# ExponentialCosine

VTKExamples/Cxx/VisualizationAlgorithms/ExponentialCosine

### Description¶

Visualization of an exponential cosine function. Function values are indicated by surface displacement. Colors indicate derivative values.

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See (Python)

Question

### Code¶

ExponentialCosine.cxx

//
// Brute force computation of Bessel functions. Might be better to create a
// filter (or source) object. Might also consider vtkSampleFunction.

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkDoubleArray.h>
#include <vtkNamedColors.h>
#include <vtkPlaneSource.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkWarpScalar.h>

int main(int, char*[])
{

auto colors =
vtkSmartPointer<vtkNamedColors>::New();

auto ren =
vtkSmartPointer<vtkRenderer>::New();
auto renWin =
vtkSmartPointer<vtkRenderWindow>::New();

auto iren =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
iren->SetRenderWindow(renWin);

// create plane to warp
auto plane =
vtkSmartPointer<vtkPlaneSource>::New();
plane->SetResolution(300, 300);

auto transform =
vtkSmartPointer<vtkTransform>::New();
transform->Scale(10.0, 10.0, 1.0);

auto transF =
vtkSmartPointer<vtkTransformPolyDataFilter>::New();
transF->SetInputConnection(plane->GetOutputPort());
transF->SetTransform(transform);
transF->Update();

// compute Bessel function and derivatives. This portion could be
// encapsulated into source or filter object.
//
auto input = transF->GetOutput();
auto numPts = input->GetNumberOfPoints();

auto newPts =
vtkSmartPointer<vtkPoints>::New();
newPts->SetNumberOfPoints(numPts);

auto derivs =
vtkSmartPointer<vtkDoubleArray>::New();
derivs->SetNumberOfTuples(numPts);

auto bessel =
vtkSmartPointer<vtkPolyData>::New();
bessel->CopyStructure(input);
bessel->SetPoints(newPts);
bessel->GetPointData()->SetScalars(derivs);

double x[3];

for (auto i = 0; i < numPts; i++)
{
input->GetPoint(i, x);
auto r = sqrt(static_cast<double>(x[0] * x[0]) + x[1] * x[1]);
x[2] = exp(-r) * cos(10.0 * r);
newPts->SetPoint(i, x);
auto deriv = -exp(-r) * (cos(10.0 * r) + 10.0 * sin(10.0 * r));
derivs->SetValue(i, deriv);
}

// warp plane
auto warp =
vtkSmartPointer<vtkWarpScalar>::New();
warp->SetInputData(bessel);
warp->XYPlaneOn();
warp->SetScaleFactor(0.5);

// mapper and actor
auto mapper =
vtkSmartPointer<vtkDataSetMapper>::New();
mapper->SetInputConnection(warp->GetOutputPort());
double tmp[2];
bessel->GetScalarRange(tmp);
mapper->SetScalarRange(tmp[0], tmp[1]);

auto carpet =
vtkSmartPointer<vtkActor>::New();
carpet->SetMapper(mapper);

// assign our actor to the renderer
ren->SetBackground(colors->GetColor3d("Beige").GetData());
renWin->SetSize(640, 480);

// draw the resulting scene
ren->ResetCamera();
ren->GetActiveCamera()->Zoom(1.4);
ren->GetActiveCamera()->Elevation(-55);
ren->GetActiveCamera()->Azimuth(25);
ren->ResetCameraClippingRange();
renWin->Render();

iren->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ExponentialCosine)

find_package(VTK COMPONENTS
vtkCommonColor
vtkCommonCore
vtkCommonDataModel
vtkCommonTransforms
vtkFiltersGeneral
vtkInteractionStyle
vtkRenderingContextOpenGL2
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingGL2PSOpenGL2
vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
message("Skipping ExponentialCosine: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(ExponentialCosine MACOSX_BUNDLE ExponentialCosine.cxx ) target_link_libraries(ExponentialCosine PRIVATE${VTK_LIBRARIES})
else ()
# include all components
target_link_libraries(ExponentialCosine PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS ExponentialCosine MODULES${VTK_LIBRARIES}
)
endif ()


cd ExponentialCosine/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:

./ExponentialCosine


WINDOWS USERS

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