VTK study notes five

Pick up

• Picking is used to select objects in the scene and obtain information about the objects
• Usually call vtkAbstractPicker::Pick() method to pick up the object
• Different picking subclasses return different picking information, such as the object's global coordinates, unit ID, point ID, etc.
• Calling syntax: Pick (SelectX, SelectY, SelectZ, Renderer)
• The characters associated with the Renderer are all picked objects
• The Pick method cannot be called directly, but is managed by the interactive class vtkRenderWindowInteractor

Main picking subcategories

Pickup	effect	return value
vtkWorldPointPicker	Quickly pick up the characters in the scene	Returns the world coordinate value of the picked point
vtkAbstractPropPicker	Pick up objects in the scene	Returns the data type of the picked object
vtkPropPicker：vtkAbstractPropPicker	Pickup operation for hardware support	–
vtkPicker：vtkAbstractPropPicker	Use software to realize boundary picking	–
vtkCellPicker：vtkPicker	Information used to pick up the unit	Return unit ID, parameter coordinates
vtkPointPicker：vtkPicker	Used to get point information	Return the ID and coordinates of the point
vtkAssemblyPath	To access every object in vtkAssembly	Returns the node and transformation matrix of each object

Use pick objects in interactive subclasses to meet user-defined interactive picking operations

	//构建一个vtkCellPicker的实例
	vtkSmartPointer<vtkCellPicker> cellPicker = vtkSmartPointer<vtkCellPicker>::New();

	//构建vtk内建的交互类对象
	vtkSmartPointer<vtkRenderWindowInteractor> iren = vtkSmartPointer<vtkRenderWindowInteractor>::New();
	//将pick对象交由交互类vtkRenderWindowInteractor进行管理
	iren->SetPicker(cellPicker);
	//将绘制窗口对象与绘制交互类绑定
	iren->SetRenderWindow(renWin);


	vtkSmartPointer<MyPointPickerInteractorStyle> style = vtkSmartPointer<MyPointPickerInteractorStyle>::New();
	iren->SetInteractorStyle(style);

class MyPointPickerInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
	static MyPointPickerInteractorStyle* New();
	vtkTypeMacro(MyPointPickerInteractorStyle, vtkInteractorStyleTrackballCamera);

	virtual void OnLeftButtonDown()
	{
		vtkRenderWindowInteractor *rwi = this->Interactor;

		auto render = rwi->GetRenderWindow()->GetRenderers()->GetFirstRenderer();
		double screenPoint[3];
		screenPoint[0] = rwi->GetEventPosition()[0];
		screenPoint[1] = rwi->GetEventPosition()[1];
		screenPoint[2] = rwi->GetEventPosition()[2];

		auto detailPicker = (vtkCellPicker*)(this->Interactor->GetPicker());
		vtkIdType pointId = 0;
		if (detailPicker->Pick(screenPoint[0], screenPoint[1], 0, render))
		{
			vtkIdType cellID = detailPicker->GetCellId();
			pointId = detailPicker->GetPointId();
		}
	}
};
vtkStandardNewMacro(MyPointPickerInteractorStyle);

VTK coordinate system

!(C:\Users\qiang.shen\Downloads\VTK-8.2.0\jpg picture\picture three_VTK coordinate conversion.JPG)

• vtk supports many different types of coordinate systems
• vtk uses the class vtkCoordinate to transform in different coordinate systems

Mainly involved coordinate system

Coordinate System	meaning	Remarks
DISPLAY	The origin is at the lower left corner of the window, and the x/y length is the pixel value of the width and height of the window	–
NORMALIZED DISPLAY	The origin is in the lower left corner of the window, and the length of x/y is 0~1	–
VIEWPORT	A window can be divided into multiple viewports, the lower left corner of each viewport is the origin, and the x/y length is the pixel value of the viewport width and height	–
NORMALIZED VIEWPORT	A window can be divided into multiple viewports, the lower left corner of each viewport is the origin, and the x/y length is 0~1	–
VIEWPORT	A window can be divided into multiple viewports, the lower left corner of each viewport is the origin, and the x/y length is the pixel value of the viewport width and height	–
NORMALIZED VIEWPORT	A window can be divided into multiple viewports, the lower left corner of each viewport is the origin, and the x/y length is 0~1	–
VIEW	Clipping coordinate system in camera space, xyz is -1~1, z direction is depth	–
WORLD	Unified global time coordinate system, xyz is the global actual length	–
MODEL	The coordinate system used when defining the model, usually a local Cartesian coordinate system	–

