[vtkusers] Assigning cell values on structured grid

[David Doria]

On Fri, Feb 19, 2010 at 6:30 AM, Sebastian Gatzka <
sebastian.gatzka at stud.tu-darmstadt.de> wrote:

>  Hello.
>
> This time I'm trying to set cell (centroid) values (scalar and vector) to a
> structured grid.
> All the examples I have found set values to the grid points - not the
> cell-centroids.
>
> This should lead to a classical CFD / finite-volume representation of field
> data like temperature, density or velocities.
> So beside the actual assignment to the field I need to know how to display
> the field data, and maybe how to switch between them.
>
> Have a nice day.
> Sebastian
>
>
Sebastian,

You can access cells via their (i,j,k) coordinates using this function:

vtkCell* GetCell(vtkStructuredGrid* grid, int i, int j, int k)
{
  int dims[3];
  grid->GetDimensions(dims);

  if(i < 0 || i > dims[0] - 1 ||
     j < 0 || j > dims[1] - 1 ||
     k < 0 || k > dims[2] - 1 )
    {
    return NULL; // out of bounds!
    }

  int pos[3];
  pos[0] = i;
  pos[1] = j;
  pos[2] = k;

  vtkIdType id;
  id = vtkStructuredData::ComputeCellId(dims, pos);

  return grid->GetCell(id);
}

I'm working on adding it to vtk so you can directly call

grid->GetCell(i,j,k)

Hope this helps,

David
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