VTK: The Visualization Toolkit

Qaiser Chaudry

Georgia Institute of Technology

June 28, 2006

Visualization

Box ?

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.

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!

System ArchitectureInterpreted Wrapper (Tcl, Java, Python)

C++ core

Binary Installation: if you will usethe classes to build your applicatoin

Source code Installation: If you want to extend vtk

•Tcl/Tk source•Java JDK•Python source

All class source code(could take hours to compile)

Libraries and includes(dll and .h files)Or(.a and .h files)

•Tcl/Tk shell•Java interpreter•Python interpreter

VTK classes

The Graphics Model

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

vtkCameravtkLight

vtkActor

•vtkProperty•vtkMapper•vtkTransformvtkRenderWindow

vtkRenderervtkRenderWindowInteractor

To see is to believe …1 vtkRenderWindow

2 vtkRenderervtkCamera

vtkLight

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

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

cameraLightActor

screen

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

Example -1

• A polygonal model of a cone

• Render to screen.

• Rotate the cone 360 degrees

• source -> mapper -> actor -> renderer -> renderwindow

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 );

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 );

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;}

Creating Multiple RenderersvtkRenderer *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 );

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); }

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);

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);

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 );

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

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();

TCL Vs C++

package require vtk

vtkConeSource conecone SetHeight 3.0cone SetRadius 1.0cone SetResolution 10

vtkPolyDataMapper coneMapperconeMapper SetInput [cone GetOutput]

vtkActor coneActorconeActor SetMapper coneMapper

vtkRenderer ren1 ren1 AddActor coneActorren1 SetBackground 0.1 0.2 0.4

vtkRenderWindow renWinrenWin AddRenderer ren1renWin SetSize 300 300

for {set i 0} {$i < 360} {incr i} { after 10 renWin Render [ren1 GetActiveCamera] Azimuth 1}

vtkCommand DeleteAllObjects

exit

#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;}

Demos

• Diffuse Lighting

• Modeling

• Volume Rendering

• 3D Model Motor

• Medical imaging

What is ITK?

• Image Processing

• Segmentation

• Registration

• No Graphical User Interface (GUI)

• No Visualization

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

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/