# EllipticalCylinderDemo

vtk-examples/Cxx/GeometricObjects/EllipticalCylinderDemo

### Description¶

The example shows the vtkPolyLine that forms the base of the elliptical cylinder and an oriented arrow that represents the vector that vtkLinearExtrusionFilter uses to create the cylinder. The example takes an optional triple that defines the vector for the filter. The length of the vector is the height of the cylinder.

Other languages

See (Python)

Question

### Code¶

EllipticalCylinderDemo.cxx

#include <vtkActor.h>
#include <vtkArrowSource.h>
#include <vtkCamera.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkLinearExtrusionFilter.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPoints.h>
#include <vtkPolyDataMapper.h>
#include <vtkPolyLine.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkTubeFilter.h>

int main(int argc, char* argv[])
{
double nx = 0.0;
double ny = 0.0;
double nz = 100.0;

if (argc > 3)
{
nx = atof(argv[1]);
ny = atof(argv[2]);
nz = atof(argv[3]);
}
vtkNew<vtkNamedColors> colors;

double angle = 0;
double r1, r2;
double centerX, centerY;
r1 = 50;
r2 = 30;
centerX = 10.0;
centerY = 5.0;

vtkNew<vtkPoints> points;
int id = 0;
while (angle <= 2.0 * vtkMath::Pi() + (vtkMath::Pi() / 60.0))
{
points->InsertNextPoint(r1 * cos(angle) + centerX,
r2 * sin(angle) + centerY, 0.0);
angle = angle + (vtkMath::Pi() / 60.0);
++id;
}

vtkNew<vtkPolyLine> line;
line->GetPointIds()->SetNumberOfIds(id);
for (unsigned int i = 0; i < static_cast<unsigned int>(id); ++i)
{
line->GetPointIds()->SetId(i, i);
}

vtkNew<vtkCellArray> lines;
lines->InsertNextCell(line);

vtkNew<vtkPolyData> polyData;
polyData->SetPoints(points);
polyData->SetLines(lines);

vtkNew<vtkLinearExtrusionFilter> extrude;
extrude->SetInputData(polyData);
extrude->SetExtrusionTypeToNormalExtrusion();
extrude->SetVector(nx, ny, nz);
extrude->Update();

// Create an oriented arrow
double startPoint[3], endPoint[3];
startPoint[0] = centerX;
startPoint[1] = centerY;
startPoint[2] = 0.0;
for (auto i = 0; i < 3; ++i)
{
endPoint[i] = startPoint[i] + extrude->GetVector()[i];
}

// 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);

vtkNew<vtkMinimalStandardRandomSequence> rng;
rng->SetSeed(8775070);
auto max_r = 10.0;

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

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

// 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
vtkNew<vtkTransform> transform;
transform->Translate(startPoint);
transform->Concatenate(matrix);
transform->Scale(length, length, length);

vtkNew<vtkArrowSource> arrowSource;
arrowSource->SetTipResolution(31);
arrowSource->SetShaftResolution(21);

// Transform the polydata
vtkNew<vtkTransformPolyDataFilter> transformPD;
transformPD->SetTransform(transform);
transformPD->SetInputConnection(arrowSource->GetOutputPort());

// Create a mapper and actor for the arrow
vtkNew<vtkPolyDataMapper> arrowMapper;
arrowMapper->SetInputConnection(transformPD->GetOutputPort());

vtkNew<vtkActor> arrowActor;
arrowActor->SetMapper(arrowMapper);
arrowActor->GetProperty()->SetColor(colors->GetColor3d("Tomato").GetData());

vtkNew<vtkTubeFilter> tubes;
tubes->SetInputData(polyData);
tubes->SetNumberOfSides(21);

vtkNew<vtkPolyDataMapper> lineMapper;
lineMapper->SetInputConnection(tubes->GetOutputPort());

vtkNew<vtkActor> lineActor;
lineActor->SetMapper(lineMapper);
lineActor->GetProperty()->SetColor(colors->GetColor3d("Peacock").GetData());

vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputConnection(extrude->GetOutputPort());

vtkNew<vtkActor> actor;
actor->SetMapper(mapper);
actor->GetProperty()->SetColor(colors->GetColor3d("Banana").GetData());
actor->GetProperty()->SetOpacity(.7);

vtkNew<vtkRenderer> ren;
ren->SetBackground(colors->GetColor3d("SlateGray").GetData());

vtkNew<vtkRenderWindow> renWin;
renWin->SetWindowName("EllipticalCylinderDemo");
renWin->SetSize(600, 600);

vtkNew<vtkRenderWindowInteractor> iren;
iren->SetRenderWindow(renWin);

vtkNew<vtkInteractorStyleTrackballCamera> style;
iren->SetInteractorStyle(style);

vtkNew<vtkCamera> camera;
camera->SetPosition(0, 1, 0);
camera->SetFocalPoint(0, 0, 0);
camera->SetViewUp(0, 0, 1);
camera->Azimuth(30);
camera->Elevation(30);

ren->SetActiveCamera(camera);
ren->ResetCamera();
ren->ResetCameraClippingRange();

renWin->Render();
iren->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(EllipticalCylinderDemo)

find_package(VTK COMPONENTS
CommonColor
CommonCore
CommonDataModel
CommonTransforms
FiltersCore
FiltersGeneral
FiltersModeling
InteractionStyle
RenderingContextOpenGL2
RenderingCore
RenderingFreeType
RenderingGL2PSOpenGL2
RenderingOpenGL2
)

if (NOT VTK_FOUND)
message(FATAL_ERROR "EllipticalCylinderDemo: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
target_link_libraries(EllipticalCylinderDemo PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS EllipticalCylinderDemo MODULES${VTK_LIBRARIES}
)


cd EllipticalCylinderDemo/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:

./EllipticalCylinderDemo


WINDOWS USERS

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