possible bug with 1D high-order Lagrange element

ParaView Support
1

Dear Paraview developers,

I have a mistake with the high-order Lagrange 1D element :
VTK_LAGRANGE_CURVE = 68 in vtkCellType.h
I use the 5.7.0 version of paraview ?

I combine this high-order 1D element with the Tessellate filter
in order to represent a piecewise polynomial 1D curve
in a 2D space or 3D space.

Please find in attachment some snapshots .jpg together
with the .vtk file of what I obtained: results are unexpected.
In comparison, results are right with both
VTK_QUADRATIC_EDGE = 21
VTK_CUBIC_LINE = 35

Please could you explain me if there is a mistake with this example ?
Otherwise, if there is a bug with 1D high-order Lagrange element,
could you please suggest me a way to circumvent it
with my 5.7.0 version of paraview ?

I use paraview as post-processor of the Rheolef FEM C++ library :
https://www-ljk.imag.fr/membres/Pierre.Saramito/rheolef
This library supports intensively high-order elements.

Many thanks for your very nice code and your help,

Pierre

2

Sorry, but the attached files was missing in my previous message:
here is a link to download them:
https://www-ljk.imag.fr/membres/Pierre.Saramito/tmp/lagrange-curve-bug.zip

There are .jpg snapshots and .vtk files for:

  • Lagrange 4th order element
  • Cubic element
  • Quadratic element

Only the Lagrange high-order behaves badly, others are ok;
Thanks by advance for your response,

Pierre