vtk visualizationtoolkit introduction

VTK Visualization Toolkit

Introduction

Carlos A. [email protected]

Department of Physics ISEP School of EngineeringPolytechnic Institute of Porto

Porto, PORTUGAL

Outline

VTK Introduction Resources

Installation

VTK Architecture Low level object model

VTK file format

Rendering Engine

Visualization pipeline

Minimal Example

VTK Programming

VTK Interactors

Computer Hands-On Build VTK with Cmake

Test VTK Helloworld

Cone1.cxx

Cone2.cxx

Cone3.cxx

SingleScreenShot

Learn by Examples 3D Graphics

Visualization Techniques

Imaging

Carlos Vinhais VTK - Visualization Toolkit 2

VTK - Visualization Toolkit

Introduction Free open source software for 3D computer graphics, image processing

and visualization

Consists of a C++ class library VTK classes implemented with .h and .cxx file

Several interpreted interface layers, including Python, Tcl/Tk, and Java

Supports a wide variety of visualization algorithms including scalar, vector, tensor, texture, and volumetric

Advanced modeling techniques implicit modeling, polygon reduction, mesh smoothing, cutting, contouring

and Delaunay triangulation

Design and implementation influenced by object-oriented principles



Resources Source distribution (source and binaries)

www.vtk.org, Kitware, Inc.

Distribution comes with many examples

DocumentationOnline help, HTML based

http://www.vtk.org/doc/release/5.8/html/

Companion Text Books The Visualization Toolkit

The VTK Users Guide

www.kitware.com

Mailing lists, Links, FAQ, Search



Installation

1. Choose OS and install compiler/IDE Tested on Windows 7

MS Visual C++ 2010 Express Edition

2. CMake installation requiredwww.cmake.org (cmake-2.8.7-win32-x86.exe)

3. Get VTK source code vtk-5.8.0.zip

4. Run Cmake to configure and generate the VTK project

5. Compile VTK libraries

6. Test VTK with the exrecises


Cmake used to generate projects, makefiles or

workspaces For different compilers and OS. Cmake

is Cross platform.

VTK Architecture

Object Model Dataset types found in VTK

Image data

Rectilinear grid

Structured grid

Unstructured points

Polygonal Data

Unstructured grid

Data objects have geometric and topological structure (points and cells)

Cells are topological arrangements of points


VTK Architecture

Object Model

Reference Counting

vtkObjectBase * obj = vtkExampleClass::New();otheObject -> SetExample(obj);Obj -> Delete();

Smart Pointers

Class template vtkSmartPointer

vtkSmartPointer obj = vtkSmartPointer ::New();

otheObject -> SetExample(obj);


VTK Architecture

Object Model

Associated with the

points and cells of a

dataset

scalar

vector

normal

texture coordinate

tensor

field data


VTK File Format

STRUCTURED POINTS

(e.g. volume leon22.vtk)

# vtk DataFile Version 3.0VTK File Generated by Insight Segmentation and Registration Toolkit (ITK)BINARYDATASET STRUCTURED_POINTSDIMENSIONS 512 512 64SPACING 0.703125 0.703125 5ORIGIN -173.3 -180 -269.75POINT_DATA 16777216SCALARS scalars short 1LOOKUP_TABLE default ......

POLYDATA - unstructured points

(e.g. teste_02_001.vtk)

# vtk DataFile Version 3.0vtk outputASCIIDATASET POLYDATAPOINTS 77268 float75.9892 41.9058 932.34975.7524 41.8747 932.064...

VERTICES 77268 1545361 0 1 1 ...


VTK Architecture

Rendering EngineA VTK scene consists of:

vtkRenderWindowInteractor window interaction

vtkRenderWindow contains the final image

vtkRenderer draws into the render window

vtkActor combines properties/geometry

vtkMapper represents geometry

vtkProp, vtkProp3D Superclasses

vtkProperty

vtkLights illuminate actors

vtkCamera renders the scene

vtkTransform position actors


VTK Architecture

Visualization Pipeline

Visualization pipeline transforms information into graphical data Uses a data flow approach

Two basic types of objects: vtkDataObject and vtkProcessObject

Pipeline topology based on filter I/O Filters operate on data objects to produce new data objects

thisFilter -> setInput( thatFilter->getOutput() );

Pipeline execution

Visualization pipelines use lazy evaluation

Only executes when data is required for computation


VTK Architecture


data objects combined with process object to create the

visualization pipeline

Pipeline execution


VTK Architecture


Types of algorithms

multiplicity of input and output


Minimal Example

Cone1

Basic setup for VTK programs Programming implementation of basic

VTK exercises:

Data source Procedural data, cone, sphere, cylinder,

etc.

