VTK 三维模型的简单拾取交互_vtk 获取三维切面上任意点

最近需要对stl三维模型表面的点进行拾取，然后也需要点云配准，所以之前都是把stl转成pcd，用pcl瞎搞。pcl里也也能实现对点云的点拾取，但是pcl的viewer显示点云没有光源（PCL小白，不知道能不能设置，我是没找到的），这就看不到三维模型的表面特征了（我要根据表面特征手动选点）。网上看到的资料都是用VTK，就研究一下（VTK小白中的小白，有不对的地方请谅解）。

先贴参考：
https://blog.csdn.net/qq_42570058/article/details/107914377：看完可以对vtk有个大概的了解

https://blog.csdn.net/webzhuce/article/details/72802322：了解一下vtk里的拾取类

https://blog.csdn.net/shenziheng1/article/details/54959201：三维模型点拾取，但是对于复杂的三维模型，可能会拾取错误（即选到了背面的点，这里仔细看了vtkPointPicker的描述，拾取错误的原因应该是是背面的点离射线更近，想象一下射线重三角面片中穿过）上面是我个人的理解，不知道对不对。

https://blog.csdn.net/asimov_liu/article/details/78748785：拾取点/显示当前点选点并删除上次的点选点

https://blog.csdn.net/q610098308/article/details/125421795：拾取三角面片。这里我们可以参考使用vtkCellPicker，就应该可以避免选到背面了（我的理解是射线碰到三角面片直接返回信息）。

然后参考上面拾取三角面片的例子，我们这里不显示三角面片，用一个球代替显示，达到所谓的点拾取。这了我读的是vtk文件，stl得加个头文件

 #include <vtkSTLReader.h>
 
  vtkSmartPointer<vtkSTLReader> reader = vtkSmartPointer<vtkSTLReader>::New();
  reader->SetFileName("1.stl");
  reader->Update();

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#include "vtkAutoInit.h"
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);

VTK_MODULE_INIT(vtkRenderingVolumeOpenGL2);
VTK_MODULE_INIT(vtkRenderingFreeType);


#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkCellPicker.h>
#include <vtkSelectionNode.h>
#include <vtkSelection.h>
#include <vtkRendererCollection.h>
#include <vtkExtractSelection.h>
#include <vtkObjectFactory.h>
#include <vtkNamedColors.h>
#include <vtkUnstructuredGrid.h>
#include <vtkNamedColors.h>
#include <vtkPolyDataReader.h>

// Catch mouse events
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
	//double picked[3];//选取的点坐标
	double* worldPosition;
	static MouseInteractorStyle* New();

	MouseInteractorStyle()
	{
		last_picked_actor = NULL;
		selectedMapper = vtkSmartPointer<vtkDataSetMapper>::New();
		selectedActor = vtkSmartPointer<vtkActor>::New();
	}

	virtual void OnLeftButtonDown() override
	{
		vtkNew<vtkNamedColors> colors;

		// Get the location of the click (in window coordinates)
		int* pos = this->GetInteractor()->GetEventPosition();

		vtkNew<vtkCellPicker> picker;
		picker->SetTolerance(0.0005);

		// Pick from this location.
		picker->Pick(pos[0], pos[1], 0, this->GetDefaultRenderer());

		worldPosition = picker->GetPickPosition();
		std::cout << "Cell id is: " << picker->GetCellId() << std::endl;


		
		if (picker->GetCellId() != -1)
		{
			std::cout << "Pick position is: (" << worldPosition[0] << ", "<< worldPosition[1] << ", " << worldPosition[2] << ")" << endl;
			//如果之前选择了其他点，删除上一次的标记点
			if (this->last_picked_actor)
			{
				this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer()->RemoveActor(last_picked_actor);
				//last_picked_actor->Delete();
				//last_picked_actor=vtkActor::New();
			}

			//获取此次的标记点
			this->last_picked_actor = GetActor();

			if (this->last_picked_actor)
			{
				//标记出来，
				this->last_picked_actor->SetScale(2.0);
				this->last_picked_actor->GetProperty()->SetColor(1.0, 0.0, 0.0);
				this->Interactor->GetRenderWindow()->GetRenderers()->GetFirstRenderer()->AddActor(this->last_picked_actor);
			}
			
		}
		// Forward events
		vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
	}

	vtkSmartPointer<vtkPolyData> Data;
	vtkSmartPointer<vtkDataSetMapper> selectedMapper;
	vtkSmartPointer<vtkActor> selectedActor;

private:
	vtkActor* last_picked_actor;

	inline vtkActor* GetActor()
	{

		vtkSmartPointer<vtkSphereSource> sphereSource =
			vtkSmartPointer<vtkSphereSource>::New();
		sphereSource->Update();

		vtkSmartPointer<vtkPolyDataMapper> mapper =
			vtkSmartPointer<vtkPolyDataMapper>::New();
		mapper->SetInputConnection(sphereSource->GetOutputPort());
		vtkActor* actor = vtkActor::New();
		actor->SetMapper(mapper);
		actor->SetPosition(worldPosition);
		return actor;
	}

};

vtkStandardNewMacro(MouseInteractorStyle);


int main(int, char* [])
{
	vtkNew<vtkNamedColors> colors;

	vtkSmartPointer<vtkPolyDataReader> reader = vtkSmartPointer<vtkPolyDataReader>::New();
	reader->SetFileName("Mesh.vtk");
	reader->Update();

	vtkNew<vtkPolyDataMapper> mapper;
	mapper->SetInputConnection(reader->GetOutputPort());

	vtkNew<vtkActor> actor;
	actor->GetProperty()->SetColor(colors->GetColor3d("SeaGreen").GetData());
	actor->SetMapper(mapper);

	vtkNew<vtkRenderer> renderer;
	renderer->AddActor(actor);
	renderer->ResetCamera();
	renderer->SetBackground(colors->GetColor3d("PaleTurquoise").GetData());

	vtkNew<vtkRenderWindow> renderWindow;
	renderWindow->Render();
	renderWindow->AddRenderer(renderer);
	renderWindow->SetWindowName("CellPicking");

	vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
	renderWindowInteractor->SetRenderWindow(renderWindow);
	renderWindowInteractor->Initialize();

	// Set the custom stype to use for interaction.
	vtkNew<MouseInteractorStyle> style;
	style->SetDefaultRenderer(renderer);
	style->Data = reader->GetOutput();

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

	return EXIT_SUCCESS;
}
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补充-----------2024.1.16---------------
使用QT+VTK显示时，导入自定义交互后，关闭qt主窗口后，程序仍在运行问题：

		//VTK交互器
		vtkNew<vtkRenderWindowInteractor> interactor;
		interactor->SetRenderWindow(renderWindow);
		// 设置交互器样式
		vtkNew<vtkMyInteractorStyle_Single_point_pickup> style;
		style->SetDefaultRenderer(renderer);
		//导入自定义交互
		interactor->SetInteractorStyle(style);
		interactor->Initialize();
		interactor->Start();
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Start()后应该是会启动一个线程进行循环。在关闭qt主窗口后，这个交互器的循环仍在执行，导致整个程序仍在运行。

解决：在qt窗口关闭时执行以下程序（即退出自定义交互的循环

	if (interactor) interactor->ExitCallback();
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