[vtkusers] vtkPolyData to be used with vtkImageStencil.

[Anja Ende]

Another question that I wanted to ask is why do we set the z offset?
Clearly, this is needed as the output is completely different... But what
does it actually do?

Thanks,
Anja

On 25/10/06, Anja Ende <anja.ende at googlemail.com> wrote:
>
> Hi Dean,
>
> Thanks for the reply and code fragmant. This really helps!
>
> Your suggestiosn were completely on the money (as usual!). It was the
> problem with not closing the loop and the extrusion vector just being copied
> and pasted from example code without bothering to understand what it meant!
>
> However, there seems to be a problem with the stencil output:
>
> The points I have chosen are:
>
> float pts[4][3] = {{-55.7812, 9.375, -0.5},
>                 {-18.2812, 49.6875, -0.5},
>                 { 21.0938, 14.0625, -0.5},
>                 {-55.7812, 9.375, -0.5}};
>
> which should form a triangle.
>
> However, the output looks very weird. The triangle is too small and very
> jagged. Also, the dimensions of the triangle seem wrong. There is a
> screenshot attached with this message. Please mail me if you cannot see it
> on the website and I will send you the screenshot immediately.
>
> Also, here is the latest code now:
>
> float pts[4][3] = {{-55.7812, 9.375, -0.5},
>                 {-18.2812, 49.6875, -0.5},
>                 {21.0938, 14.0625, -0.5},
>                 {-55.7812, 9.375, - 0.5}};
>
> vtkFloatArray* pcoords = vtkFloatArray::New();
> pcoords->SetNumberOfComponents(3);
> pcoords->SetNumberOfTuples(4);
> for (int i=0; i<4; i++)
> {
>      pcoords->SetTuple(i, pts[i]);
> }
> // Create vtkPoints and assign pcoords as the internal data array.
> vtkPoints* points = vtkPoints::New();
> points->SetData(pcoords);
> vtkPolyData* polydata = vtkPolyData::New();
> polydata->SetPoints(points);
>
>
>  vtkCellArray* strips = vtkCellArray::New();
>  strips->InsertNextCell(4);
>  strips->InsertCellPoint(0);
>  strips->InsertCellPoint(1);
>  strips->InsertCellPoint(2);
>  strips->InsertCellPoint(3); // same coordinates as the first one..
>
> polydata->SetStrips(strips);
>
> vtkLinearExtrusionFilter* extrude = vtkLinearExtrusionFilter::New();
> extrude->SetInput(polydata);
> extrude->SetScaleFactor(1);
> extrude->SetExtrusionTypeToNormalExtrusion();
> extrude->SetVector(0, 0, 1);
>
> vtkPolyDataToImageStencil* dataToStencil =
> vtkPolyDataToImageStencil::New();
> dataToStencil->SetInput(extrude->GetOutput());
>
> vtkImageStencil* stencil = vtkImageStencil::New();
> stencil->SetInput(m_viewer->GetOutput());
> stencil->SetStencil(dataToStencil->GetOutput());
> stencil->ReverseStencilOn();
> stencil->SetBackgroundValue(0);
>
> stencil->Update();
>
> Also, when I add more points, so instead of a triangle have a
> quadrilateral. I see a triangle shape being stencilled and the outside the
> loop some lines through the image... but they are completely outside the
> loop. However, I can see that the shape is completely closed....
>
> Thanks for all the help!
>
> Anja
>
>


-- 
Cheers,

Anja
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20061025/4c005db9/attachment.htm>