[vtkusers] Setting scalar point attributes in a contour

[Marc Cotran]

Hi Christian,

For 1) - You can use vtkMassProperties to get the number of polygons in 
your isosurface. You may wish to use a vtkTriangleFilter first to ensure 
that only triangle polys are present. You can also look at the 
vtkPolyData instance directly. In your case, 
yourContourFilter->GetOutput() is a vtkPolyData instance, which is 
composed of:

    * Points - a vtkPoints instance defining the geometry of the isosurface
    * Cells - 4 vtkCellArray instances defining how the points are
      connected together to make the isosurface's triangles, vertices,
      lines, and triangle strips

You can either vtkPolyData::GetNumberOfPolys() or 
vtkPolyData::GetPolys()::GetNumberOfCells. Before using any of these 
methods, make sure you Update() the pipeline (eg. 
yourContourFilter->Update) .

For 2) - Take a look at vtkFieldData and vtkDataObject (of which 
vtkPolyData is a subclass). You can create your attribute scalar data 
for the points as a vtkFieldData object, and then 
vtkDataObject::SetFieldData with that object. You may wish to 
vtkMapper::SetScalarVisibility(1) in order to visualize the scalars. If 
you do so, you will need to vtkMapper::SetLookupTable as well.

hth

Marc

Christian Zemlin wrote:
> Dear vtk-experts,
>  
> I would like to assign a scalar attribute to each vertex of an 
> isosurface that I generated using vtkContourFilter.
> 1) How can I determine the number of triangles that a contour consists 
> of ?
> 2) How can I assign scalar properties to a particular vertex of a contour?
>  
> Thank you,
>  
> Christian
>
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