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ContourWidget

vtk-examples/Cxx/Widgets/ContourWidget


Description

This example generates a set of points which lie on a circle, and the contour through these points. This contour can be interactively warped/modified by dragging the control points.

Other languages

See (Python)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

ContourWidget.cxx

#include <vtkCellArray.h>
#include <vtkContourWidget.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkMath.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkOrientedGlyphContourRepresentation.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

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

  // Create the contour widget
  vtkNew<vtkContourWidget> contourWidget;

  // Override the default representation for the contour widget to customize its
  // look
  vtkNew<vtkOrientedGlyphContourRepresentation> contourRepresentation;
  contourRepresentation->GetLinesProperty()->SetColor(
      colors->GetColor3d("Red").GetData());
  contourWidget->SetRepresentation(contourRepresentation);

  // Generate a set of points arranged in a circle
  int numPts = 10;
  vtkNew<vtkPoints> points;
  for (int i = 0; i < numPts; i++)
  {
    // Create numPts points evenly spread around a circumference of radius 0.1
    const double angle = 2.0 * vtkMath::Pi() * i / numPts;
    points->InsertPoint(static_cast<vtkIdType>(i), 0.1 * cos(angle),
                        0.1 * sin(angle), 0.0);
  }

  // Create a cell array to connect the points into meaningful geometry
  vtkIdType* vertexIndices = new vtkIdType[numPts + 1];
  for (int i = 0; i < numPts; i++)
  {
    vertexIndices[i] = static_cast<vtkIdType>(i);
  }
  // Set the last vertex to 0; this means the last line segment will join the
  // 19th point (vertices[19]) with the first one (vertices[0]), thus closing
  // the circle.
  vertexIndices[numPts] = 0;
  vtkNew<vtkCellArray> lines;
  lines->InsertNextCell(numPts + 1, vertexIndices);

  // Create polydata to hold the geometry just created, and populate it
  vtkNew<vtkPolyData> polydata;
  polydata->SetPoints(points);
  polydata->SetLines(lines);

  // Create the renderer to visualize the scene
  vtkNew<vtkRenderer> renderer;
  renderer->SetBackground(colors->GetColor3d("MidnightBlue").GetData());

  // Create the GUI window to hold the rendered scene
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("ContourWidget");
  renderWindow->SetSize(600, 600);

  // Create the events manager for the renderer window
  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

  // Use the "trackball camera" interactor style, rather than the default
  // "joystick camera"
  vtkNew<vtkInteractorStyleTrackballCamera> style;
  interactor->SetInteractorStyle(style);

  // Set up the contour widget within the visualization pipeline just assembled
  contourWidget->SetInteractor(interactor);
  contourWidget->On(); // Turn on the interactor observer
  contourWidget->Initialize(polydata);
  renderer->ResetCamera(); // Reposition camera to fit the scene elements

  // Start the interaction
  renderWindow->Render();
  interactor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ContourWidget)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkInteractionStyle
  vtkInteractionWidgets
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping ContourWidget: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(ContourWidget MACOSX_BUNDLE ContourWidget.cxx )
  target_link_libraries(ContourWidget PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ContourWidget MACOSX_BUNDLE ContourWidget.cxx )
  target_link_libraries(ContourWidget PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ContourWidget
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build ContourWidget

Click here to download ContourWidget and its CMakeLists.txt file. Once the tarball ContourWidget.tar has been downloaded and extracted,

cd ContourWidget/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:

./ContourWidget

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.