POSTFEKO. They are shown if you press Ctrl+Shift ('snapping keys') and move the mouse over a triangle in a 3D view. The geometry is not present in POSTFEKO. In CADFEKO there is no connection between mesh and mesh IDs (these are created during solving).

Quote

How can this be done? Please elaborate method.

• Solve your Skull model and look at the surface currents in POSTFEKO
• Save the model under different name in CADFEKO
• Delete / Exclude those areas of the geometry where the surface currents are lower than your desired threshold (compare with POSTFEKO).
(you can e.g. add cuboids and then subtract them from the skull, use 'Split', etc.)
• Solve the new model and read the total surface in the out file.

##### Share on other sites

Hi Torben,

I attempted suggested method, and results of surface current density get inconsistent. The method yields inaccurate results. Most importantly, from simulation viewpoint, it requires lot of core hours to re-run entire simulation to estimate surface area. I am wondering if there are any freewares where I can export result file, and pick elements to calculate surface area.

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.