本文介绍VTK中封闭性检测。
介绍封闭性检测之前，介绍一些基本概念。如果一个网格模型中，一条边只被一个单元包含，那么这条边就是边界边，而边界上的点则为边界点。如果一个模型中含有边界边，则说明该模型不是封闭的，否则是封闭的。 在VTK’中，vtkFeatureEdges是一个非常重要的类，该类能够提取多边形网格模型中四种类型的边。
边界边。非流形边。被三个或者三个以上的多边形单元包含的边即为非流形边。特征边。设置一个特征角的阈值，当包含同一条边的两个三角形的法向量的夹角大于该阈值时，即为一个特征边。流行边。只被两个多边形单元包含的边即为流行边。vtkFeatureEdges的输出是一个包含边信息的vtkPolyData数据。通过判断边界边的数目来确定网格是否封闭。
int numberofopenedges = featureedges->GetOutput()->GetNumberOfCells();们演示用vtkFeatureEdges提取边，并显示出来。
/********************************************************************** Copyright (c) Mr.Bin. All rights reserved. For more information visit: http://blog.csdn.net/webzhuce **********************************************************************/ #include <vtkSmartPointer.h> #include <vtkInformation.h> #include <vtkPolyData.h> #include <vtkRenderWindow.h> #include <vtkRenderWindowInteractor.h> #include <vtkRenderer.h> #include <vtkSelection.h> #include <vtkSelectionNode.h> #include <vtkSphereSource.h> #include <vtkActor.h> #include <vtkCamera.h> #include <vtkProperty.h> #include <vtkIdTypeArray.h> #include <vtkExtractSelection.h> #include <vtkDataSetSurfaceFilter.h> #include <vtkFeatureEdges.h> #include <vtkPolyDataMapper.h> void GenerateData(vtkSmartPointer<vtkPolyData> input) { vtkNew<vtkSphereSource> spheresource; spheresource->Update(); vtkNew<vtkIdTypeArray> ids; ids->SetNumberOfComponents(1); ids->InsertNextValue(2); ids->InsertNextValue(10); vtkNew<vtkSelectionNode> selectionnode; selectionnode->SetFieldType(vtkSelectionNode::CELL); selectionnode->SetContentType(vtkSelectionNode::INDICES); selectionnode->SetSelectionList(ids); selectionnode->GetProperties()->Set(vtkSelectionNode::INVERSE(), 1); vtkNew<vtkSelection> selection; selection->AddNode(selectionnode); vtkNew<vtkExtractSelection> extractselection; extractselection->SetInputData(0, spheresource->GetOutput()); extractselection->SetInputData(1, selection); extractselection->Update(); vtkNew<vtkDataSetSurfaceFilter> surfacefilter; surfacefilter->SetInputConnection(extractselection->GetOutputPort()); surfacefilter->Update(); input->ShallowCopy(surfacefilter->GetOutput()); } int main(int argc, char *argv[]) { vtkNew<vtkPolyData> input; GenerateData(input); vtkNew<vtkFeatureEdges> featureedges; featureedges->SetInputData(input); featureedges->BoundaryEdgesOn(); featureedges->FeatureEdgesOff(); featureedges->ManifoldEdgesOff(); featureedges->NonManifoldEdgesOff(); featureedges->Update(); int numberofopenedges = featureedges->GetOutput()->GetNumberOfCells(); if (numberofopenedges) std::cout << "该网格模型不是封闭的..." << std::endl; else { std::cout << "该网格模型是封闭的..." << std::endl; return EXIT_SUCCESS; } // double leftViewport[4] = { 0.0, 0.0, 0.5, 1.0 }; double rightViewport[4] = { 0.5, 0.0, 1.0, 1.0 }; vtkNew<vtkPolyDataMapper> originalmapper; originalmapper->SetInputData(input); vtkNew<vtkProperty> backfaceprop; backfaceprop->SetDiffuseColor(0.89, 0.81, 0.34); vtkNew<vtkActor> originalactor; originalactor->SetMapper(originalmapper); originalactor->SetBackfaceProperty(backfaceprop); originalactor->GetProperty()->SetDiffuseColor(1.0, 0.3882, 0.2784); vtkNew<vtkPolyDataMapper> edgemapper; edgemapper->SetInputData(featureedges->GetOutput()); vtkNew<vtkActor> edgeactor; edgeactor->SetMapper(edgemapper); edgeactor->GetProperty()->SetEdgeColor(0., 0., 1.0); edgeactor->GetProperty()->SetEdgeVisibility(1); edgeactor->GetProperty()->SetLineWidth(5); vtkNew<vtkRenderer> leftrenderer; leftrenderer->SetViewport(leftViewport); leftrenderer->AddActor(originalactor); leftrenderer->SetBackground(1.0, 1.0, 1.0); vtkNew<vtkRenderer> rightrenderer; rightrenderer->SetViewport(rightViewport); rightrenderer->AddActor(edgeactor); rightrenderer->SetBackground(1.0, 1.0, 1.0); vtkNew<vtkRenderWindow> renderwindow; renderwindow->AddRenderer(leftrenderer); renderwindow->AddRenderer(rightrenderer); renderwindow->SetSize(640, 320); renderwindow->Render(); renderwindow->SetWindowName("FeatureEdges"); vtkNew<vtkRenderWindowInteractor> renderwindowinteractor; renderwindowinteractor->SetRenderWindow(renderwindow); leftrenderer->GetActiveCamera()->SetPosition(0, -1, 0); leftrenderer->GetActiveCamera()->SetFocalPoint(0, 0, 0); leftrenderer->GetActiveCamera()->SetViewUp(0, 0, 1); leftrenderer->GetActiveCamera()->Azimuth(30); leftrenderer->GetActiveCamera()->Elevation(30); leftrenderer->ResetCamera(); rightrenderer->SetActiveCamera(leftrenderer->GetActiveCamera()); renderwindow->Render(); renderwindowinteractor->Start(); return EXIT_SUCCESS; }