# TransformOrderDemo

VTKExamples/Cxx/PolyData/TransformOrderDemo

### Description

This example creates an image. In the left viewport, it translates the image, then translates and rotates the image. In the right viewport, it rotates the image, then rotates and translates the image. One can see that the result is clearly not the same!

### Code

TransformOrderDemo.cxx

    #include <vtkSmartPointer.h>
    #include <vtkTransform.h>
    #include <vtkAxesActor.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkImageMandelbrotSource.h>
    #include <vtkImageActor.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageCast.h>

    int main(int, char *[])
    {
      // Create an image
      vtkSmartPointer<vtkImageMandelbrotSource> source =
        vtkSmartPointer<vtkImageMandelbrotSource>::New();
      source->Update();

      vtkSmartPointer<vtkImageCast> castFilter =
        vtkSmartPointer<vtkImageCast>::New();
      castFilter->SetInputConnection(source->GetOutputPort());
      castFilter->SetOutputScalarTypeToUnsignedChar();
      castFilter->Update();

      // Create an actor
      vtkSmartPointer<vtkImageActor> actor1a =
        vtkSmartPointer<vtkImageActor>::New();
      actor1a->GetMapper()->SetInputConnection(castFilter->GetOutputPort());
      vtkSmartPointer<vtkImageActor> actor1b =
        vtkSmartPointer<vtkImageActor>::New();
      actor1b->GetMapper()->SetInputConnection(castFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> actor2a =
        vtkSmartPointer<vtkImageActor>::New();
      actor2a->GetMapper()->SetInputConnection(castFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> actor2b =
        vtkSmartPointer<vtkImageActor>::New();
      actor2b->GetMapper()->SetInputConnection(castFilter->GetOutputPort());

      // Create the transformation
      vtkSmartPointer<vtkTransform> transform1a =
        vtkSmartPointer<vtkTransform>::New();
      transform1a->PostMultiply();
      transform1a->Translate(10.0, 0.0, 0.0);
      actor1a->SetUserTransform(transform1a);

      vtkSmartPointer<vtkTransform> transform1b =
        vtkSmartPointer<vtkTransform>::New();
      transform1b->PostMultiply();
      transform1b->Translate(10.0, 0.0, 0.0);
      transform1b->RotateZ(40.0);
      actor1b->SetUserTransform(transform1b);

      vtkSmartPointer<vtkTransform> transform2a =
        vtkSmartPointer<vtkTransform>::New();
      transform2a->PostMultiply();
      transform2a->RotateZ(40.0);
      actor2a->SetUserTransform(transform2a);

      vtkSmartPointer<vtkTransform> transform2b =
        vtkSmartPointer<vtkTransform>::New();
      transform2b->PostMultiply();
      transform2b->RotateZ(40.0);
      transform2b->Translate(10.0, 0.0, 0.0);
      actor2b->SetUserTransform(transform2b);

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double leftViewport[4] = {0.0, 0.0, 0.5, 1.0};
      double rightViewport[4] = {0.5, 0.0, 1.0, 1.0};

      // Cetup render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();

      // Setup both renderers
      vtkSmartPointer<vtkRenderer> leftRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderWindow->AddRenderer(leftRenderer);
      leftRenderer->SetViewport(leftViewport);
      leftRenderer->SetBackground(.6, .5, .4);

      vtkSmartPointer<vtkRenderer> rightRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderWindow->AddRenderer(rightRenderer);
      rightRenderer->SetViewport(rightViewport);
      rightRenderer->SetBackground(.4, .5, .6);

      // an interactor
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();

      interactor->SetRenderWindow(renderWindow);

      vtkSmartPointer<vtkAxesActor> axes =
        vtkSmartPointer<vtkAxesActor>::New();
      axes->AxisLabelsOff();
      axes->SetTotalLength(5,5,5);

      leftRenderer->AddActor(axes);
      leftRenderer->AddActor(actor1a);
      leftRenderer->AddActor(actor1b);

      rightRenderer->AddActor(axes);
      rightRenderer->AddActor(actor2a);
      rightRenderer->AddActor(actor2b);

      leftRenderer->ResetCamera();
      rightRenderer->ResetCamera();

      renderWindow->Render();

      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(TransformOrderDemo)

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

    add_executable(TransformOrderDemo MACOSX_BUNDLE TransformOrderDemo.cxx)

    target_link_libraries(TransformOrderDemo ${VTK_LIBRARIES})

### Download and Build TransformOrderDemo

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

    cd TransformOrderDemo/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:

    ./TransformOrderDemo

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.