[vtkusers] Announcement: New image rendering classes for VTK

[David Gobbi]

Hi Dzenan,

For your code, my guess is that the "translation" part of the 4x4
matrix should be set to something like the origin multiplied by the
rotation matrix, but there might be other little details that you need
to take care of.  My only suggestion is that you don't try to fix it
through trial-end-error.  Use pencil-and-paper to work through the
math.

 - David

2011/6/29 Dženan Zukić <dzenanz at gmail.com>:
> Hi David,
>
> with this I try to do what you suggested, i.e. consider VTK's world
> coordinate system as DICOM patient coordinate system:
> //red is the transformation-related code
> void MainWindow::updateVisualization()
> {
>     typedef itk::ImageToVTKImageFilter<VisualizingImageType>
> itkVtkConverter;
>     itkVtkConverter::Pointer conv=itkVtkConverter::New();
>     conv->SetInput(logic->visualizing);
>     vtkGPUVolumeRayCastMapper *mapper = vtkGPUVolumeRayCastMapper::New();
>     mapper->SetInput(conv->GetOutput());
>     if (volume)
>         volume->Delete();
>     volume=vtkVolume::New();
>     volume->SetProperty( myTransferFunction );
>     volume->SetMapper( mapper );
>     mapper->SetBlendModeToComposite();
>     VisualizingImageType::DirectionType
> d=logic->visualizing->GetDirection();
>     vtkMatrix4x4 *mat=vtkMatrix4x4::New();
>     for (int i=0; i<3; i++)
>         for (int k=0; k<3; k++)
>             mat->SetElement(i,k, d(i,k));
>     mat->SetElement(3,3, 1);
>     VisualizingImageType::SpacingType sp = logic->visualizing->GetSpacing();
>     VisualizingImageType::PointType origin=logic->visualizing->GetOrigin();
>     for (int i=0; i<3; i++)
>         mat->SetElement(i,3, origin[i]/sp[i]);
>     volume->SetUserMatrix(mat); //orientation and size OK, position wrong
>     vtkRenderer *renderer =
> vis->GetRenderWindow()->GetRenderers()->GetFirstRenderer();
>     renderer->RemoveAllViewProps();
>     renderer->AddVolume( volume );
>     defaultCameraPos(); //centers view on the volume, looking at it from
> left
>     vis->GetRenderWindow()->Render();
>
> vis->GetRenderWindow()->GetRenderers()->GetFirstRenderer()->ResetCamera();
> }
> The polygonal data is in DICOM's patient coordinate system (vertex positions
> from itk::Image->TransformIndexToPhysicalPoint() etc). The orientation is
> correct, but I can't get the position correctly. I have tried
> -origin[i]/sp[i], origin[i]*sp[i], origin[i], -origin[i], -2*origin[i] and
> similar combinations but none of them worked. Any suggestion to what am I
> doing wrong?
> Regards,
> Dženan
> 2011/6/29 David Gobbi <david.gobbi at gmail.com>
>>
>> On Tue, Jun 28, 2011 at 9:40 AM, Dženan Zukić <dzenanz at gmail.com> wrote:
>> > Hi David,
>> >
>> > I am interested in this too:
>> > Does the above approach affect the polygonal actors in the scene
>> > (segmented
>> > parts of the image)?
>> > Regards,
>> > Dženan
>>
>> When the DICOM patient coordinate system is used as the VTK world
>> coordinate system, the assumption is that everything (images AND
>> polydata) would have a either already be in the patient coordinate
>> system, or if not, you would to have a 4x4 transform to set as the
>> actor's UserMatrix (or UserTransform).  I.e. a transform to bring the
>> data from its original coordinate system into the patient coordinate
>> system.
>>
>>  - David
>
>