A demo using vtkCoordinate

#include <vtkSmartPointer.h>
#include <vtkCoordinate.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>

int main(int, char *[])
{
	vtkSmartPointer<vtkRenderWindow> rendererWindow = vtkSmartPointer<vtkRenderWindow>::New();
	rendererWindow->SetSize(400, 400);

	vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
	rendererWindow->AddRenderer(renderer);
	rendererWindow->Render();

	vtkSmartPointer<vtkCoordinate> coordinate = vtkSmartPointer<vtkCoordinate>::New();
	//设置当前的坐标系为归一化的屏幕坐标系
	coordinate->SetCoordinateSystemToNormalizedDisplay();
	//设置当前的坐标系为屏幕坐标系
	//coordinate->SetCoordinateSystemToDisplay();
	//设置当前的坐标系为视口坐标系
	//coordinate->SetCoordinateSystemToViewport();
	//设置当前的坐标系为归一化视口坐标系
	//coordinate->SetCoordinateSystemToNormalizedViewport();
	//设置当前的坐标系为裁剪坐标系
	//coordinate->SetCoordinateSystemToView();
	//设置当前的坐标系为世界坐标系
	//coordinate->SetCoordinateSystemToWorld()



	//取当前坐标系下的一个坐标(0.5, 0,5, 0)
	coordinate->SetValue(0.5, 0.5, 0);
	std::cout << *coordinate << std::endl;
	std::cout << coordinate->GetCoordinateSystemAsString() << std::endl;

	int* val;
	//将设定的坐标转换为屏幕坐标
	val = coordinate->GetComputedDisplayValue(renderer);
	std::cout << "Val: " << val[0] << " " << val[1] << std::endl;

	getchar();
	return EXIT_SUCCESS;
}

vtkActor2D

Express two-dimensional graphics and perform operations on two-dimensional graphics. In the following example, draw discrete two-dimensional point graphics

#include <vtkSmartPointer.h>
#include <vtkCubeSource.h>
#include <vtkPolyData.h>
#include <vtkPoints.h>
#include <vtkVertexGlyphFilter.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkActor2D.h>
#include <vtkPolyDataMapper2D.h>
#include <vtkProperty2D.h>

int main(int, char *[])
{
	vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
	points->InsertNextPoint(10,10,0);
	points->InsertNextPoint(100,100,0);
	points->InsertNextPoint(200,200,0);

	vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();
	polydata->SetPoints(points);

	vtkSmartPointer<vtkVertexGlyphFilter> glyphFilter = vtkSmartPointer<vtkVertexGlyphFilter>::New();
	glyphFilter->SetInputData(polydata);
	glyphFilter->Update();

	vtkSmartPointer<vtkPolyDataMapper2D> mapper = vtkSmartPointer<vtkPolyDataMapper2D>::New();
	mapper->SetInputConnection(glyphFilter->GetOutputPort());
	mapper->Update();

	vtkSmartPointer<vtkActor2D> actor = vtkSmartPointer<vtkActor2D>::New();
	actor->SetMapper(mapper);

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

	// Add the actor to the scene
	renderer->AddActor(actor);
	renderWindow->SetSize(300,300);
	actor->GetProperty()->SetColor(0,1,0);
	actor->GetProperty()->SetPointSize(3);

	// Render and interact
	renderWindow->Render();
	renderWindowInteractor->Start();

	return EXIT_SUCCESS;
}

Annotation

Plane annotation

Put the text on the two-dimensional graphics window, the text will not change due to the user's operation

