# SurfaceFromUnorganizedPointsWithPostProc

VTKExamples/Cxx/Filtering/SurfaceFromUnorganizedPointsWithPostProc

### Description

This example is an extension to the example previously posted at: Create a surface from Unorganized Points

The objective is again to use vtkSurfaceReconstructionFilter to construct a surface from a set of points. However, the direct output of the vtkSurfaceReconstructionFilter does not match with the spatial position of the original point set. Instead, there is a scale change and translation in between. To cure this, in this example we added a post transformation to move the reconstructed surface back to the position of the original points, which in some cases might be more favorable.

### Code

SurfaceFromUnorganizedPointsWithPostProc.cxx

    #include <vtkVersion.h>
    #include <vtkSurfaceReconstructionFilter.h>
    #include <vtkSmartPointer.h>

    #include <vtkNamedColors.h>
    #include <vtkProgrammableSource.h>
    #include <vtkContourFilter.h>
    #include <vtkReverseSense.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkPolyData.h>
    #include <vtkCamera.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkMath.h>
    #include <cmath>

    #include <vtkTransform.h>
    #include <vtkTransformPolyDataFilter.h>

    static void readPoints(vtkPoints* points);

    static vtkSmartPointer<vtkPolyData> transform_back(vtkSmartPointer<vtkPoints> pt, vtkSmartPointer<vtkPolyData> pd);

    int main(int, char *[])
    {
      vtkSmartPointer<vtkNamedColors> namedColors =
        vtkSmartPointer<vtkNamedColors>::New();

      // Read some points
      vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();

      readPoints(points);

      vtkSmartPointer<vtkPolyData> polydata = vtkSmartPointer<vtkPolyData>::New();
      polydata->SetPoints(points);

      // Construct the surface and create isosurface.
      vtkSmartPointer<vtkSurfaceReconstructionFilter> surf =
        vtkSmartPointer<vtkSurfaceReconstructionFilter>::New();

    #if VTK_MAJOR_VERSION <= 5
      surf->SetInput(polydata);
    #else
      surf->SetInputData(polydata);
    #endif

      vtkSmartPointer<vtkContourFilter> contourFilter = vtkSmartPointer<vtkContourFilter>::New();
      contourFilter->SetInputConnection(surf->GetOutputPort());
      contourFilter->SetValue(0, 0.0);

      // Sometimes the contouring algorithm can create a volume whose gradient
      // vector and ordering of polygon (using the right hand rule) are
      // inconsistent. vtkReverseSense cures this problem.
      vtkSmartPointer<vtkReverseSense> reverse = vtkSmartPointer<vtkReverseSense>::New();
      reverse->SetInputConnection(contourFilter->GetOutputPort());
      reverse->ReverseCellsOn();
      reverse->ReverseNormalsOn();
      reverse->Update();

      vtkSmartPointer<vtkPolyData> newSurf = transform_back( points, reverse->GetOutput());

      vtkSmartPointer<vtkPolyDataMapper> map = vtkSmartPointer<vtkPolyDataMapper>::New();
      map->SetInputConnection(reverse->GetOutputPort());
      map->ScalarVisibilityOff();

      vtkSmartPointer<vtkActor> surfaceActor = vtkSmartPointer<vtkActor>::New();
      surfaceActor->SetMapper(map);
      surfaceActor->GetProperty()->SetDiffuseColor(
        namedColors->GetColor3d("Tomato").GetData());
      surfaceActor->GetProperty()->SetSpecularColor(namedColors->GetColor3d("Seashell").GetData());
      surfaceActor->GetProperty()->SetSpecular(.4);
      surfaceActor->GetProperty()->SetSpecularPower(50);