Or data read from a file

vtkMapper and vtkLookupTable Transform and render geometry

Interface between the viz pipeline and the graphics model

vtkScalarToColorsmaps data values to color

vtkActors Combine object properties, geometries

and orientation in virtual coordinates

vtkRenderer Coordinates lights, cameras and actors

to create an image

vtkRenderWindow Manages the rendering process on the

render window(s) on display device

vtkRenderWindowInteractor Connection between the operating

system and the VTK rendering engine


Minimal Example

Cone1


// C++// The basic setup of:// source->mapper->actor->renderer->renderwindow// is typical of most VTK programs.

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 *renderer = vtkRenderer::New();renderer -> AddActor( coneActor );renderer -> SetBackground(0.1, 0.2, 0.4);

vtkRenderWindow *renderWindow = vtkRenderWindow::New();

renderWindow -> AddRenderer( renderer );renderWindow -> SetSize( 300, 300 );

vtkRenderWindowInteractor *renderWindowInteractor = vtkRenderWindowInteractor::New();

renderWindowInteractor -> SetRenderWindow( renderWindow );

renderWindow -> Render();renderWindowInteractor -> Start();

VTK Programming

Conversions between languages relatively straightforward

Class names and method names remain the same

Implementation details change (syntax)

GUI details change

Example

C++ ren1->GetActiveCamera()->Azimuth( 1 ); Python ren1.GetActiveCamera().Azimuth( 1 ) Tcl [ren1 GetActiveCamera] Azimuth 1 Java ren1.GetActiveCamera().Azimuth( 1 );


VTK Programming


# Python# The basic setup of: # source->mapper->actor->renderer->renderwindow# is typical of most VTK programs.

cone = vtk.vtkConeSource()cone.SetHeight( 3.0 )cone.SetRadius( 1.0 )cone.SetResolution( 10 )

coneMapper = vtk.vtkPolyDataMapper()coneMapper.SetInput( cone.GetOutput() )

coneActor= vtk.vtkActor()coneActor.SetMapper( coneMapper)

ren1= vtk.vtkRenderer()ren1.AddActor( coneActor)ren1.SetBackground( 0.1, 0.2, 0.4 )

renWin= vtk.vtkRenderWindow()renWin.AddRenderer( ren1 )renWin.SetSize( 300, 300 )

...

// C++// The basic setup of:// source->mapper->actor->renderer->renderwindow// is typical of most VTK programs.

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 *renderer = vtkRenderer::New();renderer -> AddActor( coneActor );renderer -> SetBackground(0.1, 0.2, 0.4);

vtkRenderWindow *renderWindow = vtkRenderWindow::New();

renderWindow -> AddRenderer( renderer );renderWindow -> SetSize( 300, 300 );

vtkRenderWindowInteractor *renderWindowInteractor = vtkRenderWindowInteractor::New();

renderWindowInteractor -> SetRenderWindow( renderWindow );


VTK Interactors

vtkRenderWindowInteractor

Keypress: j|t Toggle between joystick or trackball mode

In joystick style the motion occurs continuously as long as the mouse button is pressed

In trackball style the motion occurs when the mouse button is pressed and the mouse cursor moves

Keypress: c|a Toggle between camera and actor modes

In camera mode, the mouse events affect the camera position and focal point

In actor mode, the mouse events affect the object under the mouse pointer

Keypress: e|q Exit/quit application

Keypress: 3 Toggle in and out of stereo model

Default is red-blue stereo pairs

Left Mouse Button Rotate camera or actor

Camera rotated around its focal point

Actor rotated around its origin

Middle Mouse Button Pan camera or translate actor

In joystick mode direction of pan/translation is from center of the viewporttoward the mouse position

In trackball mode, direction of motion in the direction of the mouse movement MMB

Right Mouse Button Zoom camera or scale actor

Zoom in/increase scale in top half of the viewport

Zoom out/decrease scale in lower half of the viewport

In joystick mode amount is controlled by distance of the pointer from the horizontal center line


VTK Interactors

Keypress u Invokes user-defined mode

brings up an command interactor window

Rerender using irenRender

Keypress f Fly-to the point under the cursor

Sets the focal point allowing rotations about that point

Keypress p Pick operation

Render window has an internal instance of vtkPropPickerfor picking

Keypress r Reset the camera along the viewing direction

Centers the actors

All actors visible

Keypress s All actors represented as surfaces

Keypress w All actors represented in wire frame


solid

wired

stereo

Computer Hands-On

Build and Test VTK

Build VTK

Follow the notes!

Install_Notes_VTK5_VC2010_Win64.pdf

Test VTK

Get the source code!

Helloworld.zip (CMakeLists.txt + Helloworld.cxx)

Requires ITK installed!


