# TubesWithVaryingRadiusAndColors

Repository source: TubesWithVaryingRadiusAndColors

### Description¶

This example shows how to vary the radius of a tube with one scalar and color the tube with another.

• Contributed by Marcus Thamson

Note

This original source code for this example is here.

Question

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

### Code¶

TubesWithVaryingRadiusAndColors.cxx

#include <math.h>
#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCellArray.h>
#include <vtkDoubleArray.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkMath.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTubeFilter.h>
#include <vtkUnsignedCharArray.h>

int main(int, char*[])
{
vtkNew<vtkNamedColors> nc;

// Spiral tube
unsigned int nV = 256;       // No. of vertices
unsigned int nCyc = 5;       // No. of spiral cycles
double rT1 = 0.1, rT2 = 0.5; // Start/end tube radii
double rS = 2;               // Spiral radius
double h = 10;               // Height
unsigned int nTv = 8;        // No. of surface elements for each tube vertex

// Create points and cells for the helix.
vtkNew<vtkPoints> points;
for (unsigned int i = 0; i < nV; i++)
{
// Helcial coordinates
auto vX = rS * cos(2 * vtkMath::Pi() * nCyc * i / (nV - 1));
auto vY = rS * sin(2 * vtkMath::Pi() * nCyc * i / (nV - 1));
auto vZ = h * i / nV;
points->InsertPoint(i, vX, vY, vZ);
}

vtkNew<vtkCellArray> lines;
lines->InsertNextCell(nV);
for (unsigned int i = 0; i < nV; i++)
{
lines->InsertCellPoint(i);
}

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

// Varying tube radius using sine-function.
vtkNew<vtkDoubleArray> tubeRadius;
tubeRadius->SetName("TubeRadius");
tubeRadius->SetNumberOfTuples(nV);
for (unsigned int i = 0; i < nV; i++)
{
tubeRadius->SetTuple1(
i, rT1 + (rT2 - rT1) * sin(vtkMath::Pi() * i / (nV - 1)));
}
polyData->GetPointData()->AddArray(tubeRadius);
polyData->GetPointData()->SetActiveScalars("TubeRadius");

// RBG array (could add Alpha channel too I guess...).
// Varying from blue to red.
vtkNew<vtkUnsignedCharArray> colors;
colors->SetName("Colors");
colors->SetNumberOfComponents(3);
colors->SetNumberOfTuples(nV);
for (unsigned int i = 0; i < nV; i++)
{
colors->InsertTuple3(i, int(255 * i / (nV - 1)), 0,
int(255 * (nV - 1 - i) / (nV - 1)));
}
polyData->GetPointData()->AddArray(colors);

vtkNew<vtkTubeFilter> tube;
tube->SetInputData(polyData);
tube->SetNumberOfSides(nTv);
tube->SetVaryRadiusToVaryRadiusByAbsoluteScalar();

vtkNew<vtkPolyDataMapper> mapper;
mapper->SetInputConnection(tube->GetOutputPort());
mapper->ScalarVisibilityOn();
mapper->SetScalarModeToUsePointFieldData();
mapper->SelectColorArray("Colors");

vtkNew<vtkActor> actor;
actor->SetMapper(mapper);

vtkNew<vtkRenderer> renderer;
renderer->AddActor(actor);
renderer->SetBackground(nc->GetColor3d("SteelBlue").GetData());

// Make an oblique view.
renderer->GetActiveCamera()->Azimuth(30);
renderer->GetActiveCamera()->Elevation(30);
renderer->ResetCamera();

vtkNew<vtkRenderWindow> renWin;
vtkNew<vtkRenderWindowInteractor> iren;

iren->SetRenderWindow(renWin);
renWin->AddRenderer(renderer);
renWin->SetSize(500, 500);
renWin->Render();
renWin->SetWindowName("TubesWithVaryingRadiusAndColors");

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

iren->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(TubesWithVaryingRadiusAndColors)

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

if (NOT VTK_FOUND)
message(FATAL_ERROR "TubesWithVaryingRadiusAndColors: 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.")
add_executable(TubesWithVaryingRadiusAndColors MACOSX_BUNDLE TubesWithVaryingRadiusAndColors.cxx )
target_link_libraries(TubesWithVaryingRadiusAndColors PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS TubesWithVaryingRadiusAndColors MODULES${VTK_LIBRARIES}
)


### Download and Build TubesWithVaryingRadiusAndColors¶

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

cd TubesWithVaryingRadiusAndColors/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:

./TubesWithVaryingRadiusAndColors


WINDOWS USERS

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