[vtkusers] MIP VolumeRendering very slow

[Stéphane CALANDE]

Hi,


I've done a very simple MIP-visualizer with VTK 5.2 (Thanks to Aurélie for
the help).

But I'm a little disappointed because it's very slow. The refresh time of
the window is very long.

I make tests with a DICOM Series (36 CT-slices).

Here's the program very simplified :

#include "vtkDICOMImageReader.h"
#include "vtkImageData.h"
#include "vtkImageShiftScale.h"
#include "vtkPiecewiseFunction.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkVolume.h"
#include "vtkVolumeProperty.h"
#include "vtkVolumeRayCastMapper.h"
#include "vtkVolumeRayCastMIPFunction.h"
#include <sstream>

using namespace std;

int main (int argc, char **argv)
{
if( argc < 2 )
{
std::cerr << argv[0] << " rep";
return 1;
}
else
{
string rep;
rep = argv[1];
vtkDICOMImageReader * reader;

reader = vtkDICOMImageReader::New();
string dir("");
ostringstream oss(dir.c_str());
oss << rep ;
dir = oss.str();
const char* adresse = dir.c_str();
reader->SetDirectoryName(adresse);
cout << adresse << endl;
reader->Update();
reader->SetDataScalarTypeToShort();
reader->UpdateWholeExtent();
reader->GetOutput()->UpdateInformation();

vtkRenderer* renderer = vtkRenderer::New();

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

double range[2];
reader->GetOutput()->GetScalarRange(range);
double min = range[0];
double max = range[1];
double diff = max-min;
double slope = 255.0/diff;
double inter = -slope*min;
double shift = inter/slope;
vtkImageShiftScale *vtkImageCast = vtkImageShiftScale::New();
vtkImageCast->SetInput(reader->GetOutput());
vtkImageCast->SetShift(shift);
vtkImageCast->SetScale(slope);
vtkImageCast->SetOutputScalarTypeToUnsignedShort();
vtkImageCast->Update();
vtkImageCast->GetOutput()->GetScalarRange(range);
double level = 0.5 * (range[1] + range[0]);
double window = range[1] - range[0];

vtkPiecewiseFunction *opacityTransferFunction = vtkPiecewiseFunction::New();
opacityTransferFunction->AddPoint( level - window/2  , 0.0 );
opacityTransferFunction->AddPoint( level + window/2 , 1.0 );

vtkPiecewiseFunction *grayTransferFunction = vtkPiecewiseFunction::New();
grayTransferFunction->AddSegment( level - window/2, 0.0 , level + window/2,
1.0 );

vtkVolumeProperty *mipProperty;

mipProperty = vtkVolumeProperty::New();
mipProperty->SetScalarOpacity( opacityTransferFunction );
mipProperty->SetColor( grayTransferFunction );
mipProperty->SetInterpolationTypeToLinear();

vtkVolumeRayCastMIPFunction* mipFunction =
vtkVolumeRayCastMIPFunction::New();
mipFunction->SetMaximizeMethodToOpacity();

vtkVolumeRayCastMapper* volumeMapper = vtkVolumeRayCastMapper::New();

volumeMapper->SetVolumeRayCastFunction( mipFunction );

volumeMapper->SetInput( vtkImageCast->GetOutput() );

vtkVolume* volume = vtkVolume::New();
volume->SetMapper( volumeMapper );
volume->SetProperty( mipProperty );

renderer->AddViewProp( volume );
renderer->Render();

renWin->SetSize( 1000 , 700 );

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

iren->Delete();
renWin->Delete();
renderer->Delete();
return 0;
}
}


and here's the CMakeLists.txt :


PROJECT (Project)
FIND_PACKAGE(VTK REQUIRED)
IF(NOT VTK_USE_RENDERING)
  MESSAGE(FATAL_ERROR "Example ${PROJECT_NAME} requires VTK_USE_RENDERING.")
ENDIF(NOT VTK_USE_RENDERING)
INCLUDE(${VTK_USE_FILE})

ADD_EXECUTABLE(MIP_TEST MIP_TEST.cxx)
TARGET_LINK_LIBRARIES(MIP_TEST vtkVolumeRendering)


To test you just have to give as input a repertory of a DICOM Serie.



My porpose is obviously to create a program more "complicated" than this
one, but it will be impossible if it's so slow.

Do you have any advice, remarks,...? to make it quicker ?


Thank you very much,

Regards,



Stéphane
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