Computer Hands-On

VTK Exercises

Cone1

Cone2

Cone3

SingleScreenShot


Full screen, stereo

1 window, 3 viewports

Computer Hands-On

SingleScreenShot

#include #include

#include #include

...

renderWindow -> SetSize( 512, 512 );// set window size

renderWindow -> StereoCapableWindowOn();renderWindow -> StereoRenderOn();renderWindow -> SetStereoTypeToAnaglyph();//renderWindow -> SetStereoTypeToCrystalEyes();//renderWindow -> SetStereoTypeToLeft();renderWindow -> StereoUpdate();

renderWindow->FullScreenOn(); //WILL RENDER IN STEREO



Full screen, stereo

Computer Hands-On

SingleScreenShot (cont.)...


vtkSmartPointer< vtkWindowToImageFilter > windowToImageFilter = vtkSmartPointer< vtkWindowToImageFilter >::New();

windowToImageFilter -> SetInput( renderWindow );windowToImageFilter -> Update();

vtkSmartPointer< vtkPNGWriter > writer = vtkSmartPointer< vtkPNGWriter >::New();

writer -> SetFileName( "SingleScreenshot.png" );writer -> SetInput( windowToImageFilter->GetOutput() );writer -> Write();

...


3D Graphics

Surface rendering

Volume rendering

Ray casting

Texture mapping (2D)

Lights and cameras

Textures

Save render window to .png, .jpg, ...

(useful for movie creation)

...



Scalar algorithms

Contouring

Color mapping

Vector algorithms

Streamlines

streamtubes

Tensor algorithms

Tensor ellipsoids


Imaging

vtkImageToImageFilter

Diffusion

High-pass / Low-pass (Fourier)

Convolution

Gradient (magnitude)

Distance map

Morphology

Skeletons



Contouring Contouring

Also Iso-surfaces

Filter vtkContourFilter performs the function

Using SetValue() method contours SetValue 0.0 0.5

Using GenerateValues() method Contours generateValues 8 0.0 1.2

Specify range and number of contours

Many methods perform contouring vtkMarchingCubes

vtkMarchingSquares



Color Mapping Coloring objects by scalar values

Scalar values mapped through lookup table

Color applied during rendering

Modifies appearance of points or cells

Use any data array Method ColorByArrayComponent()

If not specified, a default lookup table is created by the mapper


3D Widgets

Watch for events invoked by vtkRenderWindowInteractor

Subclasses of vtkInteractorObserver

List of most important widgets vtkScalarBarWidget

vtkPointWidget

vtkLineWidget

vtkPlaneWidget

vtkImplicitPlane

vtkBoxWidget

vtkImagePlaneWidget

vtkSphereWidget

vtkSplineWidget



Cutting Create cross-section of dataset

Any implicit function Planes create planar cuts

Cutting surface interpolates the data

Result is always type vtkPolyData

vtkCutter needs an implicit function to cut

May use more cut values SetValue() method

GenerateValues() method

Values specify the value of the implicit function

Cutting values Zero precisely on the implicit function

Less than zero, below

Greater than zero, above

Only strictly true for vtkPlane



Merging and Probing Merge data

Pipelines could have loops

Multiple streams of the pipeline

vtkMergeFilter merges data from several datasets to a new dataset

Probing vtkAppendFilter builds new

dataset by appending datasets Specialized filter

vtkAppendPolyData

Only data attributes common to all data input are appended



Glyphing Represent data using symbols, or

glyphs

Simple glyphs Cone oriented to a vector

Complex Symbolic representation of the

human face

Expression controlled by the data values

vtkGlyph3D class Scaled, colored

Orientated along a direction

Glyphs copied to each point of the dataset

Glyphs defined by second input to the filter

Glyphs of type vtkPolyData



Glyphing

The glyph uses the point attribute normals for orientation

Use vector data using the SetVectorMethodToUseVector()

Scale glyphs by scalar data using SetScaleModeToScaleByScalar()

Turn data scaling off using SetScaleModeToDataScalingOff()

Many other options



Streamlines

Streamlines

Path of a massless particle in a vector field

Requires starting point(s)

Integration direction

Along the flow

Opposite the flow

Both



Streamsurfaces

Series of ordered points, used to generate streamlines

vtkRuledSurfaceFilter used to create a surface

Points must be ordered carefully

Assumes points lie next to one another

Within a specified distance of neighbors (DistanceFactorvariable)


VTK Example

The Virtual Frog


http://www-itg.lbl.gov/Frog

End of VTK Lecture.

Thank you!

Carlos A. [email protected]

Department of Physics ISEP School of EngineeringPolytechnic Institute of Porto

Porto, PORTUGAL

vtk visualizationtoolkit introduction

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