Make ArbitraryOrderLagrangeElement VTK-compatible

[adtzlr]

• Elements with order > 2

closes #701

import felupe as fem
import pyvista as pv

cube = fem.mesh.CubeArbitraryOrderHexahedron(order=5)
region = fem.RegionLagrange(cube, order=5, dim=3)
field = fem.FieldContainer([fem.Field(region, dim=3)])
cube.plot(opacity=0.9).show()

boundaries, loadcase = fem.dof.uniaxial(field, clamped=True, move=-0.3)

solid = fem.SolidBody(umat=fem.NeoHooke(mu=1, bulk=5), field=field)
step = fem.Step(items=[solid], boundaries=boundaries)
job = fem.Job(steps=[step]).evaluate()

surface = field.plot().mesh.separate_cells().extract_surface(nonlinear_subdivision=4)
edges = surface.extract_feature_edges()

plotter = pv.Plotter()
plotter.add_mesh(surface)
plotter.add_mesh(edges, style="wireframe", color="black", line_width=3)
plotter.show()

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.43%. Comparing base (6e46c49) to head (5335ca3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #702   +/-   ##
=======================================
  Coverage   97.42%   97.43%           
=======================================
  Files          94       94           
  Lines        5014     5033   +19     
=======================================
+ Hits         4885     4904   +19     
  Misses        129      129           

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[adtzlr]

This is from ParaView, order=3

[adtzlr]

The lagrange hexahedron must be modified. According to the screenshot, this is a linear hexahedron and then a grid without the corner vertices.

Warning: It seems that ParaView uses a different sorting than PyVista!?

[adtzlr]

Furthermore, the point ordering is different among VTK versions. https://discourse.julialang.org/t/writevtk-node-numbering-for-27-node-lagrange-hexahedron/93698/9