[vtkusers] xml data extraction

[Mathieu Malaterre]

Paul Cochrane wrote:
> Hi all,
> 
> I'm a newbie to vtk, and have a question concerning the process of reading
> data from vtk xml files into vtk so that I can then manipulate and view the
> data.
> 
> The vtk xml file contains an UnstructuredGrid, with Points for the locations
> of the data, PointData containing the scalar values of the data at those
> points, and various CellData elements containing tags, and connectivity etc.  
> The process that I'm using is to read the data in like so:
> 
> reader = vtk.vtkXMLUnstructuredGridReader()
> reader.SetFileName("geom26.xml")
> 
> But then I run into my first wall.  What do I do then? I assume that I
> should use some kind of data mapper, so I'd do something like:
> 
> particleMapper = vtk.vtkDataSetMapper()
> particleMapper.SetInput(reader.GetOutput())
> 
> But what data out of the UnstructuredGrid did I just grab?  I want to
> generate spheres at the locations of the Points, with radii from the
> PointData, and use other attributes defined in the CellData to specify such
> things as colour etc.  How do I do this?  
> 
> I have read the vtk User's Guide, and _many_ of the examples, but it still
> isn't clear to me how vtk thinks.  I.e. where do I pipe what data to what
> object (and importantly why?).

You can always use the Print method to 'show' your vtk object.

ex:

...
reader.Update()
print reader.Print()


Otherwise VTK by default display wireframe or surface, so you'll need to 
glyph your unstructured grid with sphere to see the point.

Maybe a simplier approach would be to use paraview(*). Once you play 
with it it is very easy to generate tcl script that will dump which vtk 
classes where used.

HTH
Mathieu
(*) http://paraview.org