[vtkusers] Re: Mapping/Interpolate scalars in a suitable way on a Finite Element Mesh

[Steve Joyce]

Hi,

The interpolation is by colour rather than by value by default.
However, I've obtained reasonable results using a
vtkBandedPolyDataContourFilter, which uses the value interpolation
defined for the cell type to create sub-cells of a given scalar value,
which are then coloured. The number of sub-cells depends on your node
values and the number of values you have specified for the filter. It
works like a normal contour filter, but fills in the contours with the
appropriate colour (hence the name). Note that point scalars get
converted to cell scalars by this filter. I've only tried this for
linear hexahedrons so far.

Steve

>>> vtkusers-request at vtk.org 14/10/2004 15:26:16 >>>

------------------------------

I have read in a mesh from a Finite Element solver, into VTK and now I
want to map the stresses( point scalars) in a suitable way. The values
are mapped correctly in the points(nodes) but the interior of the cell
looks bad.

I have attached two pictures that shows the mapping. As seen in the
images, the diagonal of the quads has a constant value i.e. the result
is interpreted as two planar triangles. In a case with a quad element
and with a non-planar response surface this is not a good
representation. 


I want the mapping to be like a contour filter that clearly show the
stresses around a certain point(s). Any suggestions? Is it possibly to
somehow use the contourfilter on my scalars?




code extraction...


this->lut=vtkLookupTable::New();
this->lut->SetTableRange(this->filereader->GetOutput()->GetScalarRange());
this->lut->SetHueRange(0.667, 0.0);
this->lut->Build();


this->bar=vtkScalarBarActor::New();
this->bar->SetLookupTable(lut);
this->bar->SetNumberOfLabels(8);



this->pMapper=vtkPolyDataMapper::New();
this->pMapper->SetInput(gFilter->GetOutput());
this->pMapper->SetLookupTable(lut);
this->pMapper->SetScalarRange(this->filereader->GetOutput()->GetScalarRange());


// furhter down the pipeline..


this->actor->SetMapper(dataMapper);
//this->actor->GetProperty()->SetInterpolationToFlat();
this->actor->GetProperty()->SetInterpolationToGouraud();
this->actor->GetProperty()->SetAmbient(0.4);
this->actor->GetProperty()->SetDiffuse(0.2);
this->actor->GetProperty()->SetSpecular(0.2);
.....

Best Regards,

Peter


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