VTK9.2.0+Qt5.14.0 绘制点云

背景

为了显示结构光重建后的点云，开发QT5.14.0+VTK9.2.0的上位机软件，用于对结构光3D相机进行控制，并接收传输回来的3D数据，显示在窗口中。

配置QT和VTK

VTK9.2.0下载源码，用Cmake编译，编译好的VTK9.2.0-vs2017在链接中：VTK9.2.0-vs2017编译工程

QT5.14.0下载链接
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VTK绘制点云

VTK构造显示数据的基本流程是：
Point -> Cell -> Poly -> PolyMapper -> Actor -> Renderer -> QVTKOpenGLNativeWidget
其中，
$\cdot$ vtkPoints类对应创建点数据，包含点的坐标，以及属性
$\cdot$ vtkCellArray类是构造一种元素，比如三角网格，对应有三个point，那么一个cell中就会存储这三个point的索引值
$\cdot$ vtkPolyData类是构造多边形元素
$\cdot$ vtkActor类是构造“演员”
$\cdot$ vtkRenderer类是构造着色器，理解为渲染场景的控制，包含“演员”、光源、背景等
$\cdot$ vtkPolyDataMapper类将多边形元素和Actor建立联系
$\cdot$ QVTKOpenGLNativeWidget类是渲染窗口控件
在qt中创建VTK渲染窗口控件有两种方式：
① 双击工程左侧.ui文件，在qt designer中创建ui.openGLWidget对象
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ui.openGLWidget是通过qt designer，拖入QVTKWidget控件，右键该控件选择“提升窗口部件”，基类选择QOpenGLWidget, 提升的类名称为QVTKOpenGLNativeWidget, 在右上角的对象查看器中，重命名为openGLWidget. (注意：VTK8的创建方式是不一样的，注意版本)

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② 方法二是直接用代码生成的方式，在工程的构造函数中直接new一个QVTKOpenGLNativeWidget对象，并设置其位置信息

QVtkDemo2::QVtkDemo2(QWidget *parent)
    : QMainWindow(parent)
{
    ui.setupUi(this);
    //new一个QVTKOpenGLNativeWidget的对象
	ui.openGLWidget = new QVTKOpenGLNativeWidget(this);
	//设置渲染窗口的尺寸
	ui.openGLWidget->resize(100, 100); 
	 //设置左上角的在主窗口中的坐标
	ui.openGLWidget->move(50, 50);
	testVtk3D();
}

构造一个testVtk3D函数，用于绘制点云，并使用vtkCameraOrientationWidget类创建一个坐标轴对象，由于testVtk3D在构造函数中调用，需要在头文件中将其定义为全局变量。另外，VTK使用的是智能指针vtkSmartPointer，无需管理其释放问题，VTK还提供vtkNew类的智能指针，
vtkSmartPointer与vtkNew两者主要的使用区别在于：前者多用于全局变量，后者多用于局部变量

	//在头文件中定义为全局变量
	vtkSmartPointer<vtkCameraOrientationWidget> cameraOrientationWidget;

void QVtkDemo2::testVtk3D()
{
	//创建着色器对象
	vtkSmartPointer<vtkRenderer> g_vtkRenderer = vtkSmartPointer<vtkRenderer>::New();
	//设置背景颜色
	g_vtkRenderer->SetBackground(.1, .2, .4);
	//创建point对象
	vtkSmartPointer<vtkPoints> g_vtkPoints = vtkSmartPointer<vtkPoints>::New();
	//创建cell对象
	vtkSmartPointer<vtkCellArray> g_vtkVertices = vtkSmartPointer<vtkCellArray>::New();
	vtkIdType id[1];
	//随机生成200个点
	for (int i = 0; i < 200; i++)
	{
		float x = rand() % 10;
		float y = rand() % 10;
		float z = rand() % 10;
		id[0] = g_vtkPoints->InsertNextPoint(x, y, z);
		g_vtkVertices->InsertNextCell(1, id);
	}
	//创建poly对象
	vtkSmartPointer<vtkPolyData> g_vtkpolyData = vtkSmartPointer<vtkPolyData>::New();
	g_vtkpolyData->SetPoints(g_vtkPoints);
	g_vtkpolyData->SetVerts(g_vtkVertices);
	//创建polyMapper
	vtkSmartPointer<vtkPolyDataMapper> g_vtkpointsMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
	g_vtkpointsMapper->SetInputData(g_vtkpolyData);
	//创建Actor
	vtkSmartPointer<vtkActor> g_vtkpointsActor = vtkSmartPointer<vtkActor>::New();
	g_vtkpointsActor->SetMapper(g_vtkpointsMapper);
	g_vtkpointsActor->GetProperty()->SetPointSize(3);//设置点的大小
	g_vtkRenderer->AddActor(g_vtkpointsActor);
	//根据点云的包围盒，寻找最佳的显示视点位置
	g_vtkRenderer->ResetCamera();
	//ui中的绘制窗口添加定义的着色器
	ui.openGLWidget->renderWindow()->AddRenderer(g_vtkRenderer);
	//开始三维渲染
	ui.openGLWidget->renderWindow()->Render();

