[vtkusers] On volume rendering

[cspl]

Dear  Friends,

I am working on volume rendering.I am using composite technique.It is working fine.But I want make it fast.
It is too slow  when I rendered large volume(around 120 slices).I have written code as follows.Please give me suggestion.

void Composite(LPSTR FileName,HWND m_hWnd)
{


 DICOMReader DCMReader;
 DCMReader.StaticVarInit(); 
 ///Read the Dicom file
 BOOL flag=DCMReader.ReadDicomImage(FileName); 
 //samples per pixel
 const char *samples=DCMReader.GetDicomInfo(cs_samples_pixel);

 float VoxelDepth = 1;
 double VoxelWidth = 1,VoxelHeight = 1;
 //dataspacing in x,y direction 
 char *Spacing = DCMReader.GetDicomInfo(cs_pixel_spacing);
 //dataspacing in z direction
 char *ChrVDepth = DCMReader.GetDicomInfo(cs_slice_thickness);
 
 if(strcmp(ChrVDepth," ") != 0)
  VoxelDepth = atof(ChrVDepth);

 if(strcmp(Spacing," ") != 0)
  GetVoxelSpacing(Spacing,VoxelWidth,VoxelHeight);
 
 ///get image data pointer
 unsigned char* Buffer = (unsigned char *) DCMReader.GetAllImageData();  
 int spp=atoi(samples);
 ///calculating the volume size
 long ImageSz = DCMReader.width  * DCMReader.height *DCMReader.Slices;
 long in_max,in_min;
 
 renderer1 =vtkRenderer::New();
 renWin1=vtkRenderWindow::New();
 
 // Vtk Class to import the Buffer for furthur operations on volume.
 
 vtkImageImport *Importer = vtkImageImport::New();
 
 Importer->SetDataExtent(0, DCMReader.width - 1, 0, DCMReader.height- 1, 0, DCMReader.Slices - 1);
 Importer->SetWholeExtent(0, DCMReader.width - 1, 0, DCMReader.height- 1, 0, DCMReader.Slices - 1);
 Importer->SetDataSpacing((float)VoxelWidth,(float)VoxelHeight,(float)VoxelDepth);
 Importer->SetNumberOfScalarComponents(spp);
 // Set the Appropriate Data Type to the Importer Object
 if(DCMReader.DataType==DCMUShort) 
 {
  
  //Find the max,min values of Input Images
  FindMinMax((unsigned short*)Buffer,ImageSz,&in_max,&in_min);
  Importer->SetDataScalarTypeToUnsignedShort();
  
 }

 if(DCMReader.DataType==DCMShort) 
 {
  
  //Find the max,min values of Input Images
  FindMinMax((short *)Buffer,ImageSz,&in_max,&in_min);
  Importer->SetDataScalarTypeToUnsignedShort();
 }

 if(DCMReader.DataType==DCMUChar) 
 {
  //Find the max,min values of Input Images
  FindMinMax((unsigned char *)Buffer,ImageSz,&in_max,&in_min);
  Importer->SetDataScalarTypeToUnsignedChar();
 }

 if(DCMReader.DataType==DCMChar) 
 {
  //Find the max,min values of Input Images 
  FindMinMax((char *)Buffer,ImageSz,&in_max,&in_min);
  Importer->SetDataScalarTypeToUnsignedChar();
 }


 Importer->SetImportVoidPointer(Buffer);   // Importing the Buffer
 
 //to get first image display once again flip the image
 vtkImageFlip *upsidedownflip=vtkImageFlip::New();
 upsidedownflip->SetInput(Importer->GetOutput());
 upsidedownflip->SetFilteredAxes(2);

 vtkImageFlip *fronttobackflip=vtkImageFlip::New();
 fronttobackflip->SetInput(upsidedownflip->GetOutput());
 fronttobackflip->SetFilteredAxes(1);

 //Create a transfer function mapping scalar value to opacity
    vtkPiecewiseFunction *oTFun = vtkPiecewiseFunction::New();
  oTFun->AddSegment(0, 0.0, in_max, 1.0);
 

   //Create a transfer function mapping scalar value to color (grey)
    vtkPiecewiseFunction *cTFun = vtkPiecewiseFunction::New();
 cTFun->AddSegment(0, 0.5, in_max, 1.0);
 
    
   // Create a property for the volume and set the transfer functions.
   // Turn shading on and use trilinear interpolation
 vtkVolumeProperty *volumeProperty = vtkVolumeProperty::New();
 volumeProperty->SetScalarOpacity(oTFun);
 volumeProperty->SetAmbient(0.10);
 volumeProperty->SetDiffuse(0.40);
 volumeProperty->SetSpecular(0.50);
 volumeProperty->SetSpecularPower(100);
 volumeProperty->SetInterpolationTypeToLinear();
                  volumeProperty->ShadeOn();

 
 vtkVolumeRayCastMapper *volumeMapper=vtkVolumeRayCastMapper::New(); 
 vtkVolumeRayCastCompositeFunction *Composite=vtkVolumeRayCastCompositeFunction::New(); 
 Composite->SetCompositeMethodToClassifyFirst();
 volumeMapper->SetInput(fronttobackflip->GetOutput());
 volumeMapper->SetVolumeRayCastFunction(Composite);///for Composite Technique

 vtkLODProp3D *lod=vtkLODProp3D::New();
 lod->AddLOD(volumeMapper,volumeProperty,0.0);
 lod->SetPosition(0,1,2);
 lod->SetScale(3,3,3);
 renderer1->AddProp(lod);

 renWin1->AddRenderer(renderer1);
 ///Client window handle to vtk Render window
 renWin1->SetParentId(m_hWnd);
 renderer1->GetActiveCamera()->Azimuth(20.0);
 renderer1->GetActiveCamera()->Dolly(1.60);
 renderer1->ResetCameraClippingRange();
 
 renWin1->SetSize(DCMReader.width-10,DCMReader.height-10); 
 float rate=renWin1->GetDesiredUpdateRate();
 renWin1->SetDesiredUpdateRate(2.0);
 renWin1->Render();  
 
 iren1 =vtkRenderWindowInteractor::New();
  // Interact with the data at 2 frames per second
 iren1->SetRenderWindow(renWin1);
 iren1->SetDesiredUpdateRate(2.0);
 iren1->SetStillUpdateRate(0.001);
 iren1->Initialize();
 //clean the vtk objects
 Importer->Delete();
 fronttobackflip->Delete();
 upsidedownflip->Delete();
 Composite->Delete();
 oTFun->Delete();
 cTFun->Delete();
 volumeProperty->Delete();
 volumeMapper->Delete();
 volume1->Delete();
}

thanking you,

Regards,
Ramakrishna
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