计算图形中心线¶
原理 http://lantiga.github.com/media/AntigaPhDThesis.pdf
把模型封闭，选取输入输出点，依次求内切球，圆心为中心线。
/*!
* \brief 计算中心线
*/
vtkSmartPointer<vtkPolyData> MatUtil::ComputingCenterLines(
vtkSmartPointer<vtkPolyData> surface) {
// 表面整理
vtkNew<vtkCleanPolyData> surface_cleaner;
surface_cleaner->SetInputData(surface);
surface_cleaner->Update();
// 三角形相交检查
vtkNew<vtkTriangleFilter> surface_triangulator;
surface_triangulator->SetInputConnection(surface_cleaner->GetOutputPort());
surface_triangulator->PassLinesOff();
surface_triangulator->PassVertsOff();
surface_triangulator->Update();
vtkSmartPointer<vtkPolyData> centerline_input_surface =
surface_triangulator->GetOutput();
vtkSmartPointer<vtkIdList> cap_center_ids = nullptr;
vtkSmartPointer<vtkvmtkCapPolyData> surface_capper;
// 表面封闭
surface_capper = vtkSmartPointer<vtkvmtkCapPolyData>::New();
surface_capper->SetInputConnection(surface_triangulator->GetOutputPort());
surface_capper->SetDisplacement(0);
surface_capper->SetInPlaneDisplacement(0);
surface_capper->Update();
centerline_input_surface = surface_capper->GetOutput();
cap_center_ids = surface_capper->GetCapCenterIds();
vtkNew<vtkIdList> inlet_seed_ids, outlet_seed_ids;
inlet_seed_ids->InsertNextId(0);
outlet_seed_ids->InsertNextId(1);
// 计算中心线
vtkNew<vtkvmtkPolyDataCenterlines> centerline_filter;
centerline_filter->SetInputData(centerline_input_surface);
centerline_filter->SetCapCenterIds(cap_center_ids);
centerline_filter->SetSourceSeedIds(inlet_seed_ids);
centerline_filter->SetTargetSeedIds(outlet_seed_ids);
centerline_filter->SetRadiusArrayName("MaximumInscribedSphereRadius");
// centerline_filter->SetCostFunction("1/R");
centerline_filter->SetFlipNormals(0);
centerline_filter->SetAppendEndPointsToCenterlines(1);
centerline_filter->SetSimplifyVoronoi(0);
centerline_filter->SetCenterlineResampling(0);
centerline_filter->SetResamplingStepLength(1);
centerline_filter->Update();
return centerline_filter->GetOutput();
}
上边这段程序只适用于管状模型（两个口，分别为入口和出口，不存在交叉），如果模型有多个出入口则需要更改
vtkNew< vtkIdList > inlet_seed_ids, outlet_seed_ids;，自行设计选择器，确定输入输出端口。
**vtkvmtkPolyDataCenterlines**需要把模型打散，根据入口挨个寻找内切球，效率比较低。20M左右的管状模型提取中心线大概50s左右。为了提高效率可以先对模型进行压缩，用压缩后模型找中心线，再跟压缩前模型融合浏览。