	//绘制坐标轴
	cameraOrientationWidget = vtkSmartPointer<vtkCameraOrientationWidget>::New();
	cameraOrientationWidget->SetInteractor(ui.openGLWidget->interactor());
	cameraOrientationWidget->SetParentRenderer(g_vtkRenderer);
	cameraOrientationWidget->SetEnabled(1);

	return;
}

运行效果如下图
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VTK根据Z值绘制点云颜色

void QVtkDemo2::testVtk3D()
{
	//创建着色器对象
	vtkSmartPointer<vtkRenderer> g_vtkRenderer = vtkSmartPointer<vtkRenderer>::New();
	//设置背景颜色
	g_vtkRenderer->SetBackground(.1, .2, .4);
	//创建point对象
	vtkSmartPointer<vtkPoints> g_vtkPoints = vtkSmartPointer<vtkPoints>::New();
	g_vtkPoints->SetNumberOfPoints(200);
	//创建cell对象
	vtkSmartPointer<vtkCellArray> g_vtkVertices = vtkSmartPointer<vtkCellArray>::New();
	vtkIdType id[1];
	//随机生成200个点
	float minz = VTK_FLOAT_MAX, maxz = VTK_FLOAT_MIN;
	for (int i = 0; i < 200; i++)
	{
		float x = rand() % 10;
		float y = rand() % 10;
		float z = rand() % 10;
		//提前申请了points的数量，使用set比insert速度更快
		g_vtkPoints->SetPoint(i, x, y, z);
		id[0] = i;
		g_vtkVertices->InsertNextCell(1, id);
		if (z > maxz)
		{
			maxz = z;
		}
		if (z < minz)
		{
			minz = z;
		}
	}
	//创建poly对象
	vtkSmartPointer<vtkPolyData> g_vtkpolyData = vtkSmartPointer<vtkPolyData>::New();
	g_vtkpolyData->SetPoints(g_vtkPoints);
	g_vtkpolyData->SetVerts(g_vtkVertices);

	vtkSmartPointer<vtkVertexGlyphFilter> g_glyphFilter = vtkSmartPointer<vtkVertexGlyphFilter>::New();
	g_glyphFilter->SetInputData(g_vtkpolyData);
	g_glyphFilter->Update();

	vtkSmartPointer<vtkElevationFilter> g_elevationFilter = vtkSmartPointer<vtkElevationFilter>::New();
	g_elevationFilter->SetInputConnection(g_glyphFilter->GetOutputPort());
	g_elevationFilter->SetLowPoint(0, 0, minz);
	g_elevationFilter->SetHighPoint(0, 0, maxz);

	//创建polyMapper
	vtkSmartPointer<vtkPolyDataMapper> g_vtkpointsMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
	g_vtkpointsMapper->SetInputConnection(g_elevationFilter->GetOutputPort());

	//创建Actor
	vtkSmartPointer<vtkActor> g_vtkpointsActor = vtkSmartPointer<vtkActor>::New();
	g_vtkpointsActor->SetMapper(g_vtkpointsMapper);
	g_vtkpointsActor->GetProperty()->SetPointSize(3);//设置点的大小
	g_vtkRenderer->AddActor(g_vtkpointsActor);

	//建立查找表，将Z深度映射为一个查找表，表的值对应不同的颜色
	vtkNew<vtkLookupTable> lut = vtkNew<vtkLookupTable>::vtkNew();
	lut->SetNumberOfTableValues(7);
	lut->SetHueRange(0.0, 0.67); //这里是红到蓝，设置<0.67,1>为蓝到红
	lut->SetTableRange(minz, maxz);
	lut->Build();
	
	//创建色谱栏
	vtkNew<vtkScalarBarActor> colorBar = vtkNew<vtkScalarBarActor>::vtkNew();
	colorBar->SetLookupTable(lut);
	colorBar->SetNumberOfLabels(7);
	colorBar->SetBarRatio(0.10);
	colorBar->SetUnconstrainedFontSize(0.05);
	colorBar->SetMaximumHeightInPixels(100);
	colorBar->SetDisplayPosition(500, 80);
	g_vtkRenderer->AddActor2D(colorBar);

