[Vtk] Registration - Landmark Transform

예제 : http://www.vtk.org/Wiki/VTK/Examples/Cxx/Filters/LandmarkTransform

Landmark를 가지고 있는 경우 source -> target으로 정합한 매트릭스를 반환한다.

void myLandmarkTransform(vtkSmartPointer<vtkPolyData> source, vtkSmartPointer<vtkPolyData> target)

{

      vtkSmartPointer<vtkLandmarkTransform> landmarkTransform = vtkSmartPointer<vtkLandmarkTransform>::New();

      landmarkTransform->SetSourceLandmarks(source->GetPoints());

      landmarkTransform->SetTargetLandmarks(target->GetPoints());

      landmarkTransform->SetModeToRigidBody(); // 형태를 유지한다;

      landmarkTransform->Update();

      vtkSmartPointer<vtkTransformPolyDataFilter> transformFilter = vtkSmartPointer<vtkTransformPolyDataFilter>::New();

      transformFilter->SetInputData(source);

      transformFilter->SetTransform(landmarkTransform);

      transformFilter->Update();

      vtkMatrix4x4* mat = landmarkTransform->GetMatrix();

      std::cout << "Matrix: " << *mat << std::endl;

      source->ShallowCopy(transformFilter->GetOutput());

}

vtkLandmarkTransform 의 사용법은 간단하다.

이동을 시킬 vtkPoints 를 SetSourceLandmarks 에 넣고

정합 대산인 vtkPoints 를 SetTargetLandmarks 에 넣는다.

모드를 설정한 뒤 Update() 를 호출한다. 정합 모드는 VTK_LANDMARK_SIMILARITY 가 기본 값이다.

vtkLandmarkTransform은 3가지의 모드가 있다.

landmarkTransform->SetModeToRigidBody() : rotation and traslation only

landmarkTransform->SetModeToSimilarity() : rotation and traslation and isotropic scaling (default)

landmarkTransform->SetModeToAffine()

- 정합 전 (source : white, target : red)

 

- 정합 후

 

정합 후 결과 확인을 위한 Sample Code (두 Polydata의 점이 완전히 쌍을 이루는 경우)

double calculateDistanceBetweenPoints(vtkSmartPointer<vtkPoints> p0, vtkSmartPointer<vtkPoints> p1)

{

      double totalDistance = 0;

      double averageDistance = 0;

      if (p0->GetNumberOfPoints() == p1->GetNumberOfPoints() && p0->GetNumberOfPoints() != 0)

      {

            int numPoints = p0->GetNumberOfPoints();

            double squaredDistance;

            for (int i = 0; i < numPoints; i++)

            {

                  squaredDistance = vtkMath::Distance2BetweenPoints(p0->GetPoint(i), p1->GetPoint(i));

                  totalDistance += sqrt(squaredDistance);

            }

            averageDistance = totalDistance / numPoints;

      }

      return averageDistance;

}