[vtkusers] Problems building UnstructuredGrid, desperately needing help!

[Bruno da Silva de Oliveira]

Hi Lise,

 From the code you provided I can't be certain where the problem is. I 
can tell you thought that I have used InsertNextCell(cell_type, id_list) 
and it works fine.

Hmm, looking at the code below, I see that you're inserting the ids of 
the points hard-coded to 1-4... this is mostly certainly wrong. The id 
must be the same id from the vtkPoints that you read the points 
coordinates into... also, don't forget to set them in the 
vtkUnstructuredGrid with SetPoints.

HTH,

Lise Angell wrote:

>Hi everybody!
>
>I'm trying to translate C++ code to Python, but I'm having some
>trouble so I would really appreciate some help (I'm not that
>experienced with VTK).
>
>My program does the following:
>- reads point coordinates and connectivity from file (not a vtk formatted file)
>- builds a vtkUnstructuredGrid and visualizes it.
>
>The problem arises in the building of the unstructuredGrid...
>
>The method
>vtkUnstructuredGrid::InsertNextCell(int type, vtkIdType npts, vtkIdType *pts)
>seems to be unreachable from Python (although it works fine in C++,
>for code sample, see below)...
>When I try to run it I get
>
>Traceback (most recent call last):
>  File "readBinarySimres.py", line 1092, in ?
>    u_field = mount_vtk_structures(fields)
>  File "readBinarySimres.py", line 828, in mount_vtk_structures
>    vtk_field.InsertNextCell(cell_type, npts, pt_list)
>TypeError: function takes exactly 2 arguments (3 given)
>
>
>
>So I tried to use the other method instead,
>InsertNextCell (int type, vtkIdList *ptIds)
>
>for el in range (0,nel):
>  id_list = vtk.vtkIdList()
>  (cell_type, npts, id_list) = convertElm(grid, el, id_list)  #define
>the connectivity in the cell
>  vtk_field.InsertNextCell(cell_type, id_list)
>
>
>def convertElm(grid, e, ids):
>  vtk_cell_type=0; npt=0
>  nsd = grid.nsd; nne = grid.nne
>
>  # check element type
>  elm_type = grid.elm_type
>
>  if elm_type == 'ElmB4n2D':
>    vtk_cell_type = VTK_QUAD
>    #print 'element type ', vtk_cell_type
>    npt = 4
>    ids.InsertNextId(1)
>    ids.InsertNextId(2)
>    ids.InsertNextId(4)
>    ids.InsertNextId(3)
>  [...]
>  return (vtk_cell_type, npt, ids)
>
>
>
>Now I get a Bus error while visualizing (with GeometryFilter,
>WarpScalar, PolyDataNormals and PolyDataMapper)
>
>Any ideas what is wrong or how I can work around this?
>
>Best regards,
>Lise
>
>(Running Mac OSX Tiger, python2.3 and VTK from cvs 11.oct 2005)
>
>###--------------------------------------------------------------------------
>###--------------------------------------------------------------------------
>
>C++ code that works:
>
>   // Grab the grid and related parameters
>  const GridFE& grid = scalar_field.grid();
>  const int      nsd = grid.getNoSpaceDim();
>  const int      nno = grid.getNoNodes();
>  const int      nel = grid.getNoElms();
>
>  // Allocate Vtk data structures for the coordinates and data fields.
>  vtkPoints* pts = vtkPoints::New();
>  pts->SetNumberOfPoints (nno);
>
>  vtkDoubleArray* data = vtkDoubleArray::New();
>  data->SetNumberOfValues (nno);
>  //------------------------------------------------------------------------
>  // First, tell vtk structures about the "geometry" (nodal coords & values)
>  //------------------------------------------------------------------------
>  for (int i = 0; i < nno; i++) {                // run through all nodes
>    s = scalar_field.valueNode(i+1);
>
>    x[0]=grid.getCoor (i+1,1);  // x coordinate of node i+1
>    x[1] = x[2] = scale*s;      // Assumes 1D,  scaled field values as 2nd/3rd
>    if (nsd > 1)
>      x[1]=grid.getCoor (i+1,2);  // y coordinate of node i+1
>    if (nsd  > 2)
>      x[2]=grid.getCoor (i+1,3);  // z coordinate of node i+1
>
>
>    data->SetValue(i,s);      // put field value in vtk object
>    pts->SetPoint(i,x);               // put points in vtk object
>  }
>  vtk_u_grid = vtkUnstructuredGrid::New();
>
>  vtk_u_grid->Allocate (nel,0);                   // set no of elements
>  vtk_u_grid->SetPoints (pts);                    // put points in grid
>  vtk_u_grid->GetPointData()->SetScalars(data);  // put field values in grid
>
>  //---------------------------------------------------------
>  // Next, tell vtk grid structure about the element topology
>  //---------------------------------------------------------
>
>  // Maximum 8 nodes in the allowable Vtk cell types.
>  int vtk_cell_type = 0;
>  int npt = 0, pt_list[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
>
>  for (int e = 1; e <= nel; ++e) {
>    convertElm(grid, e, vtk_cell_type, npt, pt_list);
>    vtk_u_grid->InsertNextCell (vtk_cell_type, npt, pt_list);
>  }
>
>
>
>###--------------------------------------------------------------------------
>###--------------------------------------------------------------------------
>
>
>
>--
>"Je forme une entreprise qui n'eut jamais d'exemple,
>et dont l'exécution n'aura point d'imitateur."  J-J Rousseau
>_______________________________________________
>This is the private VTK discussion list. 
>Please keep messages on-topic. Check the FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
>Follow this link to subscribe/unsubscribe:
>http://www.vtk.org/mailman/listinfo/vtkusers
>
>  
>

-- 
Bruno da Silva de Oliveira
bruno at esss.com.br
ESSS - Engineering Simulation and Scientific Software
http://www.esss.com.br