      // Create the RenderWindow, Renderer and both Actors
      vtkSmartPointer<vtkRenderer> ren = vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin = vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren);
      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      // Add the actors to the renderer, set the background and size
      ren->AddActor(surfaceActor);
      ren->SetBackground(namedColors->GetColor3d("Burlywood").GetData());
      renWin->SetSize(400, 400);
      ren->GetActiveCamera()->SetFocalPoint(0, 0, 0);
      ren->GetActiveCamera()->SetPosition(1, 0, 0);
      ren->GetActiveCamera()->SetViewUp(0, 0, 1);
      ren->ResetCamera();
      ren->GetActiveCamera()->Azimuth(20);
      ren->GetActiveCamera()->Elevation(30);
      ren->GetActiveCamera()->Dolly(1.2);
      ren->ResetCameraClippingRange();

      iren->Initialize();
      renWin->Render();
      iren->Start();

      return 0;
    }

    vtkSmartPointer<vtkPolyData> transform_back(vtkSmartPointer<vtkPoints> pt, vtkSmartPointer<vtkPolyData> pd)
    {
      // The reconstructed surface is transformed back to where the
      // original points are. (Hopefully) it is only a similarity
      // transformation.

      // 1. Get bounding box of pt, get its minimum corner (left, bottom, least-z), at c0, pt_bounds

      // 2. Get bounding box of surface pd, get its minimum corner (left, bottom, least-z), at c1, pd_bounds

      // 3. compute scale as:
      //       scale = (pt_bounds[1] - pt_bounds[0])/(pd_bounds[1] - pd_bounds[0]);

      // 4. transform the surface by T := T(pt_bounds[0], [2], [4]).S(scale).T(-pd_bounds[0], -[2], -[4])

      // 1.
      double pt_bounds[6];  // (xmin,xmax, ymin,ymax, zmin,zmax)
      pt->GetBounds(pt_bounds);

      // 2.
      double pd_bounds[6];  // (xmin,xmax, ymin,ymax, zmin,zmax)
      pd->GetBounds(pd_bounds);

    //   // test, make sure it is isotropic
    //   std::cout<<(pt_bounds[1] - pt_bounds[0])/(pd_bounds[1] - pd_bounds[0])<<std::endl;
    //   std::cout<<(pt_bounds[3] - pt_bounds[2])/(pd_bounds[3] - pd_bounds[2])<<std::endl;
    //   std::cout<<(pt_bounds[5] - pt_bounds[4])/(pd_bounds[5] - pd_bounds[4])<<std::endl;
    //   // TEST

      // 3
      double scale = (pt_bounds[1] - pt_bounds[0])/(pd_bounds[1] - pd_bounds[0]);

      // 4.
      vtkSmartPointer<vtkTransform> transp = vtkSmartPointer<vtkTransform>::New();
      transp->Translate(pt_bounds[0], pt_bounds[2], pt_bounds[4]);
      transp->Scale(scale, scale, scale);
      transp->Translate(- pd_bounds[0], - pd_bounds[2], - pd_bounds[4]);

      vtkSmartPointer<vtkTransformPolyDataFilter> tpd = vtkSmartPointer<vtkTransformPolyDataFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      tpd->SetInput(pd);
    #else
      tpd->SetInputData(pd);
    #endif
      tpd->SetTransform(transp);
      tpd->Update();

      return tpd->GetOutput();
    }

    void readPoints(vtkPoints* points)
    {

      float x, y, z;
      // generate random points on unit sphere
      for(int i=0; i<5000; i++)
      {

          double u = vtkMath::Random(0.0,1.0);
          double v = vtkMath::Random(0.0,1.0);
          double phi = 2.0*3.14159265*u;
          double theta = acos(2.0*v-1.0);

          x = std::cos(phi)*std::sin(theta);
          y = std::sin(phi)*std::sin(theta);
          z = std::cos(theta);

          points->InsertNextPoint(x, y, z);
      }

      return;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(SurfaceFromUnorganizedPointsWithPostProc)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(SurfaceFromUnorganizedPointsWithPostProc MACOSX_BUNDLE SurfaceFromUnorganizedPointsWithPostProc.cxx )

    target_link_libraries(SurfaceFromUnorganizedPointsWithPostProc ${VTK_LIBRARIES})

### Download and Build SurfaceFromUnorganizedPointsWithPostProc

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

    cd SurfaceFromUnorganizedPointsWithPostProc/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:

    ./SurfaceFromUnorganizedPointsWithPostProc

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