[Gmsh] $NodeData in msh file ver 4.1

[Christophe Geuzaine]

Dear Cean,

> On 23 Aug 2020, at 03:59, cean wang <ceanwang at gmail.com> wrote:
> 
> Hi,
> 
> Here is a test msh file which has 9 Vector values in $NodeData section.
> 
> When opened with gmsh 4.6.0, it shows 6 vector arrows in element center. I thought it should show 9 arrows at the 9 nodes. What I have done wrong?

By default Gmsh draws vectors at the barycenter of the elements. To draw the arrows at the nodes: Tools->Options->View->Aspect->Glyph location->Node.

> 
> And in Option - View[0] window, Visibility tab, Fields, at the bottom, I could switch to Force Scalar, the result looks weird - not cover the whole domain. What's the number (0-8) on its right used for?

This option allows to draw any component(s) of the field as a scalar, a vector or a tensor.

If you select "Force scalar" and select 0 for the first (and only relevant, for a scalar field) component, you will thus draw the first component (index 0, i.e. the "x" component) of your vector field as a scalar field. The scalar field will be displayed with the same range bounds as the vector field (computed from its norm); hence the "truncation" that you observe. Just set the "min" and "max" values of the range in Tools->View->General->Range mode->Custom. (You can click on the "Min" and "Max" button to automatically recompute the min/max for your particular choice of values to display.)

Christophe

> 
> Regards,
> 
> Cean
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine