Medical Image Processing and Analysis Lecture -12

1 Dr. Qaiser Chaudry

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.

Dr. Qaiser Chaudry

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, SGI, Linux, Sun, HP, etc. • Support OpenGL • Different interfaces for fast prototyping: Tcl , Java, and Python • Have users all over the world – The beauty of Open Source!

Dr. Qaiser Chaudry

System Architecture Interpreted Wrapper (Tcl, Java, Python) •Tcl/Tk shell •Java interpreter •Python interpreter

•Tcl/Tk source •Java JDK •Python source

C++ core Libraries and includes All class source code (could take hours to (dll and .h files) compile) Or (.a and .h files)

Binary Installation: if you will use The classes to build your applicatoin

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Source code Installation: If you want to extend vtk

VTK classes

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The Graphics Model The purpose is to render the geometry (volume) on the screen vtkCamera

vtkRenderWindow vtkRenderWindowInteractor

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vtkActor

vtkLight

•vtkProperty •vtkMapper •vtkTransform vtkRenderer

To see is to believe … 1 vtkRenderWindow

2 vtkRenderer

vtkCamera vtkLight vtkActor ( property, geometry(mapper), transformation, etc)

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The Graphics Model The purpose is to render the geometry (volume) on the screen camera

screen

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Actor

Light

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;

}

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give the actor to the renderer; window->render();

Window Renderer Actor Mapper Geometry

Example -1 • • • •

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

Example -1 # # This example creates a polygonal model of a cone, and then rendered it to # the screen. It willrotate the cone 360 degrees and then exit. The basic # setup of source -> mapper -> actor -> renderer -> renderwindow is # typical of most VTK programs. # # # First we include the VTK Tcl packages which will make available # all of the vtk commands to Tcl # package require vtk # # Next we create an instance of vtkConeSource and set some of its # properties # vtkConeSource cone cone SetHeight 3.0 cone SetRadius 1.0 cone SetResolution 10

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Example -1 # # We create an instance of vtkPolyDataMapper to map the polygonal data # into graphics primitives. We connect the output of the cone souece # to the input of this mapper # vtkPolyDataMapper coneMapper coneMapper SetInput [cone GetOutput] # # create an actor to represent the cone. The actor coordinates rendering of # the graphics primitives for a mapper. We set this actor's mapper to be # coneMapper which we created above. # vtkActor coneActor coneActor SetMapper coneMapper # # Create the Renderer and assign actors to it. A renderer is like a # viewport. It is part or all of a window on the screen and it is responsible # for drawing the actors it has. We also set the background color here # vtkRenderer ren1 ren1 AddActor coneActor ren1 SetBackground 0.5 0.2 0.4

Dr. Qaiser Chaudry

Example -1 # # Finally we create the render window which will show up on the screen # We put our renderer into the render window using AddRenderer. We also # set the size to be 300 pixels by 300 # vtkRenderWindow renWin renWin AddRenderer ren1 renWin SetSize 300 300 # # now we loop over 360 degreeees and render the cone each time # for {set i 0} {$i < 360} {incr i} { after 20 # render the image renWin Render # rotate the active camera by one degree [ren1 GetActiveCamera] Azimuth 1 } # # Free up any objects we created # vtkCommand DeleteAllObjects

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Creating Multiple Renderers •

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

• • • • •

#add viewport vtkRenderer ren1 ren1 AddActor coneActor ren1 SetBackground 0.5 0.2 0.4 ren1 SetViewport 0.0 0.0 0.5 1.0

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Creating Multiple Renderers • • • • •

# added 2nd renderer vtkRenderer ren2 ren2 AddActor coneActor ren2 SetBackground 0.0 0.5 0.4 ren2 SetViewport 0.5 0.0 1.0 1.0

• • • • •

# add both renderers to window and change size vtkRenderWindow renWin renWin AddRenderer ren1 renWin AddRenderer ren2 renWin SetSize 600 300

• • • • • •

for {set i 0} {$i < 360} {incr i} { after 20 renWin Render [ren1 GetActiveCamera] Azimuth 1 [ren2 GetActiveCamera] Azimuth 1 }

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User interaction • vtkRenderWindowInteractor – allow the user to interact with the graphics objects

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•

w: wireframe mode

•

Left Button: rotate

•

s: surface mode

•

Right Button: zoom

•

r: reset the transformation

•

e: exit

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();

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User interaction vtkRenderWindow renWin renWin AddRenderer ren1 renWin SetSize 300 300 renWin Render # create rendrer window interactor vtkRenderWindowInteractor iren iren SetRenderWindow renWin # Add observer and initialize interactor iren AddObserver UserEvent {wm deiconify .vtkInteract} iren Initialize # prevent the tk window from showing up then start the event loop wm withdraw .

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Demos • Bottle • Spring • 3D Model Motor • Medical imaging • Stomach model

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What is ITK?

National Library of Medicine Insight Segmentation and Registration Toolkit (ITK)

• Image Processing • Segmentation • Registration • No Graphical User Interface (GUI) • No Visualization

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References • • • • • •

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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/