VTK: The Visualization Toolkit

1. VTK: The Visualization Toolkit Qaiser Chaudry Georgia Institute of Technology June 28, 2006

2. Visualization Box ?

3. What is VTK? • An open source, freely available software system for 3D graphics, image processing, and visualization. • Support for hundreds of algorithms in visualization and image processing • Object-oriented design with different interpreted language wrapers.

4. At a Glance • The core of VTK is written entirely in C++ • Contains 600 existing classes with 325K lines of code • VTK will compile and run on Windows 98/NT, SGI, Linux, Sun, HP, etc. • Supports OpenGL • Different interfaces for fast prototyping: Tcl , Java, and Python • Has users all over the world – The beauty of Open Source!

5. Interpreted Wrapper (Tcl, Java, Python) • Tcl/Tk shell • Java interpreter • Python interpreter • Tcl/Tk source • Java JDK • Python source C++ core All class source code (could take hours to compile) Libraries and includes (dll and .h files) Or (.a and .h files) Binary Installation: if you will use the classes to build your applicatoin Source code Installation: If you want to extend vtk System Architecture

6. VTK classes

7. The Graphics Model The purpose is to render the geometry (volume) on the screen vtkCamera vtkActor • vtkProperty • vtkMapper • vtkTransform vtkLight vtkRenderWindow vtkRenderer vtkRenderWindowInteractor

8. To see is to believe … 1 vtkRenderWindow vtkCamera 2 vtkRenderer vtkLight vtkActor ( property, geometry(mapper), transformation, etc)

9. camera Light screen Actor The Graphics Model The purpose is to render the geometry (volume) on the screen

10. Example Program Main() { create a window; create a renderer; give the renderer to the window; create procedural geometry; create a mapper; give the geometry to the mapper; create an actor; give the mapper to the actor; give the actor to the renderer; window->render(); } Window Renderer Actor Mapper Geometry

11. Example -1 • A polygonal model of a cone • Render to screen. • Rotate the cone 360 degrees • source -> mapper -> actor -> renderer -> renderwindow

12. Example -1 // First include the required header files for the VTK classes we are using. #include "vtkConeSource.h" #include "vtkPolyDataMapper.h" #include "vtkRenderWindow.h" #include "vtkCamera.h" #include "vtkActor.h" #include "vtkRenderer.h“ int main( int argc, char *argv[] ) { // Create an instance of vtkConeSource. vtkConeSource *cone = vtkConeSource::New(); cone->SetHeight( 3.0 ); cone->SetRadius( 1.0 ); cone->SetResolution( 10 );

13. Example -1 // We create an instance of vtkPolyDataMapper vtkPolyDataMapper *coneMapper = vtkPolyDataMapper::New(); coneMapper->SetInput( cone->GetOutput() ); // Create an actor. vtkActor *coneActor = vtkActor::New(); coneActor->SetMapper( coneMapper ); // Create the renderer. vtkRenderer *ren1= vtkRenderer::New(); ren1->AddActor( coneActor ); ren1->SetBackground( 0.1, 0.2, 0.4 ); // Finally we create the render window. vtkRenderWindow *renWin = vtkRenderWindow::New(); renWin->AddRenderer( ren1 ); renWin->SetSize( 300, 300 );

14. Example -1 // Now we loop over 360 degrees and render the cone each time. int i; for (i = 0; i < 360; ++i) { // Render the image. renWin->Render(); // Rotate the active camera by one degree. ren1->GetActiveCamera()->Azimuth( 1 ); // Introduce delay to slow down motion. Sleep(10); } // Free up any objects we created. cone->Delete(); coneMapper->Delete(); coneActor->Delete(); ren1->Delete(); renWin->Delete(); return 0; }

15. Creating Multiple Renderers vtkRenderer *ren1= vtkRenderer::New(); ren1->AddActor( coneActor ); ren1->SetBackground( 0.1, 0.2, 0.4 ); ren1->SetViewport(0.0, 0.0, 0.5, 1.0); vtkRenderer *ren2= vtkRenderer::New(); ren2->AddActor( coneActor ); ren2->SetBackground( 0.2, 0.3, 0.5 ); ren2->SetViewport(0.5, 0.0, 1.0, 1.0); vtkRenderWindow *renWin = vtkRenderWindow::New(); renWin->AddRenderer( ren1 ); renWin->AddRenderer( ren2 ); renWin->SetSize( 600, 300 );

16. Creating Multiple Renderers // Make one view 90 degrees from the other. ren1->GetActiveCamera()->Azimuth(90); // Now we loop over 360 degrees and render the cone each time. int i; for (i = 0; i < 360; ++i) { // render the image renWin->Render(); // rotate the active camera by one degree ren1->GetActiveCamera()->Azimuth( 1 ); ren2->GetActiveCamera()->Azimuth( 1 ); Sleep(10); }

