Spreadsheet view and mesh data

[ragdollfun]

Hello everyone,

I’m encountering an issue with the way ParaView displays mesh data in the spreadsheet view.

The data I am visualizing is stored in a STL file. From what I know, STL files describe every face of a surface mesh as a separate entry in the following scheme:

facet normal ni nj nk
    outer loop
        vertex v1x v1y v1z
        vertex v2x v2y v2z
        vertex v3x v3y v3z
    endloop
endfacet

i.e. a total of 12 components (or 4 3-components).

Paraview’s spreadsheet view, on the other hand, reduces this to 4 components (not counting the “Point ID”).

Can someone help me understand what is happening here ? Is Paraview’s spreadsheet view simply displaing every individual vertex ? (with duplicates ?)

Or is there something else going on ? Because there is another thing bothering me when using the “Cell Centers” filter: if Paraview’s spreadsheet view is simply displaying the vertices, then why is there more entries after using the “Cell Centers” filter instead of less ? (there should be 3 vertices per face => a 3-fold reduction of the spreadsheet size)

Please, can someone help me understand how Paraview and its spreadsheet view work with mesh data ?

[Kenichiro-Yoshimi (Kyoshimi)]

Hello,

You may want to check the information in the STL data consisting of one triangle (one normal vector and the coordinates of the three vertices) and its correspondence in the Spread Sheet of ParaView.

At first, the coordinates of the three vertices can be seen in the Spread Sheet.

Next, when Attribute is changed to Cell Data, the figure below shows that the information on the normal vector of the triangle is lost. However, this can be restored with the Generate Surface Normals filter.

[ragdollfun]

So ParaView does decouple the vertices that compose a cell, so to speak. I can’t say I’m not a little disappointed, though I can understand that in a mixed mesh (with triangular, quadrangular and other-angular elements) doing otherwise might be difficult.