# LandmarkTransform

VTKExamples/Cxx/Filtering/LandmarkTransform

### Description¶

This example creates two point sets which it assumes are known, ordered correspondences. It then transforms Source to Target and displays the matrix used in the transformation.

Question

### Code¶

LandmarkTransform.cxx

#include <vtkPoints.h>
#include <vtkSmartPointer.h>
#include <vtkLandmarkTransform.h>
#include <vtkMatrix4x4.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkVertexGlyphFilter.h>

int main(int, char *[])
{
/*
This demo creates a coordinate frame (+x, +y, +z) of vectors and a rotated,
peturbed frame (+z, +y, -x) and aligns the rotated frame to the original as best as possible.
*/

vtkSmartPointer<vtkPoints> sourcePoints =
vtkSmartPointer<vtkPoints>::New();
double sourcePoint1[3] = {1.0, 0.0, 0.0};
sourcePoints->InsertNextPoint(sourcePoint1);
double sourcePoint2[3] = {0.0, 1.0, 0.0};
sourcePoints->InsertNextPoint(sourcePoint2);
double sourcePoint3[3] = {0.0, 0.0, 1.0};
sourcePoints->InsertNextPoint(sourcePoint3);

vtkSmartPointer<vtkPoints> targetPoints =
vtkSmartPointer<vtkPoints>::New();
double targetPoint1[3] = {0.0, 0.0, 1.1};
targetPoints->InsertNextPoint(targetPoint1);
double targetPoint2[3] = {0.0, 1.02, 0.0};
targetPoints->InsertNextPoint(targetPoint2);
double targetPoint3[3] = {-1.11, 0.0, 0.0};
targetPoints->InsertNextPoint(targetPoint3);

// Setup the transform
vtkSmartPointer<vtkLandmarkTransform> landmarkTransform =
vtkSmartPointer<vtkLandmarkTransform>::New();
landmarkTransform->SetSourceLandmarks(sourcePoints);
landmarkTransform->SetTargetLandmarks(targetPoints);
landmarkTransform->SetModeToRigidBody();
landmarkTransform->Update(); //should this be here?

vtkSmartPointer<vtkPolyData> source =
vtkSmartPointer<vtkPolyData>::New();
source->SetPoints(sourcePoints);

vtkSmartPointer<vtkPolyData> target =
vtkSmartPointer<vtkPolyData>::New();
target->SetPoints(targetPoints);

vtkSmartPointer<vtkVertexGlyphFilter> sourceGlyphFilter =
vtkSmartPointer<vtkVertexGlyphFilter>::New();
sourceGlyphFilter->SetInputData(source);
sourceGlyphFilter->Update();

vtkSmartPointer<vtkVertexGlyphFilter> targetGlyphFilter =
vtkSmartPointer<vtkVertexGlyphFilter>::New();
targetGlyphFilter->SetInputData(target);
targetGlyphFilter->Update();

vtkSmartPointer<vtkTransformPolyDataFilter> transformFilter =
vtkSmartPointer<vtkTransformPolyDataFilter>::New();
transformFilter->SetInputConnection(sourceGlyphFilter->GetOutputPort());
transformFilter->SetTransform(landmarkTransform);
transformFilter->Update();

// Display the transformation matrix that was computed
vtkMatrix4x4* mat = landmarkTransform->GetMatrix();
std::cout << "Matrix: " << *mat << std::endl;

// Visualize
vtkSmartPointer<vtkPolyDataMapper> sourceMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
sourceMapper->SetInputConnection(sourceGlyphFilter->GetOutputPort());

vtkSmartPointer<vtkActor> sourceActor =
vtkSmartPointer<vtkActor>::New();
sourceActor->SetMapper(sourceMapper);
sourceActor->GetProperty()->SetColor(0,1,0);
sourceActor->GetProperty()->SetPointSize(4);

vtkSmartPointer<vtkPolyDataMapper> targetMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
targetMapper->SetInputConnection(targetGlyphFilter->GetOutputPort());

vtkSmartPointer<vtkActor> targetActor =
vtkSmartPointer<vtkActor>::New();
targetActor->SetMapper(targetMapper);
targetActor->GetProperty()->SetColor(1,0,0);
targetActor->GetProperty()->SetPointSize(4);

vtkSmartPointer<vtkPolyDataMapper> solutionMapper =
vtkSmartPointer<vtkPolyDataMapper>::New();
solutionMapper->SetInputConnection(transformFilter->GetOutputPort());

vtkSmartPointer<vtkActor> solutionActor =
vtkSmartPointer<vtkActor>::New();
solutionActor->SetMapper(solutionMapper);
solutionActor->GetProperty()->SetColor(0,0,1);
solutionActor->GetProperty()->SetPointSize(3);

// Create a renderer, render window, and interactor
vtkSmartPointer<vtkRenderer> renderer =
vtkSmartPointer<vtkRenderer>::New();
vtkSmartPointer<vtkRenderWindow> renderWindow =
vtkSmartPointer<vtkRenderWindow>::New();
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow(renderWindow);

// Add the actor to the scene
renderer->SetBackground(.3, .6, .3); // Background color green

// Render and interact
renderWindow->Render();
renderWindowInteractor->Start();

return EXIT_SUCCESS;
}


### CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(LandmarkTransform)

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


cd LandmarkTransform/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:

./LandmarkTransform


WINDOWS USERS

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