	//根据点云的包围盒，寻找最佳的显示视点位置
	g_vtkRenderer->ResetCamera();
	//ui中的绘制窗口添加定义的着色器
	ui.openGLWidget->renderWindow()->AddRenderer(g_vtkRenderer);
	//开始三维渲染
	ui.openGLWidget->renderWindow()->Render();

	//绘制坐标轴
	cameraOrientationWidget = vtkSmartPointer<vtkCameraOrientationWidget>::New();
	cameraOrientationWidget->SetInteractor(ui.openGLWidget->interactor());
	cameraOrientationWidget->SetParentRenderer(g_vtkRenderer);
	cameraOrientationWidget->SetEnabled(1);

	return;
}

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VTK赋予点云真实纹理信息（灰度\彩色）

这个功能的需要，是因为重建点云是一个“白模”或像上一节中的深度颜色映射图一样，有时候会需要点云贴上相机拍摄的灰度纹理或彩色纹理。下面的代码中，我定义了vtkUnsignedCharArray的指针，对256个点，分别赋予了一个颜色，R=G=B的情况就是灰度。由此，可实现点云真实纹理的显示。

void QVtkDemo2::testVtk3D()
{
	//创建着色器对象
	vtkSmartPointer<vtkRenderer> g_vtkRenderer = vtkSmartPointer<vtkRenderer>::New();
	//设置背景颜色
	g_vtkRenderer->SetBackground(.1, .2, .4);
	//创建point对象
	vtkSmartPointer<vtkPoints> g_vtkPoints = vtkSmartPointer<vtkPoints>::New();
	g_vtkPoints->SetNumberOfPoints(256);
	//创建cell对象
	vtkSmartPointer<vtkCellArray> g_vtkVertices = vtkSmartPointer<vtkCellArray>::New();
	vtkIdType id[1];

	vtkSmartPointer<vtkUnsignedCharArray> ptColor = vtkSmartPointer<vtkUnsignedCharArray>::New();
	ptColor->SetNumberOfTuples(256);
	ptColor->SetNumberOfComponents(3);
	//随机生成256个点, 每个点一个灰度值
	float minz = VTK_FLOAT_MAX, maxz = VTK_FLOAT_MIN;
	for (int i = 0; i < 256; i++)
	{
		float x = rand() % 10;
		float y = rand() % 10;
		float z = rand() % 10;
		//提前申请了points的数量，使用set比insert速度更快
		g_vtkPoints->SetPoint(i, x, y, z);
		id[0] = i;
		g_vtkVertices->InsertNextCell(1, id);
		//赋予每一个点一个RGB值，R=G=B显示灰度，根据需要修改程序
		unsigned char rgb[3];
		rgb[0] = i;
		rgb[1] = i;
		rgb[2] = i;
		ptColor->InsertTypedTuple(i, rgb);
	}
	

	//创建poly对象
	vtkSmartPointer<vtkPolyData> g_vtkpolyData = vtkSmartPointer<vtkPolyData>::New();
	g_vtkpolyData->SetPoints(g_vtkPoints);
	g_vtkpolyData->SetVerts(g_vtkVertices);
	g_vtkpolyData->GetPointData()->SetScalars(ptColor);

	//创建polyMapper
	vtkSmartPointer<vtkPolyDataMapper> g_vtkpointsMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
	g_vtkpointsMapper->SetInputData(g_vtkpolyData);

	//创建Actor
	vtkSmartPointer<vtkActor> g_vtkpointsActor = vtkSmartPointer<vtkActor>::New();
	g_vtkpointsActor->SetMapper(g_vtkpointsMapper);
	g_vtkpointsActor->GetProperty()->SetPointSize(3);//设置点的大小
	g_vtkRenderer->AddActor(g_vtkpointsActor);

	//根据点云的包围盒，寻找最佳的显示视点位置
	g_vtkRenderer->ResetCamera();
	//ui中的绘制窗口添加定义的着色器
	ui.openGLWidget->renderWindow()->AddRenderer(g_vtkRenderer);
	//开始三维渲染
	ui.openGLWidget->renderWindow()->Render();

	//绘制坐标轴
	cameraOrientationWidget = vtkSmartPointer<vtkCameraOrientationWidget>::New();
	cameraOrientationWidget->SetInteractor(ui.openGLWidget->interactor());
	cameraOrientationWidget->SetParentRenderer(g_vtkRenderer);
	cameraOrientationWidget->SetEnabled(1);

	return;
}