VTK笔记——提取边界(vtkFeatureEdges)

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vtkFeatureEdges，VTK的一个类，用于边界提取。
提取的边界包括：
1)边界(boundary)，只被一个多边形使用的边，或者直线单元；
2)非流行(non-manifold)，被三个以上的多边形共用的边；
3)特征边(feature edges)，被两个三角形使用且二面角大于特征角的边；
4)流行边(manifold edges)，只被两个多边形使用的边。

常用于

1)提取模型的边界

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vtkSmartPointer<vtkFeatureEdges> boundaryEdges =
	vtkSmartPointer<vtkFeatureEdges>::New();
boundaryEdges->SetInputConnection(diskSource->GetOutputPort());
boundaryEdges->BoundaryEdgesOn();
boundaryEdges->FeatureEdgesOff();
boundaryEdges->ManifoldEdgesOff();
boundaryEdges->NonManifoldEdgesOff();
boundaryEdges->Update();

注意：提取出来的边界点是无序的，可以用vtkCleanPolyData使其变得有序：

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vtkSmartPointer<vtkStripper> stripper =
	vtkSmartPointer<vtkStripper>::New();
stripper->SetInputConnection(featureEdges->GetOutputPort());
stripper->JoinContiguousSegmentsOn();

vtkSmartPointer<vtkCleanPolyData> cleanPolyData =
	vtkSmartPointer<vtkCleanPolyData>::New();
cleanPolyData->SetInputConnection(stripper->GetOutputPort());
cleanPolyData->Update();

2)检测模型是否闭合

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vtkSmartPointer<vtkFeatureEdges> closedSurface =
	vtkSmartPointer<vtkFeatureEdges>::New();
closedSurface->SetInputConnection(diskSource->GetOutputPort());
closedSurface->FeatureEdgesOff();
closedSurface->BoundaryEdgesOn();
closedSurface->NonManifoldEdgesOn();
closedSurface->Update();
int numberOfOpenEdges = closedSurface->GetOutput()->GetNumberOfCells();
if (numberOfOpenEdges > 0)
{
	std::cout << "Surface is not closed" << std::endl;
}
else
{
	std::cout << "Surface is closed" << std::endl;
}

完整代码

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#include <vtkSmartPointer.h>
#include <vtkFeatureEdges.h>
#include <vtkPolyData.h>
#include <vtkDiskSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>

int main(int, char *[])
{
	vtkSmartPointer<vtkDiskSource> diskSource =
		vtkSmartPointer<vtkDiskSource>::New();
	diskSource->Update();

	vtkSmartPointer<vtkFeatureEdges> boundaryEdges =
		vtkSmartPointer<vtkFeatureEdges>::New();
	boundaryEdges->SetInputConnection(diskSource->GetOutputPort());
	boundaryEdges->BoundaryEdgesOn();
	boundaryEdges->FeatureEdgesOff();
	boundaryEdges->ManifoldEdgesOff();
	boundaryEdges->NonManifoldEdgesOff();
	boundaryEdges->Update();

	vtkSmartPointer<vtkFeatureEdges> closedSurface =
		vtkSmartPointer<vtkFeatureEdges>::New();
	closedSurface->SetInputConnection(diskSource->GetOutputPort());
	closedSurface->FeatureEdgesOff();
	closedSurface->BoundaryEdgesOn();
	closedSurface->NonManifoldEdgesOn();
	closedSurface->Update();
	int numberOfOpenEdges = closedSurface->GetOutput()->GetNumberOfCells();
	if (numberOfOpenEdges > 0)
	{
		std::cout << "Surface is not closed" << std::endl;
	}
	else
	{
		std::cout << "Surface is closed" << std::endl;
	}

	// Visualize
	vtkSmartPointer<vtkPolyDataMapper> edgeMapper =
		vtkSmartPointer<vtkPolyDataMapper>::New();
	edgeMapper->SetInputConnection(boundaryEdges->GetOutputPort());
	vtkSmartPointer<vtkActor> edgeActor =
		vtkSmartPointer<vtkActor>::New();
	edgeActor->SetMapper(edgeMapper);

	vtkSmartPointer<vtkPolyDataMapper> diskMapper =
		vtkSmartPointer<vtkPolyDataMapper>::New();
	diskMapper->SetInputConnection(diskSource->GetOutputPort());
	vtkSmartPointer<vtkActor> diskActor =
		vtkSmartPointer<vtkActor>::New();
	diskActor->SetMapper(diskMapper);

	// Create a renderer, render window, and interactor
	vtkSmartPointer<vtkRenderer> renderer =
		vtkSmartPointer<vtkRenderer>::New();
	vtkSmartPointer<vtkRenderWindow> renderWindow =
		vtkSmartPointer<vtkRenderWindow>::New();
	renderWindow->SetSize(400, 400);
	renderWindow->AddRenderer(renderer);
	vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
		vtkSmartPointer<vtkRenderWindowInteractor>::New();
	renderWindowInteractor->SetRenderWindow(renderWindow);

	renderer->AddActor(edgeActor);
	renderer->AddActor(diskActor);
	renderer->SetBackground(.3, .6, .3); // Background color green

	renderWindow->Render();
	renderWindowInteractor->Start();

	return EXIT_SUCCESS;
}

Ref

vtkFeatureEdges Class Reference
BoundaryEdges
ClosedSurface

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