17. Properties and Transformation // Create an actor to represent the first cone. The actor's properties are modified to give it different surface properties. By default, an actor is created with a property so the GetProperty() method can be used. vtkActor *coneActor = vtkActor::New(); coneActor->SetMapper( coneMapper ); coneActor->GetProperty()->SetColor(0.2, 0.63, 0.79); coneActor->GetProperty()->SetDiffuse(0.7); coneActor->GetProperty()->SetSpecular(0.4); coneActor->GetProperty()->SetSpecularPower(20);

18. Properties and Transformation // Create a property and directly manipulate it. Assign it to the second actor. vtkProperty *property = vtkProperty::New(); property->SetColor(1.0, 0.3882, 0.2784); property->SetDiffuse(0.7); property->SetSpecular(0.4); property->SetSpecularPower(20); vtkActor *coneActor2 = vtkActor::New(); coneActor2->SetMapper(coneMapper); coneActor2->GetProperty()->SetColor(0.2, 0.63, 0.79); coneActor2->SetProperty(property); coneActor2->SetPosition(0, 3, 0);

19. Properties and Transformation // Create the renderer and assign actors to it. vtkRenderer *ren1= vtkRenderer::New(); ren1->AddActor( coneActor ); ren1->AddActor( coneActor2 ); ren1->SetBackground( 0.1, 0.2, 0.4 );

20. User interaction • vtkRenderWindowInteractor – allow the user to interact with the graphics objects • w: wireframe mode • s: surface mode • r: reset the transformation • e: exit • Left Button: rotate • Right Button: zoom

21. User interaction // The vtkRenderWindowInteractor class watches for events (e.g., keypress, mouse) in the vtkRenderWindow. vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New(); iren->SetRenderWindow(renWin); // Here we specify a particular interactor style. vtkInteractorStyleTrackballCamera *style = vtkInteractorStyleTrackballCamera::New(); iren->SetInteractorStyle(style); // Leave an event loop running. Exit when the user presses the "e" key. iren->Initialize(); iren->Start();

22. TCL Vs C++ #include "vtkConeSource.h" #include "vtkPolyDataMapper.h" #include "vtkRenderWindow.h" #include "vtkCamera.h" #include "vtkActor.h" #include "vtkRenderer.h" int main( int argc, char *argv[] ){ vtkConeSource *cone = vtkConeSource::New(); cone->SetHeight( 3.0 ); cone->SetRadius( 1.0 ); cone->SetResolution( 10 ); vtkPolyDataMapper *coneMapper = vtkPolyDataMapper::New(); coneMapper->SetInput( cone->GetOutput() ); vtkActor *coneActor = vtkActor::New(); coneActor->SetMapper( coneMapper ); vtkRenderer *ren1= vtkRenderer::New(); ren1->AddActor( coneActor ); ren1->SetBackground( 0.1, 0.2, 0.4 ); vtkRenderWindow *renWin = vtkRenderWindow::New(); renWin->AddRenderer( ren1 ); renWin->SetSize( 300, 300 ); int i; for (i = 0; i < 360; ++i) { Sleep(10); renWin->Render(); ren1->GetActiveCamera()->Azimuth( 1 ); } cone->Delete(); coneMapper->Delete(); coneActor->Delete(); ren1->Delete(); renWin->Delete(); return 0;} package require vtk vtkConeSource cone cone SetHeight 3.0 cone SetRadius 1.0 cone SetResolution 10 vtkPolyDataMapper coneMapper coneMapper SetInput [cone GetOutput] vtkActor coneActor coneActor SetMapper coneMapper vtkRenderer ren1 ren1 AddActor coneActor ren1 SetBackground 0.1 0.2 0.4 vtkRenderWindow renWin renWin AddRenderer ren1 renWin SetSize 300 300 for {set i 0} {$i < 360} {incr i} { after 10 renWin Render [ren1 GetActiveCamera] Azimuth 1 } vtkCommand DeleteAllObjects exit

23. Demos • Diffuse Lighting • Modeling • Volume Rendering • 3D Model Motor • Medical imaging

24. What is ITK? National Library of Medicine Insight Segmentation and Registration Toolkit (ITK) • Image Processing • Segmentation • Registration • No Graphical User Interface (GUI) • No Visualization

25. References • www.cse.ohio-state.edu/~hwshen/788/sp01/ • http://www.kitware.com/ • http://www.vtk.org/ • The VTK Users's Guide • The Visualization Toolkit An Object-Oriented Approach To 3D Graphics 3rd Edition • http://www.itk.org/