OrientedArrow

VTKExamples/Cxx/GeometricObjects/OrientedArrow


Description

This example illustrates how to create and display an arrow that passes through two points.

It demonstrates two different ways to apply the transform:

  1. Use vtkTransformPolyDataFilter to create a new transformed polydata. This method is useful if the transformed polydata is needed later in the pipeline, e.g. vtkGlyph3DFilter.

  2. Apply the transform directly to the actor using vtkProp3D's SetUserMatrix. No new data is produced.

Switch between the two methods by #defining USER_MATRIX or leaving out the #define.

See

also Compare this example with OrientedCylinder. The transform is different because the cylinder height direction is along the y-axis and the arrow height is along the x axis.

Code

OrientedArrow.cxx

#include <vtkActor.h>
#include <vtkArrowSource.h>
#include <vtkMath.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>

#include <array>

#define USER_MATRIX

int main(int, char *[])
{
  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  // Set the background color.
  std::array<unsigned char , 4> bkg{{26, 51, 77, 255}};
    colors->SetColor("BkgColor", bkg.data());

  //Create an arrow.
  vtkSmartPointer<vtkArrowSource> arrowSource =
    vtkSmartPointer<vtkArrowSource>::New();

  // Generate a random start and end point
  double startPoint[3];
  double endPoint[3];
  vtkSmartPointer<vtkMinimalStandardRandomSequence> rng =
    vtkSmartPointer<vtkMinimalStandardRandomSequence>::New();
  rng->SetSeed(8775070); // For testing.
  for (auto i = 0; i < 3; ++i)
  {
    rng->Next();
    startPoint[i] = rng->GetRangeValue(-10, 10);
    rng->Next();
    endPoint[i] = rng->GetRangeValue(-10, 10);
  }

  // Compute a basis
  double normalizedX[3];
  double normalizedY[3];
  double normalizedZ[3];

  // The X axis is a vector from start to end
  vtkMath::Subtract(endPoint, startPoint, normalizedX);
  double length = vtkMath::Norm(normalizedX);
  vtkMath::Normalize(normalizedX);

  // The Z axis is an arbitrary vector cross X
  double arbitrary[3];
  for (auto i = 0; i < 3; ++i)
  {
    rng->Next();
    arbitrary[i] = rng->GetRangeValue(-10, 10);
  }
  vtkMath::Cross(normalizedX, arbitrary, normalizedZ);
  vtkMath::Normalize(normalizedZ);

  // The Y axis is Z cross X
  vtkMath::Cross(normalizedZ, normalizedX, normalizedY);
  vtkSmartPointer<vtkMatrix4x4> matrix =
    vtkSmartPointer<vtkMatrix4x4>::New();

  // Create the direction cosine matrix
  matrix->Identity();
  for (auto i = 0; i < 3; i++)
  {
    matrix->SetElement(i, 0, normalizedX[i]);
    matrix->SetElement(i, 1, normalizedY[i]);
    matrix->SetElement(i, 2, normalizedZ[i]);
  }

  // Apply the transforms
  vtkSmartPointer<vtkTransform> transform =
    vtkSmartPointer<vtkTransform>::New();
  transform->Translate(startPoint);
  transform->Concatenate(matrix);
  transform->Scale(length, length, length);

  // Transform the polydata
  vtkSmartPointer<vtkTransformPolyDataFilter> transformPD =
    vtkSmartPointer<vtkTransformPolyDataFilter>::New();
  transformPD->SetTransform(transform);
  transformPD->SetInputConnection(arrowSource->GetOutputPort());

  //Create a mapper and actor for the arrow
  vtkSmartPointer<vtkPolyDataMapper> mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  vtkSmartPointer<vtkActor> actor =
    vtkSmartPointer<vtkActor>::New();
#ifdef USER_MATRIX
  mapper->SetInputConnection(arrowSource->GetOutputPort());
  actor->SetUserMatrix(transform->GetMatrix());
#else
  mapper->SetInputConnection(transformPD->GetOutputPort());
#endif
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("Cyan").GetData());

  // Create spheres for start and end point
  vtkSmartPointer<vtkSphereSource> sphereStartSource =
    vtkSmartPointer<vtkSphereSource>::New();
    sphereStartSource->SetCenter(startPoint);
    sphereStartSource->SetRadius(0.8);
  vtkSmartPointer<vtkPolyDataMapper> sphereStartMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  sphereStartMapper->SetInputConnection(sphereStartSource->GetOutputPort());
  vtkSmartPointer<vtkActor> sphereStart =
    vtkSmartPointer<vtkActor>::New();
  sphereStart->SetMapper(sphereStartMapper);
  sphereStart->GetProperty()->SetColor(colors->GetColor3d("Yellow").GetData());

  vtkSmartPointer<vtkSphereSource> sphereEndSource =
    vtkSmartPointer<vtkSphereSource>::New();
    sphereEndSource->SetCenter(endPoint);
    sphereEndSource->SetRadius(0.8);
  vtkSmartPointer<vtkPolyDataMapper> sphereEndMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  sphereEndMapper->SetInputConnection(sphereEndSource->GetOutputPort());
  vtkSmartPointer<vtkActor> sphereEnd =
    vtkSmartPointer<vtkActor>::New();
  sphereEnd->SetMapper(sphereEndMapper);
  sphereEnd->GetProperty()->SetColor(colors->GetColor3d("Magenta").GetData());

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

  //Add the actor to the scene
  renderer->AddActor(actor);
  renderer->AddActor(sphereStart);
  renderer->AddActor(sphereEnd);
  renderer->SetBackground(colors->GetColor3d("BkgColor").GetData());

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

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)

PROJECT(OrientedArrow)

find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(OrientedArrow MACOSX_BUNDLE OrientedArrow.cxx )

target_link_libraries(OrientedArrow ${VTK_LIBRARIES})

Download and Build OrientedArrow

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

cd OrientedArrow/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:

./OrientedArrow

WINDOWS USERS

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