vtkCellPicker 拾取 三角面片

 1.vtkSelectedNode

也可以用于鼠标选择部分，更精确，比画矩形选取；

2.实现方案

CellPickerInteractorStyle类派生于vtkInteraTrackballCamera,并通过重载该函数类的OnLeftButtonDown（）函数来处理鼠标左键消息。PolyData：被拾取模型数据，需要通过外部设置。在响应鼠标左键消息时，首先定义vtkCellPicker对象，使用Pick（）函数实现拾取。拾取完毕后，即可通过GetCellId()函数来得到当前拾取的单元索取号; 可以实现单元格选择；

这里就涉及了vtkPolyData的局部数据提取功能。实现该功能时使用了几个新的类。

• vtkIdTypeArray:对象存储当前选中的单位的索引号，每次只选取一个单元，因此每次该对象仅有一个索引号；
• vtkSelectedNode对象与vtkSelection对象通常搭配使用，vtkSelection实际上是一个vtkSelectionNode的数组，而vtkSelectionNode则声明了要提取的数据的类型，这里SetFiledType()设置数据的类型为单元，SeiContentType()设置数据的内容为索引号。
• vtkExtractSelection:实现了数据提取功能，其第一个输入为被提取的vtkPolyData，第二个输入为vtkSelection对象，标记要提取的数据类型。

提取完毕，即可将提取的结果保存至一个vtkActor对象，并添加至当前的vtkRenderer中显示。

3.效果

 4 code

#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>


// Catch mouse events
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
  static MouseInteractorStyle* New();

  MouseInteractorStyle()
  {
    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());

    double* 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;

      vtkNew<vtkIdTypeArray> ids;
      ids->SetNumberOfComponents(1);
      ids->InsertNextValue(picker->GetCellId());

      vtkNew<vtkSelectionNode> selectionNode;
      selectionNode->SetFieldType(vtkSelectionNode::CELL);
      selectionNode->SetContentType(vtkSelectionNode::INDICES);
      selectionNode->SetSelectionList(ids);

      vtkNew<vtkSelection> selection;
      selection->AddNode(selectionNode);

      vtkNew<vtkExtractSelection> extractSelection;
      extractSelection->SetInputData(0, this->Data);
      extractSelection->SetInputData(1, selection);
      extractSelection->Update();

      // In selection
      vtkNew<vtkUnstructuredGrid> selected;
      selected->ShallowCopy(extractSelection->GetOutput());

      std::cout << "Number of points in the selection: "
        << selected->GetNumberOfPoints() << std::endl;
      std::cout << "Number of cells in the selection : "
        << selected->GetNumberOfCells() << std::endl;
      selectedMapper->SetInputData(selected);
      selectedActor->SetMapper(selectedMapper);
      selectedActor->GetProperty()->EdgeVisibilityOn();
      selectedActor->GetProperty()->SetColor(
        colors->GetColor3d("Tomato").GetData());

      selectedActor->GetProperty()->SetLineWidth(3);

      this->Interactor->GetRenderWindow()
        ->GetRenderers()
        ->GetFirstRenderer()
        ->AddActor(selectedActor);
    }
    // Forward events
    vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
  }

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

vtkStandardNewMacro(MouseInteractorStyle);

 

//vtkSmartPointer <vtkPolyData> ReadStl(char *fileName)
//{
//  vtkSmartPointer<vtkSTLReader> reader = vtkSmartPointer<vtkSTLReader>::New();
//  reader->SetFileName(fileName);
//  reader->Update();
//  vtkSmartPointer <vtkPolyData> poly = reader->GetOutput();
//  return poly;
//}

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

  //vtkNew<vtkPlaneSource> planeSource;
  //planeSource->Update();

  //vtkSmartPointer<vtkXMLPolyDataReader> reader =
  //  vtkSmartPointer<vtkXMLPolyDataReader>::New();
  //reader->SetFileName("./KneeCTFemurSeg.vtp");
  //reader->Update();

  auto polyjg = ReadStl("./soft-Femur.stl");

  //vtkNew<vtkTriangleFilter> triangleFilter;
  triangleFilter->SetInputData
  //triangleFilter->SetInputData(reader->GetOutput());
  //triangleFilter->Update();
    vtkSmartPointer<vtkSphereSource> sphereSource =
          vtkSmartPointer<vtkSphereSource>::New();
    sphereSource->Update();
  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(sphereSource->GetOutputPort());

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

  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  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 = sphereSource->GetOutput();

  renderWindowInteractor->SetInteractorStyle(style);

  renderer->AddActor(actor);
  renderer->ResetCamera();

  renderer->SetBackground(colors->GetColor3d("PaleTurquoise").GetData());

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

  return EXIT_SUCCESS;
}