# WeightedTransformFilter

vtk-examples/Cxx/PolyData/WeightedTransformFilter

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### Code¶

WeightedTransformFilter.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkFloatArray.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointData.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkTransform.h>
#include <vtkTransformFilter.h>
#include <vtkWeightedTransformFilter.h>

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

// Use a sphere as a basis of the shape
vtkNew<vtkSphereSource> sphere;
sphere->SetPhiResolution(40);
sphere->SetThetaResolution(40);
sphere->Update();

vtkPolyData* sphereData = sphere->GetOutput();

// Create a data array to hold the weighting coefficients
vtkNew<vtkFloatArray> tfarray;
vtkIdType npoints = sphereData->GetNumberOfPoints();
tfarray->SetNumberOfComponents(2);
tfarray->SetNumberOfTuples(npoints);

// Parameterize the sphere along the z axis, and fill the weights
// with (1.0-a, a) to linearly interpolate across the shape
for (int i = 0; i < npoints; i++)
{
double pt[3];
sphereData->GetPoint(i, pt);
//    double x = pt[0];
//    double y = pt[1];
double z = pt[2];

double zn = z + 0.5;
double zn1 = 1.0 - zn;
if (zn > 1.0)
{
zn = 1.0;
}
if (zn1 < 0.0)
{
zn1 = 0.0;
}

tfarray->SetComponent(i, 0, zn1);
tfarray->SetComponent(i, 1, zn);
}

// Create field data to hold the array, and bind it to the sphere
//  vtkNew<vtkFieldData> fd;
tfarray->SetName("weights");

// Use an ordinary transform to stretch the shape
vtkNew<vtkTransform> stretch;
stretch->Scale(1, 1, 3.2);

vtkNew<vtkTransformFilter> stretchFilter;
stretchFilter->SetInputData(sphereData);
stretchFilter->SetTransform(stretch);

// Now, for the weighted transform stuff
vtkNew<vtkWeightedTransformFilter> weightedTrans;

// Create two transforms to interpolate between
vtkNew<vtkTransform> identity;
identity->Identity();

vtkNew<vtkTransform> rotated;
double rotatedAngle = 45;
rotated->RotateX(rotatedAngle);

weightedTrans->SetNumberOfTransforms(2);
weightedTrans->SetTransform(identity, 0);
weightedTrans->SetTransform(rotated, 1);
// which data array should the filter use ?
weightedTrans->SetWeightArray("weights");

weightedTrans->SetInputConnection(stretchFilter->GetOutputPort());

vtkNew<vtkPolyDataMapper> weightedTransMapper;
weightedTransMapper->SetInputConnection(weightedTrans->GetOutputPort());
vtkNew<vtkActor> weightedTransActor;
weightedTransActor->SetMapper(weightedTransMapper);
weightedTransActor->GetProperty()->SetDiffuseColor(
colors->GetColor3d("Banana").GetData());
weightedTransActor->GetProperty()->SetRepresentationToSurface();

// Visualize
vtkNew<vtkRenderer> renderer;
vtkNew<vtkRenderWindow> renderWindow;
renderWindow->SetWindowName("WeightedTransformFilter");

vtkNew<vtkRenderWindowInteractor> interactor;
interactor->SetRenderWindow(renderWindow);

renderer->SetBackground(colors->GetColor3d("RoyalBlue").GetData());
renderWindow->SetSize(300, 300);

renderer->ResetCamera();
renderer->GetActiveCamera()->Azimuth(90);
renderer->GetActiveCamera()->Dolly(1);

renderWindow->Render();

interactor->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(WeightedTransformFilter)

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

if (NOT VTK_FOUND)
message(FATAL_ERROR "WeightedTransformFilter: 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(WeightedTransformFilter PRIVATE ${VTK_LIBRARIES} ) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS WeightedTransformFilter MODULES${VTK_LIBRARIES}
)


cd WeightedTransformFilter/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:

./WeightedTransformFilter


WINDOWS USERS

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