How to convert a mesh to VTK format?

Question

I have a mesh in my own format and I want export it to a .vtk file. How do I do this?

The original mesh is in the following format: (Pseudocode)

class Mesh {

   List<Float[3]> _coordinates

   List<int[4]> _tetra //(elements, Faces, etc.)

}

I hope this clarify my problem. I just want load it with Paraview so I don't care if it is structured, poly, etc.

Answer 1

You may create a vtkUnstructuredGrid:

//vtkPolyData *data = vtkPolyData::New();
vtkUnstructuredGrid *mesh = vtkUnstructuredGrid::New();
vtkPoints *points = vtkPoints::New();
vtkCellArray *cells = vtkCellArray::New();

//vtkIdType pointIDs[4];

std::vector<point>::const_iterator iterator1 = fpoints.begin();

point aux;

if ( event_report != NULL ) { event_report->SetMaxTicks(fpoints.size() + fnodes.size()); }
points->SetNumberOfPoints(fpoints.size());
int pointId = 0;
for (;iterator1 != fpoints.end();iterator1++)
{
    aux = *iterator1;
    points->SetPoint(pointId, aux.coord);
    pointId++;
}

std::vector<node>::const_iterator iterator2 = fnodes.begin();

node aux1;

vtkSmartPointer<vtkIdTypeArray> idCells = 
  vtkSmartPointer<vtkIdTypeArray>::New();
idCells->SetNumberOfComponents(5);
idCells->SetNumberOfTuples(fnodes.size());

int cellIndex = 0;
for (;iterator2 != fnodes.end(); iterator2++)
{
    aux1 = *iterator2;
    vtkIdType * tuple = new vtkIdType[4];
    tuple[0] = 4;
    tuple[1] = aux1.indexs[0] - 1;
    tuple[2] = aux1.indexs[1] - 1;
    tuple[3] = aux1.indexs[2] - 1;
    tuple[4] = aux1.indexs[3] - 1;
    idCells->SetTupleValue(cellIndex, tuple);
    cellIndex++;
}
cells->SetCells(fnodes.size(), idCells);

mesh->SetPoints(points);
mesh->SetCells(VTK_TETRA, cells);

//vtkPolyDataWriter *writer = vtkPolyDataWriter::New();
vtkUnstructuredGridWriter *tetra_writer = vtkUnstructuredGridWriter::New();
tetra_writer->SetFileName( filename );

#if VTK_MAJOR_VERSION <= 5
    tetra_writer->SetInput(mesh);
#else
    tetra_writer->SetInputData(mesh);
#endif

tetra_writer->Write();
tetra_writer->Delete( );

Answer 2

Check out meshio (a project of mine), it'll help you convert meshes from many formats to many others (including VTK). The VTK interface code may give you a clue as to how to customize it.