CellPicking
VTKExamples/Cxx/Picking/CellPicking
Description
This example demonstrates how to get the coordinates of the point on an actor that is clicked with the left mouse button. It also indicates which cell the selected point belongs to by highlighting the edges of that cell.
Code
CellPicking.cxx
#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkRendererCollection.h>
#include <vtkDataSetMapper.h>
#include <vtkUnstructuredGrid.h>
#include <vtkIdTypeArray.h>
#include <vtkTriangleFilter.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkCommand.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkPolyData.h>
#include <vtkPoints.h>
#include <vtkCellArray.h>
#include <vtkPlaneSource.h>
#include <vtkCellPicker.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkProperty.h>
#include <vtkSelectionNode.h>
#include <vtkSelection.h>
#include <vtkExtractSelection.h>
#include <vtkObjectFactory.h>
// Catch mouse events
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
static MouseInteractorStyle* New();
MouseInteractorStyle()
{
selectedMapper = vtkSmartPointer<vtkDataSetMapper>::New();
selectedActor = vtkSmartPointer<vtkActor>::New();
}
virtual void OnLeftButtonDown()
{
// Get the location of the click (in window coordinates)
int* pos = this->GetInteractor()->GetEventPosition();
vtkSmartPointer<vtkCellPicker> picker =
vtkSmartPointer<vtkCellPicker>::New();
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;
vtkSmartPointer<vtkIdTypeArray> ids =
vtkSmartPointer<vtkIdTypeArray>::New();
ids->SetNumberOfComponents(1);
ids->InsertNextValue(picker->GetCellId());
vtkSmartPointer<vtkSelectionNode> selectionNode =
vtkSmartPointer<vtkSelectionNode>::New();
selectionNode->SetFieldType(vtkSelectionNode::CELL);
selectionNode->SetContentType(vtkSelectionNode::INDICES);
selectionNode->SetSelectionList(ids);
vtkSmartPointer<vtkSelection> selection =
vtkSmartPointer<vtkSelection>::New();
selection->AddNode(selectionNode);
vtkSmartPointer<vtkExtractSelection> extractSelection =
vtkSmartPointer<vtkExtractSelection>::New();
#if VTK_MAJOR_VERSION <= 5
extractSelection->SetInput(0, this->Data);
extractSelection->SetInput(1, selection);
#else
extractSelection->SetInputData(0, this->Data);
extractSelection->SetInputData(1, selection);
#endif
extractSelection->Update();
// In selection
vtkSmartPointer<vtkUnstructuredGrid> selected =
vtkSmartPointer<vtkUnstructuredGrid>::New();
selected->ShallowCopy(extractSelection->GetOutput());
std::cout << "There are " << selected->GetNumberOfPoints()
<< " points in the selection." << std::endl;
std::cout << "There are " << selected->GetNumberOfCells()
<< " cells in the selection." << std::endl;
#if VTK_MAJOR_VERSION <= 5
selectedMapper->SetInputConnection(
selected->GetProducerPort());
#else
selectedMapper->SetInputData(selected);
#endif
selectedActor->SetMapper(selectedMapper);
selectedActor->GetProperty()->EdgeVisibilityOn();
selectedActor->GetProperty()->SetEdgeColor(1,0,0);
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);
int main (int, char *[])
{
vtkSmartPointer<vtkPlaneSource> planeSource =
vtkSmartPointer<vtkPlaneSource>::New();
planeSource->Update();
vtkSmartPointer<vtkTriangleFilter> triangleFilter =
vtkSmartPointer<vtkTriangleFilter>::New();
triangleFilter->SetInputConnection(planeSource->GetOutputPort());
triangleFilter->Update();
vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
mapper->SetInputConnection(triangleFilter->GetOutputPort());
vtkSmartPointer<vtkActor> actor =
vtkSmartPointer<vtkActor>::New();
actor->GetProperty()->SetColor(0,1,0); //green
actor->SetMapper(mapper);
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
renderWindow->AddRenderer(renderer);
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow(renderWindow);
renderWindowInteractor->Initialize();
// Set the custom stype to use for interaction.
vtkSmartPointer<MouseInteractorStyle> style =
vtkSmartPointer<MouseInteractorStyle>::New();
style->SetDefaultRenderer(renderer);
style->Data = triangleFilter->GetOutput();
renderWindowInteractor->SetInteractorStyle(style);
renderer->AddActor(actor);
renderer->ResetCamera();
renderer->SetBackground(0,0,1); // Blue
renderWindow->Render();
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}
CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
PROJECT(CellPicking)
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
add_executable(CellPicking MACOSX_BUNDLE CellPicking.cxx)
target_link_libraries(CellPicking ${VTK_LIBRARIES})
Download and Build CellPicking
Click here to download CellPicking and its CMakeLists.txt file. Once the tarball CellPicking.tar has been downloaded and extracted,
cd CellPicking/build
If VTK is installed:
cmake ..
If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:
cmake -DVTK_DIR:PATH=/home/me/vtk_build ..
Build the project:
make
and run it:
./CellPicking
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.