VTK學習（十五）封閉性檢測

#include "vtkAutoInit.h" 
VTK_MODULE_INIT(vtkRenderingOpenGL2); // VTK was built with vtkRenderingOpenGL2
VTK_MODULE_INIT(vtkInteractionStyle);

#include <vtkSmartPointer.h>
#include <vtkSelectionNode.h>
#include <vtkInformation.h>
#include <vtkUnstructuredGrid.h>
#include <vtkPolyData.h>
#include <vtkPolyDataNormals.h>
#include <vtkPointData.h>
#include <vtkXMLPolyDataReader.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSelection.h>
#include <vtkSelectionNode.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkProperty.h>
#include <vtkIdTypeArray.h>
#include <vtkExtractSelection.h>
#include <vtkDataSetSurfaceFilter.h>
#include <vtkFeatureEdges.h>
#include <vtkFillHolesFilter.h>

void GenerateData(vtkSmartPointer<vtkPolyData> input)
{
	vtkSmartPointer<vtkSphereSource> sphereSource =
		vtkSmartPointer<vtkSphereSource>::New();
	sphereSource->Update();

	vtkSmartPointer<vtkIdTypeArray> ids =
		vtkSmartPointer<vtkIdTypeArray>::New();
	ids->SetNumberOfComponents(1);
	ids->InsertNextValue(2);
	ids->InsertNextValue(10);

	vtkSmartPointer<vtkSelectionNode> selectionNode =
		vtkSmartPointer<vtkSelectionNode>::New();
	selectionNode->SetFieldType(vtkSelectionNode::CELL);
	selectionNode->SetContentType(vtkSelectionNode::INDICES);
	selectionNode->SetSelectionList(ids);
	selectionNode->GetProperties()->Set(vtkSelectionNode::INVERSE(), 1);

	vtkSmartPointer<vtkSelection> selection =
		vtkSmartPointer<vtkSelection>::New();
	selection->AddNode(selectionNode);

	vtkSmartPointer<vtkExtractSelection> extractSelection =
		vtkSmartPointer<vtkExtractSelection>::New();
	extractSelection->SetInputData(0, sphereSource->GetOutput());
	extractSelection->SetInputData(1, selection);
	extractSelection->Update();

	vtkSmartPointer<vtkDataSetSurfaceFilter> surfaceFilter =
		vtkSmartPointer<vtkDataSetSurfaceFilter>::New();
	surfaceFilter->SetInputConnection(extractSelection->GetOutputPort());
	surfaceFilter->Update();

	input->ShallowCopy(surfaceFilter->GetOutput());
}

int main(int argc, char *argv[])
{
	vtkSmartPointer<vtkPolyData> input =
		vtkSmartPointer<vtkPolyData>::New();
	GenerateData(input);

	vtkSmartPointer<vtkFeatureEdges> featureEdges =
		vtkSmartPointer<vtkFeatureEdges>::New();
	featureEdges->SetInputData(input);
	featureEdges->BoundaryEdgesOn();
	featureEdges->FeatureEdgesOff();
	featureEdges->ManifoldEdgesOff();
	featureEdges->NonManifoldEdgesOff();
	featureEdges->Update();

	int numberOfOpenEdges = featureEdges->GetOutput()->GetNumberOfCells();
	if (numberOfOpenEdges)
	{
		std::cout << "該網格模型不是封閉的..." << std::endl;
	}
	else
	{
		std::cout << "該網格模型是封閉的..." << std::endl;
		return EXIT_SUCCESS;
	}

	vtkSmartPointer<vtkFillHolesFilter> fillHolesFilter =
		vtkSmartPointer<vtkFillHolesFilter>::New();
	fillHolesFilter->SetInputData(input);
	fillHolesFilter->Update();

	vtkSmartPointer<vtkPolyDataNormals> normals =
		vtkSmartPointer<vtkPolyDataNormals>::New();
	normals->SetInputConnection(fillHolesFilter->GetOutputPort());
	normals->ConsistencyOn();
	normals->SplittingOff();
	normals->Update();

