Result surface plot issue

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aortizb
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Result surface plot issue

Postby aortizb » Wed Apr 07, 2021 6:16 pm

Hi, when I plot a field that has positive and negative values using "Result surface" option, the 3D plot puts negative values in the +Z direction and positive values in the -Z direction (see the attached figure). Is there any way to switch the axis so that positive values are plotted along +Z direction and negative values along -Z direction?

Thank you.
Alejandro.

gid_plot.png
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escolano
Posts: 1691
Joined: Thu Sep 18, 2014 3:31 pm

Re: Result surface plot issue

Postby escolano » Fri Apr 09, 2021 11:09 am

The surface mesh could be in any 3D location, not compulsory in the XY plane (Z=0) like your example.

The "Result surface" plot is not drawing possitive values along +Z (Z global axis), but along +surface_normal_direction (+z local axis)

It seems that in your example the normal of your triangle/quadrilateral elements is pointing to -Z (its normal is defined by the order of its nodes: "right-hand rule")

And generating the mesh (surface elements) , its normal is the same as the normal of the geometrical surface (its normal depends on its parametrization, the vectorial product of its derivatives: Xu X Xv)

In preprocess you can swap the normal of the surface with the menu:
Utilites->Swap normals->Surfaces

Swap the normals of your surfaces to set them pointing to +Z, just as you want the plot, then re-mesh and re-calculate.


You can also swap normals of mesh elements, in mesh view, but this is discouraged, because if do your re-mesh you will lost your manual changes.

The orientation of the elements is crutial for some kind of simulations, maybe not in your case.
you can also check the normals with the menu:
View->Normals

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