#include "vtkSmartPointer.h"
#include "vtkSphereSource.h"
#include "vtkPolyDataMapper.h"
#include "vtkActor.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkTextProperty.h"
#include "vtkTextActor.h"
#include "vtkTextMapper.h"
#include "vtkPolyDataMapper2D.h"
#include "vtkAutoInit.h"
#include "vtkScaledTextActor.h"

int main()
{
	VTK_MODULE_INIT(vtkRenderingFreeType)

	//建立文本属性对象
	vtkSmartPointer<vtkTextProperty> pTexProper = vtkSmartPointer<vtkTextProperty>::New();
	pTexProper->SetColor(0 , 0 , 1);
	pTexProper->SetFontSize(18);
	pTexProper->SetFontSize(18);
	pTexProper->SetFontFamily(0);
	pTexProper->SetJustification(1);
	pTexProper->SetBold(1);
	pTexProper->SetItalic(1);
	pTexProper->SetShadow(1);

	//建立文本映射器对象
	//vtkTextMapper : public vtkMapper2D
	vtkSmartPointer<vtkTextMapper> pTexMap = vtkSmartPointer<vtkTextMapper>::New();
	//pTexMap->SetInput("This is a sphere");
	pTexMap->SetTextProperty(pTexProper);

	//vtkSmartPointer<vtkPolyDataMapper2D> pp = vtkPolyDataMapper2D::SafeDownCast(pTexMap);

	vtkSmartPointer<vtkScaledTextActor> textActor = vtkSmartPointer<vtkScaledTextActor>::New();
	//vtkSmartPointer<vtkTextActor> textActor = vtkSmartPointer<vtkTextActor>::New();
	//SetMapper(vtkMapper2D)为私有方法
	textActor->SetInput("This is a sphere");
	//textActor->SetMapper(pTexMap);//设置文本属性有问题
	textActor->SetHeight(0.1);

	//设置字体显示的位置
	textActor->SetPosition(0 , 0);


	//创建三维球体
	vtkSmartPointer<vtkSphereSource> sphere = vtkSmartPointer<vtkSphereSource>::New();

	vtkSmartPointer<vtkPolyDataMapper> sphereMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
	sphereMapper->SetInputConnection(sphere->GetOutputPort());

	vtkSmartPointer<vtkActor> sphereActor = vtkSmartPointer<vtkActor>::New();
	sphereActor->SetMapper(sphereMapper);

	vtkSmartPointer<vtkRenderer> ren = vtkSmartPointer<vtkRenderer>::New();
	ren->AddActor(sphereActor);
	ren->AddActor(textActor);

	vtkSmartPointer<vtkRenderWindow> win = vtkSmartPointer<vtkRenderWindow>::New();
	win->AddRenderer(ren);

	vtkSmartPointer<vtkRenderWindowInteractor> iren = vtkSmartPointer<vtkRenderWindowInteractor>::New();
	iren->SetRenderWindow(win);

	win->Render();
	iren->Start();


	getchar();
	return 0;
}

3D annotation

Add text to the generated 3D graphics, or display text directly in the form of 3D graphics

• Three-dimensional annotation is to use vtkVectorText to create annotation content text
• vtkFollower is a way to draw 3D annotations

	//建立3D 文本，为多边形数据
	vtkSmartPointer<vtkVectorText> atext = vtkSmartPointer<vtkVectorText>::New();
	atext->SetText("Origin");

	//映射文本，注意映射器的类型
	vtkSmartPointer<vtkPolyDataMapper> textMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
	textMapper->SetInputConnection(atext->GetOutputPort());
	vtkSmartPointer<vtkFollower> textActor = vtkSmartPointer<vtkFollower>::New();
	textActor->SetMapper(textMapper);
	textActor->SetPosition(0 , -0.1 , 0);
	textActor->SetScale(0.2 , 0.2 , 0.2);