[vtkusers] Announcement: New image rendering classes for VTK

[Dženan Zukić]

I did the math, and it should be as simple as this:

VisualizingImageType::DirectionType d=logic->visualizing->GetDirection();
vtkMatrix4x4 *mat=vtkMatrix4x4::New(); //identity matrix
for (int i=0; i<3; i++)
    for (int k=0; k<3; k++)
        mat->SetElement(i,k, d(i,k));
VisualizingImageType::PointType origin=logic->visualizing->GetOrigin();
for (int i=0; i<3; i++)
    mat->SetElement(i,3, origin[i]);
//mat->Invert(); //inverse produces even wrong orientation
volume->SetUserMatrix(mat);

However this does not work. This is a simple transformation from scaled
index space (vtkVolume handles spacing) to DICOM physical space. If no one
has any suggestion, I will simply have to create a system of linear
equations from which to construct the VTK's transform matrix. And equations
I will have to obtain by passing a number of points through ITK's
transformation and add some simple objects to the vtk scene at that spot and
on index space spot but with VTK transformation applied.

Regards,
Dženan

2011/6/29 Dženan Zukić <dzenanz at gmail.com>

> I tried trial and error: premultiply translation, postmultiply, divide by
> and multiply by spacing, all that unsuccessfully. Now I need to work out the
> math :D
>
> 2011/6/29 David Gobbi <david.gobbi at gmail.com>
>
>> 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
>> >
>> >
>>
>
>
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