[vtkusers] wedge: different node ordering

[Nico Schlömer]

Hi everyone,

Recently, a meshio user came up with an interesting problem in wedge node
ordering when reading VTK files. The VTK specification [2] lists this [3]
ordering, but a file in the wild had that [4]. They look almost identical
at first sight, and in fact they both list wo triangles, where the `k`th
node of the first is connected to the `k`th node of the second. In the
ordering in the specification, however, the second triangle normal points
towards the first triangle, while in the the other, the first triangle
normal points towards the second triangle.

ParaView will happily display both variants, but I'm wondering if the
second case if formally covered by the specification.

(The issue was discovered when doing FEM computations where the second
variant led to negative Jacobians.)

Cheers,
Nico

[1] https://github.com/nschloe/meshio/issues/185
[2] https://www.vtk.org/wp-content/uploads/2015/04/file-formats.pdf
[3]
https://user-images.githubusercontent.com/9031253/35021239-dbb37d7a-fae4-11e7-8534-167726495bd8.png
[4]
https://user-images.githubusercontent.com/181628/35061681-40a8ee76-fbc2-11e7-9fe3-caeff268738a.png
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://vtk.org/pipermail/vtkusers/attachments/20180119/6fbd048f/attachment.html>