Question

我想在nifti标签集上运行vtkMarchingCubes。我想要生成表面的体素区域都具有相同的值。我有两个问题。首先，我似乎错误地设置了算法，因为生成的vtkPolyData显然没有顶点。其次，我从vtkOBJExporter文档中不清楚如何将vtkPolyData导出为wavefront .OBJ文件。如果有人看到下面的代码有任何问题，或者可以告诉我如何将vtkPolyData导出为OBJ，我将不胜感激。

//Read The Nifti Label File
string input_path = "/MyPath/labels.nii";
nifti_image *im = nifti_image_read(input_path.c_str(),true);
cout<<im->nx<<","<<im->ny<<","<<im->nz<<endl; //Confirms Read Works

// Set up vtk image data
vtkImageImport* importer = vtkImageImport::New();
importer->SetImportVoidPointer((void*)im->data);
importer->SetDataScalarTypeToFloat();
importer->SetDataExtent(0, im->nx-1, 0, im->ny-1, 0, im->nz-1);
importer->SetWholeExtent(0, im->nx-1, 0, im->ny-1, 0, im->nz-1);
vtkImageData* point_cloud = importer->GetOutput();
point_cloud->SetScalarTypeToFloat();
point_cloud->SetExtent(0, im->nx-1, 0, im->ny-1, 0, im->nz-1);
point_cloud->SetSpacing(im->dx, im->dy, im->dz);

//Apply Threshold To Cut Out Other Data 
//Is this needed or will Marching Cubes properly identify the region
vtkImageThreshold* threshold = vtkImageThreshold::New();
threshold->ThresholdBetween(label_number,label_number);
threshold->SetInValue(255);
threshold->SetOutValue(0);
threshold->SetInput(point_cloud);

//Apply the Marching Cubes algorithm
vtkMarchingCubes* marching_cubes = vtkMarchingCubes::New();
marching_cubes->SetValue(0, 127.0f);
marching_cubes->SetInput(threshold->GetOutput()); //(vtkDataObject*)point_cloud);

vtkPolyData* surface = marching_cubes->GetOutput();
marching_cubes->Update(); 

//See That Marching Cubes Worked
cout<<"# Vertices: "<< surface->GetNumberOfVerts()<<endl;
cout<<"# Cells: "<< surface->GetNumberOfCells()<<endl;


//Export (How is this done properly?)
vtkOBJExporter* exporter = vtkOBJExporter::New();
exporter->SetInput(vtkRenderWindow *renWin); //I don't want a render window, I want at file
exporter->SetFilePrefix("/MyPath/surface");
exporter->Write();

Answer 1

您可以使用此类https://github.com/daviddoria/vtkOBJWriter以您期望的方式编写obj文件（与所有其他VTK编写器一样）。不幸的是，vtkOBJExporter还希望编写我从未拥有的其他信息。

vtkMarchingCubes将nifti曲面导出到波前OBJ

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