[vtkusers] Assigning colors to scalars

[Lise Angell]

Hi Jens,

Thanks for your reply.
I've tried what you suggested, but I still don't get the wanted result...

My unstructuredGrid is made from a vtkPoints and a vtkDoubleArray
object, and the grid (and the scene) is updated as several scalar
fields are read from file.

With:
	# allocate VTK structures
	vtk_field = vtk.vtkUnstructuredGrid()
	pts = vtk.vtkPoints()					# coordinates
	pts.SetNumberOfPoints(nno)
	data = vtk.vtkDoubleArray()				# data
	data.SetNumberOfValues(nno)
	data.SetName('Values')

       [...]  # read node and coordinate info

	vtk_field.SetPoints(pts)
	vtk_field.GetPointData().SetActiveScalars('Values')

       [...]  # mount graphics stuff

	lut = vtk.vtkLookupTable()
	lut.SetNumberOfColors(10)
	#lut.SetTableRange(scalar_range[0], scalar_range[1])
	lut.SetHueRange(0.0, 0.3)
	#lut.SetSaturationRange(0, 0)
	#lut.SetValueRange(0.2, 1.0)
	lut.Build()
	
	mapper = visualize(renderer, vtk_field, nsd)
	#mapper.SetScalarRange(vtk_field.GetScalarRange())    # gives [0,1], wrong
	mapper.SetScalarRange(scalar_range) # contains min,max of the scalar fields
	mapper.SetLookupTable(lut)

       for each scalar field:
              [read field from file into vtk_field]
              vtk_field.Update()
		mapper.Update()
		renWin.Render()


What is the difference between SetScalars and SetActiveScalars?

Lise


P.S: Concerning your question, I would think it would be enough to
update the pipeline with the grid's Update() function and then
Render(), but if you say it doesn't work I really don't know (it might
turn out I've got the same problem as you)...



On 11/6/05, Jens <jens-devel at gmx.de> wrote:
> Hi Lise
> you need to call
> u_field->GetPointData()->SetActiveScalars("attribute-name");
> mapper->SetScalarRange(u_field->GetScalarRange());
> ,too.
> This works for me as long as I call all functions before Render().
> (and remove SetTableRange(...) )
>
>         Greetings
>                 Jens
> P.S:
> Please read my mail  "How to change the active cell attribute after "Render()"
> I wrote just before your mail and give me an answer for that ...
>
> Am Sonntag, 6. November 2005 21:00 schrieb Lise Angell:
> > Dear vtk-users,
> >
> > I'm working with a 3D dataset containing a heart model. This model is
> > read into vtk as an UnstructuredGrid with a scalar value in each
> > point.
> > I would like to color the model according to these scalars. I've tried
> > vtkLookupTable, setting the table range to the min and max value of
> > the scalar values, but the model still turns out all red...
> >
> > This is (parts of) my code, I would be grateful for any advise:
> >
> >
> > # scalar_range contains min and max value in the unstructured grid u_field
> > lut = vtk.vtkLookupTable()
> > lut.SetNumberOfColors(10)
> > lut.SetTableRange(scalar_range[0], scalar_range[1])
> > lut.SetHueRange(0.0, 0.3)
> > lut.Build()
> >
> > mapper = vtk.vtkDataSetMapper()
> > mapper.SetInput(u_field)
> > mapper.SetLookupTable(lut)
> >
> >
> >
> > Best regards,
> > Lise
> >
> > --
> > "Je forme une entreprise qui n'eut jamais d'exemple,
> > et dont l'exécution n'aura point d'imitateur."  J-J Rousseau
> > _______________________________________________
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--
"Je forme une entreprise qui n'eut jamais d'exemple,
et dont l'exécution n'aura point d'imitateur."  J-J Rousseau