Unmatch between ``mapdl.mesh.grid`` and ``mapdl.mesh``

[germa89]

In the attached model, mapdl.mesh and mapdl.mesh.grid give different results:

In [68]: mapdl.mesh.grid
Out[68]: 
UnstructuredGrid (0x2a900402f40)
  N Cells:      7360
  N Points:     28477
  X Bounds:     -3.175e-02, 3.175e-02
  Y Bounds:     -7.620e-03, 6.858e-02
  Z Bounds:     -3.180e-03, 1.524e-02
  N Arrays:     10

In [69]: mapdl.mesh
Out[69]:
ANSYS Mesh
  Number of Nodes:              7879
  Number of Elements:           7891
  Number of Element Types:      7
  Number of Node Components:    0
  Number of Element Components: 0

This mainly because TARGE170 is missing in _parse_vtk in the pymapdl-reader. See https://github.com/pyansys/pymapdl-reader/pull/129

However, using a pymapdl-reader development branch (feat/adding-target170-elements), I still have different numbers:

In [2]: mapdl.mesh
Out[2]:
ANSYS Mesh
  Number of Nodes:              7879
  Number of Elements:           7891
  Number of Element Types:      7
  Number of Node Components:    0
  Number of Element Components: 0

In [3]: mapdl.mesh.grid
Out[3]:
UnstructuredGrid (0x2390d88be80)
  N Cells:      7891
  N Points:     28479
  X Bounds:     -3.175e-02, 3.175e-02
  Y Bounds:     -7.620e-03, 6.858e-02
  Z Bounds:     -3.180e-03, 1.524e-02
  N Arrays:     10

The issue is mainly with the number of nodes. Without matching numbers, we cannot do:

>>> temp = mapdl.post_processing.nodal_temperatures()
>>> grid = mapdl.mesh.grid
>>> grid.plot(scalars=temp)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Input In [5], in <module>
      1 temp = mapdl.post_processing.nodal_temperature()
      3 grid = mapdl.mesh.grid
----> 4 grid.plot(scalars=temp)

File c:\users\gayuso\other_projects\pyvista\pyvista\plotting\helpers.py:241, in plot(var_item, off_screen, full_screen, screenshot, interactive, cpos, window_size, show_bounds, show_axes, notebook, background, text, return_img, eye_dome_lighting, volume, parallel_projection, use_ipyvtk, jupyter_backend, return_viewer, return_cpos, jupyter_kwargs, theme, hidden_line_removal, anti_aliasing, zoom, **kwargs)
    239         plotter.add_volume(var_item, **kwargs)
    240     else:
--> 241         plotter.add_mesh(var_item, **kwargs)
    243 if text:
    244     plotter.add_text(text)

File c:\users\gayuso\other_projects\pyvista\pyvista\plotting\plotting.py:2228, in BasePlotter.add_mesh(self, mesh, color, style, scalars, clim, show_edges, edge_color, point_size, line_width, opacity, flip_scalars, lighting, n_colors, interpolate_before_map, cmap, label, reset_camera, scalar_bar_args, show_scalar_bar, multi_colors, name, texture, render_points_as_spheres, render_lines_as_tubes, smooth_shading, split_sharp_edges, ambient, diffuse, specular, specular_power, nan_color, nan_opacity, culling, rgb, categories, silhouette, use_transparency, below_color, above_color, annotations, pickable, preference, log_scale, pbr, metallic, roughness, render, component, **kwargs)
   2226 # Scalars formatting ==================================================
   2227 if scalars is not None:
-> 2228     show_scalar_bar, n_colors, clim = self.mapper.set_scalars(
   2229         mesh,
   2230         scalars,
   2231         scalar_bar_args,
   2232         rgb,
   2233         component,
   2234         preference,
   2235         interpolate_before_map,
   2236         custom_opac,
   2237         annotations,
   2238         log_scale,
   2239         nan_color,
   2240         above_color,
   2241         below_color,
   2242         cmap,
   2243         flip_scalars,
   2244         opacity,
   2245         categories,
   2246         n_colors,
   2247         clim,
   2248         self._theme,
   2249         show_scalar_bar,
   2250     )
   2251 elif custom_opac:  # no scalars but custom opacity
   2252     self.mapper.set_custom_opacity(
    144     _custom_opac,
    145 )
    146 table = self.GetLookupTable()
    148 if _using_labels:

File c:\users\gayuso\other_projects\pyvista\pyvista\plotting\mapper.py:263, in make_mapper.<locals>.MapperHelper.configure_scalars_mode(self, scalars, mesh, title, n_colors, preference, interpolate_before_map, rgb, _custom_opac)    261     self.SetScalarModeToUseCellData()    262 else:
--> 263     raise_not_matching(scalars, mesh)
    265 self.GetLookupTable().SetNumberOfTableValues(n_colors)
    266 if interpolate_before_map:

File c:\users\gayuso\other_projects\pyvista\pyvista\utilities\helpers.py:1097, in raise_not_matching(scalars, dataset)        
   1093 if isinstance(dataset, _vtk.vtkTable):
   1094     raise ValueError(
   1095         f'Number of scalars ({scalars.size}) must match number of rows ({dataset.n_rows}).'
   1096     )
-> 1097 raise ValueError(
   1098     f'Number of scalars ({scalars.size}) '
   1099     f'must match either the number of points ({dataset.n_points}) '
   1100     f'or the number of cells ({dataset.n_cells}).'
   1101 )

ValueError: Number of scalars (7879) must match either the number of points (28479) or the number of cells (7891).

Basically it complains of:

ValueError: Number of scalars (7879) must match either the number of points (28479) or the number of cells (7891).

Possible ideas:

• Are we generating middle-side nodes??

[germa89]

It seems related to elements 170 and 174. Probably related to: https://github.com/pyansys/pymapdl-reader/pull/129