	//////////////////////////////////////////////////////////////////////////
	double leftViewport[4] = { 0.0, 0.0, 0.5, 1.0 };
	double rightViewport[4] = { 0.5, 0.0, 1.0, 1.0 };

	vtkSmartPointer<vtkPolyDataMapper> originalMapper =
		vtkSmartPointer<vtkPolyDataMapper>::New();
	originalMapper->SetInputData(input);

	vtkSmartPointer<vtkProperty> backfaceProp =
		vtkSmartPointer<vtkProperty>::New();
	backfaceProp->SetDiffuseColor(0.89, 0.81, 0.34);

	vtkSmartPointer<vtkActor> originalActor =
		vtkSmartPointer<vtkActor>::New();
	originalActor->SetMapper(originalMapper);
	originalActor->SetBackfaceProperty(backfaceProp);
	originalActor->GetProperty()->SetDiffuseColor(1.0, 0.3882, 0.2784);

	vtkSmartPointer<vtkPolyDataMapper> edgeMapper =
		vtkSmartPointer<vtkPolyDataMapper>::New();
	edgeMapper->SetInputData(featureEdges->GetOutput());
	vtkSmartPointer<vtkActor> edgeActor =
		vtkSmartPointer<vtkActor>::New();
	edgeActor->SetMapper(edgeMapper);
	edgeActor->GetProperty()->SetEdgeColor(0., 0., 1.0);
	edgeActor->GetProperty()->SetEdgeVisibility(1);
	edgeActor->GetProperty()->SetLineWidth(5);

	vtkSmartPointer<vtkPolyDataMapper> filledMapper =
		vtkSmartPointer<vtkPolyDataMapper>::New();
	filledMapper->SetInputData(normals->GetOutput());

	vtkSmartPointer<vtkActor> filledActor =
		vtkSmartPointer<vtkActor>::New();
	filledActor->SetMapper(filledMapper);
	filledActor->GetProperty()->SetDiffuseColor(1.0, 0.3882, 0.2784);

	vtkSmartPointer<vtkRenderer> leftRenderer =
		vtkSmartPointer<vtkRenderer>::New();
	leftRenderer->SetViewport(leftViewport);
	leftRenderer->AddActor(originalActor);
	leftRenderer->AddActor(edgeActor);
	leftRenderer->SetBackground(1.0, 1.0, 1.0);

	vtkSmartPointer<vtkRenderer> rightRenderer =
		vtkSmartPointer<vtkRenderer>::New();
	rightRenderer->SetViewport(rightViewport);
	rightRenderer->AddActor(filledActor);
	rightRenderer->SetBackground(1.0, 1.0, 1.0);

	vtkSmartPointer<vtkRenderWindow> renderWindow =
		vtkSmartPointer<vtkRenderWindow>::New();
	renderWindow->AddRenderer(leftRenderer);
	renderWindow->AddRenderer(rightRenderer);
	renderWindow->SetSize(640, 320);
	renderWindow->Render();
	renderWindow->SetWindowName("PolyDataClosed");

	vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
		vtkSmartPointer<vtkRenderWindowInteractor>::New();
	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;
}

如果一個邊只被一個多邊形包含，那麼這條邊就是邊界邊。是否存在邊界邊是檢測一個網格模型是否封閉的重要特徵。

vtkFeatureEdges是一個非常重要的類，該類能夠提取多邊形網格模型中四種類型的邊

1.邊界邊，就是隻被一個多邊形包含的邊

2.非流行邊，被三個或者三個以上的多邊形包含的邊即爲四種類型的邊

3.特徵邊，當包含同一條邊的兩個三角形的法向量的夾角大於該閾值時，即爲特徵邊。

4.流行邊，只爲兩個多邊形包含的邊

vtkSmartPointer<vtkFeatureEdges> featureEdges =
		vtkSmartPointer<vtkFeatureEdges>::New();
	featureEdges->SetInputData(input);
	featureEdges->BoundaryEdgesOn();
	featureEdges->FeatureEdgesOff();
	featureEdges->ManifoldEdgesOff();
	featureEdges->NonManifoldEdgesOff();
	featureEdges->Update();

可以通過邊界邊的數目來確定網格是否封閉

int numberOfOpenEdges = featureEdges->GetOutput()->GetNumberOfCells();

可以用vtkFillHolesFiller來進行漏洞填補。首先檢測出網格中所有的邊界邊，然後找出這些邊界邊的每一個閉合迴路，最後將閉合迴路進行三角化，實現填補目的。

vtkSmartPointer<vtkPolyDataNormals> normals =
		vtkSmartPointer<vtkPolyDataNormals>::New();
	normals->SetInputConnection(fillHolesFilter->GetOutputPort());
	normals->ConsistencyOn();
	normals->SplittingOff();
	normals->Update();