[vtkusers] vtkBlend Output

[David Gobbi]

Hi Alexis,

The PolyDataToImageStencil filter requires a closed 3D polydata
surface, like a box or a sphere.  It does not work with 2D contours.

I have a "lassoo" class based on some of my old python code for doing
ROI stencils, but it is incomplete.  It would work like
ImplicitSelectionLoop for vtkImageStencilData, but a few hundred times
faster.  I'll take a look at it today to see how much work it would be
to finish it and contribute it to VTK.

  David

On Tue, Nov 2, 2010 at 6:07 PM, Alexis Cheng <acheng_1221 at hotmail.com> wrote:
> Hi David,
>
> It certainly seems to be the Stencil filter that is slowing the system down.
> I am trying to use vtkPolyDataToImageStencil to see if that would be any
> faster, but I'm having some difficulties.
>
> I replaced this ImplicitFunction code:
>
>         vtkSmartPointer<vtkImplicitSelectionLoop> ImplicitLoop =
> vtkSmartPointer<vtkImplicitSelectionLoop>::New();
>         ImplicitLoop->SetLoop(points);
>
>         vtkSmartPointer<vtkImplicitFunctionToImageStencil> dataToStencil =
> vtkSmartPointer<vtkImplicitFunctionToImageStencil>::New();
>         dataToStencil->SetInput(ImplicitLoop);
>
> with this PolyData code:
>
>         vtkSmartPointer<vtkCellArray> polygons =
> vtkSmartPointer<vtkCellArray>::New();
>         vtkSmartPointer<vtkPolygon> polygon =
> vtkSmartPointer<vtkPolygon>::New();
>         polygon->GetPointIds()->SetNumberOfIds(4); //make a quad
>         polygon->GetPointIds()->SetId(0, 0);
>         polygon->GetPointIds()->SetId(1, 1);
>         polygon->GetPointIds()->SetId(2, 2);
>         polygon->GetPointIds()->SetId(3, 3);
>
>         polygons->InsertNextCell(polygon);
>
>         vtkSmartPointer<vtkPolyData> quad =
> vtkSmartPointer<vtkPolyData>::New();
>         quad->SetPoints(points);
>         quad->SetPolys(polygons);
>
>         vtkSmartPointer<vtkPolyDataToImageStencil> dataToStencil =
> vtkSmartPointer<vtkPolyDataToImageStencil>::New();
>         dataToStencil->SetInput(quad);
>
> The final image does not show the stencil with the PolyData code. Is there a
> difference in the implementation of the 2 filters where I would have a
> different output or need a different input? Also, should I expect to see any
> increase in performance by using PolyData instead of ImplicitFunction?
> Thanks for all your answers!
>
> Cheers,
> Alexis Cheng
> Electrical Engineering
> University of British Columbia
>
>
>
>> From: david.gobbi at gmail.com
>> Date: Mon, 1 Nov 2010 19:27:40 -0600
>> Subject: Re: [vtkusers] vtkBlend Output
>> To: acheng_1221 at hotmail.com
>> CC: vtkusers at vtk.org
>>
>> Hi Alexis,
>>
>> Have you tried it without the stencil, for comparison? The
>> vtkImplicitFunctionToImageStencil filter is very slow.
>>
>> David
>>
>>
>> On Mon, Nov 1, 2010 at 5:57 PM, Alexis Cheng <acheng_1221 at hotmail.com>
>> wrote:
>> > Hi all,
>> >
>> > Is vtkBlend extremely resource intensive? I have a following piece of
>> > code
>> > running: FinalImage is a vtkImageData object, MTImage is a vtkImageData
>> > object, and blend1 is a vtkImageBlend object.
>> >
>> >         blend1->SetStencil(dataToStencil->GetOutput());
>> >         blend1->AddInput(MTImage);
>> >         blend1->AddInput(BlackImage);
>> >         blend1->SetOpacity(0,0.5);
>> >         blend1->SetOpacity(1,0.5);
>> >
>> >         if(OutOfView)
>> >         {
>> >             FinalImage = MTImage;
>> >         }
>> >         else
>> >         {
>> >             FinalImage = blend1->GetOutput();
>> >         }
>> >         FinalImage->Update();
>> >
>> > The fps of my display decreases dramatically whenever the output from
>> > blend
>> > is requested. Is this behaviour expected? Thanks in advance.
>> >
>> > Cheers,
>> > Alexis Cheng
>> > Electrical Engineering
>> > University of British Columbia
>> >
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