[vtkusers] Re: Re: Creating a Volume from 2D BMP files.

[Sharwari Mavalankar]

hi Yixun,
I implemented the suggestions that you had made.
Now I am getting a 3D volume but it doesnt look anything like the original
2D slices.
It is much darker in appearance and it's got lines all over it ( it looks as
though it's some kind of aliasing).

I have the following questions to ask you
1.While using the function SetDataSpacing(x,y,z) how do I decide the values
of the parameters x,y and z.

2.While using the Addpoint()  function of class vtkPiecewiseFunction what do
the two parameters in the Addpoint function mean?
How do they affect the output?


This is code I have used. Do let me know if you can make any more
sugestions.



//This program reads a single BMP file and plots it as an image.
//The same program will be extended to read multiple images and create a 3D
volume out of 2D slices.


#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkBMPReader.h"
#include "vtkPolyDataMapper.h"
#include "vtkActor.h"
#include "vtkActor2D.h"
#include "vtkImageActor.h"
#include "vtkOutlineFilter.h"
#include "vtkCamera.h"
#include "vtkProperty.h"
#include "vtkPolyDataNormals.h"
#include "vtkContourFilter.h"
#include "vtkDataSetMapper.h"
#include "vtkImageMapper.h"
#include "vtkVolumeMapper.h"
#include "vtkVolumeRayCastMapper.h"
#include "vtkVolumeRayCastCompositeFunction.h"
#include "vtkPiecewiseFunction.h"
#include "vtkVolumeProperty.h"


void main (void)
{

 vtkRenderer *aRenderer = vtkRenderer::New();
    vtkRenderWindow *renWin = vtkRenderWindow::New();

 renWin->AddRenderer(aRenderer);
    vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
    iren->SetRenderWindow(renWin);


 //create an instance of the class vtkBMPReader
 vtkBMPReader *br = vtkBMPReader::New();

 br->SetFilePrefix("C:\\Images\\conductivities\\slice");
 br->SetFilePattern("%s%d.bmp");
 br->SetFileNameSliceOffset(1);
 br->SetFileNameSliceSpacing(1);
 br->SetNumberOfScalarComponents(3);
 br->SetDataSpacing(0.4,0.4,10);
 br->SetDataOrigin(0,0,0);
 br->SetDataExtent(0,255,0,255,0,7);
 br->Update();

    vtkPiecewiseFunction *opacityTransferFunction =
vtkPiecewiseFunction::New();
 opacityTransferFunction->AddPoint(20,0.2);
 opacityTransferFunction->AddPoint(255,1.0);

 vtkVolumeProperty *volumeProperty = vtkVolumeProperty::New();
 volumeProperty->SetScalarOpacity(opacityTransferFunction);




 vtkVolumeRayCastMapper *VolumeMapper = vtkVolumeRayCastMapper::New();
    vtkVolumeRayCastCompositeFunction *RayCastFunction =
vtkVolumeRayCastCompositeFunction::New();
    VolumeMapper->SetVolumeRayCastFunction(RayCastFunction);
    VolumeMapper->SetInput(br->GetOutput());


 vtkVolume *volume = vtkVolume::New();

    VolumeMapper->SetInput(br->GetOutput());
   volume->SetMapper(VolumeMapper);

    vtkCamera *aCamera = vtkCamera::New();
    aCamera->SetViewUp (0, 0,-1);
    aCamera->SetPosition (0, 1, 0);
    aCamera->SetFocalPoint (0, 0, 0);
    aCamera->ComputeViewPlaneNormal();


  aRenderer->AddActor(volume);
 aRenderer->SetActiveCamera(aCamera);
    aRenderer->ResetCamera ();
 aRenderer->SetBackground(1,1,1);
 renWin->Render();

    iren->Initialize();
    iren->Start();

}

Thanks again for all your help.
Sharwari


On 8/31/06, Yixun Liu <yxliu at fudan.edu.cn> wrote:
>
>  Hi,
> Assuming image is 256x256x100. The first file name is image1 and the last
> file name is image100. So, SetDataExtent(0, 255, 0, 255, 1, 100); The access
> violation may be caused by wrong extent setting.
>
> If you use vtkVolume, use vtkVolumeRayCastMapper(vtk4.2.2) or use
> vtkFixedPointVolumeRayCastMapper(vtk5.0). Note that if you use
> vtkFixedPointVolumeRayCastMapper you no need to call
> SetVolumeRayCastFunction();
>
> Hope it help.
>
> Yixun Liu
>
> ----- Original Message -----
> *From:* Sharwari Mavalankar <sharwari at gmail.com>
> *To:* Yixun Liu <yxliu at fudan.edu.cn>
> *Cc:* VTK <vtkusers at vtk.org>
> *Sent:* Thursday, August 31, 2006 6:37 PM
> *Subject:* Re: Creating a Volume from 2D BMP files.
>
>
> hi Yixun,
> Thanks for your email.I had a couple of more questions though.
> 1.I do not want to visualize colour slices.They are grey level images.
>
> 2.Also if I put SetDataExtent() before the Update() then I am getting an
> access violation error.What does the Update function do exactly?
> Also can you tell me what the five parameters in SetDataExtent() mean?
>
> 3.If I use vtkVolume what mapper should I use to visualize the slices?
>
>
> Thanks again for all your help.
> Sharwari
>
>
>
> On 8/23/06, Yixun Liu <yxliu at fudan.edu.cn> wrote:
> >
> >  Hi,
> >
> > If you want to visualize color slices, you need to
> > 1. read these slices. You need to put the SetDataExtent(0, 111, 0, 127,
> > 1, 300);
> > before Update();
> >
> >  vtkTIFFReader *v16 = vtkTIFFReader::New();
> >
> >  v16->SetFilePrefix("D:\\MyVC\\VTKtest\\Raycasting\\Data\\BrainColor\\brain");
> >  v16->SetFilePattern("%s%d.TIF");
> >  v16->SetDataExtent(0, 111, 0, 127, 1, 300);
> >  v16->SetDataSpacing(1.2,1.2,0.5);
> >  v16->SetDataOrigin(0.0, 0.0, 0.0);
> >  v16->SetNumberOfScalarComponents(3);
> >  v16->Update();
> >
> > 2. Add the 4th component. The first three components are color and the
> > 4th is used to map to opacity. I compute the luminancy according to the
> > firft three components and take it as the 4th component.
> >
> > 3. Opacity map using vtkPiecewiseFunction
> >
> > 4. no need color map function
> >
> > 5. you need vtk5.0
> >
> > Regads,
> >
> > Yixun Liu
> >
> >
> >
> >
>
>
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