OrientedCylinder

VTKExamples/Cxx/GeometricObjects/OrientedCylinder


Description

This example illustrates how to create and display a cylinder 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 OrientedArrow. The transform is different because the cylinder height direction is along the y-axis and the arrow height is along the x axis.

Code

OrientedCylinder.cxx

#include <vtkActor.h>
#include <vtkCylinderSource.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 a cylinder.
  // Cylinder height vector is (0,1,0).
  // Cylinder center is in the middle of the cylinder
  vtkSmartPointer<vtkCylinderSource> cylinderSource =
    vtkSmartPointer<vtkCylinderSource>::New();
  cylinderSource->SetResolution(15);

  // 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 (unsigned int 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);   // translate to starting point
  transform->Concatenate(matrix);     // apply direction cosines
  transform->RotateZ(-90.0);          // align cylinder to x axis
  transform->Scale(1.0, length, 1.0); // scale along the height vector
  transform->Translate(0, .5, 0);     // translate to start of cylinder

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

  //Create a mapper and actor for the cylinder
  vtkSmartPointer<vtkPolyDataMapper> mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  vtkSmartPointer<vtkActor> actor =
    vtkSmartPointer<vtkActor>::New();
#ifdef USER_MATRIX
  mapper->SetInputConnection(cylinderSource->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 Cylinder");
  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(OrientedCylinder)

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

add_executable(OrientedCylinder MACOSX_BUNDLE OrientedCylinder.cxx )

target_link_libraries(OrientedCylinder ${VTK_LIBRARIES})

Download and Build OrientedCylinder

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

cd OrientedCylinder/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:

./OrientedCylinder

WINDOWS USERS

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