[vtkusers] vtkContourFilter on 2D Cells (vtkPolygon)

[Randall Hand]

Do you want edges of all the polys?  Or just an outer outline of the entire
construct?

If the outer outline is what you want, have you tried the vtkFeatureEdges
filter?

I tried this just now in Paraview (it's great for experimenting with this
kind of stuff, as it's based on VTK).  I loaded an Unstructured Grid with
all 2D cells.  I had to use an "Extract Surface" (vtkDataSetSurfaceFilter)
to get it into a vtkPolyData format, but then I could use the "Feature
Edges" (vtkFeatureEdges) filter.  Turn off all options except "Boundary
Edges", and voila.

On 2/1/06, Frederic DANESI <fred.danesi at netcourrier.com> wrote:
>
>  Dear,
>
> Thanks for this helpful remark… it works now but finally that's not at all
> what I am looking for …
>
> In fact, I would like to find the contour of several polygons … just like
> a boolean operation of  "union", so all points of all polygons have the same
> scalar value. I was hoping that vtkContour would assume something like this
> ….
>
> Have you any idea to do this ? …
>
> Thanks,
>
> Fred.
>
>
>
> You're setting the value of all 4 points to "1", and then taking a contour
> of 1.  It doesn't intersect anywhere, so I think it's working just right.
>
> Change the scalars to:
>   for (int i =0; i <4; i++) scalars->InsertNextValue(i);
>
> And then you'll have 4 different values.
>
> On 2/1/06, *Frederic DANESI* <fred.danesi at netcourrier.com > wrote:
>
> Dear vtkusers,
>
> I am trying something that I believe quite simple, but without any
> success.
>
> I would like to build some vtkPolygons (2D) and then to use
> vtkContourFilter
> to obtain an isoline (which I assume to match with the boundary of all
> polygons together) ...
>
> Even with only one polygon, vtkContourFilter does not do anything
> (vtkContourFilter (09981DD8): Created: 0 points, 0 verts, 0 lines, 0
> triangles) ...
>
> I enclosed my code hereafter.
>
> I will really appreciate any idea, tips on what I missed or what I'm doing
> wrong, or any code example...
>
> Thanks,
> Fred.
>
> ----
>
> vtkPolygon *polygon = vtkPolygon::New();
>
>   polygon->GetPointIds()->SetNumberOfIds(4);
>   polygon->GetPointIds()->SetId(0,0);
>   polygon->GetPointIds()->SetId(1,1);
>   polygon->GetPointIds()->SetId(2,2);
>   polygon->GetPointIds()->SetId(3,3);
>
>   polygon->GetPoints()->SetNumberOfPoints(4);
>   polygon->GetPoints()->SetPoint(0, 0.0, 0.0, 0.0);
>   polygon->GetPoints()->SetPoint(1, 10.0, 0.0, 0.0);
>   polygon->GetPoints()->SetPoint(2, 10.0, 10.0, 0.0);
>   polygon->GetPoints()->SetPoint(3, 0.0, 10.0, 0.0);
>
>   vtkIntArray * scalars = vtkIntArray::New();
>   scalars->Allocate(5000,10000);
>   for (int i =0; i <4; i++) scalars->InsertNextValue(1);
>
>   vtkPolyData * polygonPolyData = vtkPolyData::New();
>   polygonPolyData->Allocate(1,1);
>   polygonPolyData->InsertNextCell(polygon->GetCellType(),
> polygon->GetPointIds());
>   polygonPolyData->SetPoints(polygon->GetPoints());
>   polygonPolyData->GetPointData()->SetScalars(scalars);
>
>   // mapping and rendering "polygonPolyData" ==> OK ...
>
>   vtkContourFilter * flt = vtkContourFilter ::New();
>   flt->SetInput((vtkDataSet *)output);
>   flt->DebugOn();
>   flt->SetValue(0,1);
>
>   //+ mapping and rendering  ==> vtkContourFilter (09981DD8): Created: 0
> points, 0 verts, 0 lines, 0 triangles ... empty ...
>
> --
> Responsable Département DINCCS
> (Département Ingénierie Numérique Conception Collaborative et Simulation)
> Pole de Haute Technologie
> 08000 Charleville-Mézières
> Tél. 03.24.37.89.89
>
>
>
>
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>
> --
> Randall Hand
> Visualization Scientist,
> ERDC-MSRC Vicksburg, MS
> Homepage: http://www.yeraze.com
>



--
Randall Hand
Visualization Scientist,
ERDC-MSRC Vicksburg, MS
Homepage: http://www.yeraze.com
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