scientific visualization using vtk

Scientific Visualization Using VTKScientific Visualization Using VTK

Robert [email protected]

Scientific Visualization Using VTK – Spring 2012

OutlineOutline

• Introduction• VTK overview• VTK data geometry/topology• Case study• Interactive session


IntroductionIntroduction


*Adapted from The ParaView Tutorial, Moreland

• Visualization: converting raw data to a form that is viewable and understandable to humans.

• Scientific visualization: specifically concerned with data that has a well-defined representation in 2D or 3D space (e.g., from simulation mesh or scanner).

VTKVTKVisualization Toolkit

– Inception at GE in 1993; since 1998 spun off to “Kitware”, supported by Sandia Labs.

– Open source– Set of object-oriented class libraries for visualization and data analysis– Several language interfaces

• C++• Tcl• Java• Python

– Portable (MS Windows, Linux, OSX)– Active developer community– Good documentation available, free and otherwise– Professional support services available from Kitware


Generic visualization pipelineGeneric visualization pipeline


Source(s) Filters(s) Output - - - - - - - - - - - - - - - - - - - - -

data/geometry/topology graphics

VTK terminology/modelVTK terminology/model


Source Filter Renderer

- - - - - - - - - - - - - - - - - - - - -


Mapper

VTK terminology/modelVTK terminology/model


Source/ Reader

Filter Renderer

- - - - - - - - - - - - - - - - - - - - -


Mapper

“Scene"

Lights, Camera

DataObject ProcessObject

Actor

RenderWindow

vtkStructuredGridReader *reader = vtkStructuredGridReader::New(); reader->SetFileName("density.vtk"); reader->Update();

vtkContourFilter *iso = vtkContourFilter::New(); iso->SetInputConnection(reader->GetOutputPort()); iso->SetValue(0,0.26);

vtkPolyDataMapper *isoMapper = vtkPolyDataMapper::New(); isoMapper->SetInputConnection(iso->GetOutputPort());

vtkActor *isoActor = vtkActor::New(); isoActor->SetMapper(isoMapper);

vtkRenderer *ren1 = vtkRenderer::New(); ren1->AddActor(isoActor);

vtkRenderWindow *renWin = vtkRenderWindow::New(); renWin->SetSize(500,500); renWin->AddRenderer(ren1);

Pipeline -> Sample CodePipeline -> Sample Code


Reader

Filter

Mapper

Actor

Renderer

RenderWindow

C++ v. TclC++ v. Tcl

• C++

• Tcl


vtkStructuredGridReader readerreader SetFileName "density.vtk"reader Update

vtkContourFilter isoiso SetInputConnection [reader GetOutputPort]iso SetValue 0 .26

vtkStructuredGridReader *reader = vtkStructuredGridReader::New();reader->SetFileName("density.vtk");reader->Update();

vtkContourFilter *iso = vtkCountourFilter::New();iso->SetInputConnection(reader->GetOutputPort());iso->SetValue(0, .26);

Coding tip of the day!Coding tip of the day!

• Google “VTK class list”, or• Go to:

http://www.vtk.org/doc/nightly/html/annotated.html


http://www.vtk.org/doc/nightly/html/annotated.html

VTK – Geometry v. TopologyVTK – Geometry v. Topology Geometry of a dataset ~= points


0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

Topology ~= connections among points, which define cells

So, what’s the topology here?

VTK – Geometry v. TopologyVTK – Geometry v. Topology


0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0



0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

or

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0



or

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

or

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0



or

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

or

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

or

0,1 1,1 2,1 3,1

0,0 1,0 2,0 3,0

Geometry/Topology StructureGeometry/Topology Structure Geometry/topology may be regular or irregular

– Regular (structured)• need to store only beginning position, spacing, number of points• smaller memory footprint per cell (topology can be generated on the fly)• examples: image data, rectilinear grid, structured grid

– Irregular (unstructured)• information can be represented more densely where it changes quickly • higher memory footprint (topology must be explicitly written) but more freedom• examples: polygonal data, unstructured grid


Characteristics of DataCharacteristics of Data Data is organized into datasets for visualization

– Datasets consist of two pieces• organizing structure

– points (geometry)– cells (topology)

• data attributes associated with the structure– File format derived from organizing structure


Data is discrete– Interpolation functions generate data values in between known points

Examples of Dataset TypesExamples of Dataset Types Structured Points (Image Data)

– regular in both topology and geometry– examples: lines, pixels, voxels– applications: imaging CT, MRI

Rectilinear Grid– regular topology but geometry only partially

regular– examples: pixels, voxels

Structured Grid (Curvilinear)– regular topology and irregular geometry– applications: fluid flow, heat transfer


Examples of Dataset Types (cont)Examples of Dataset Types (cont) Polygonal Data

– irregular in both topology and geometry– examples: vertices, polyvertices, lines,

polylines, polygons, triangle strips

Unstructured Grid – irregular in both topology and geometry– examples: any combination of cells– applications: finite element analysis,

structural design, vibration


Examples of Cell TypesExamples of Cell Types


Data AttributesData Attributes Data attributes associated with the organizing structure

– Scalars • single valued• examples: temperature, pressure, density, elevation

– Vectors• magnitude and direction• examples: velocity, momentum

– Normals • direction vectors (magnitude of 1) used for shading

– Texture Coordinates• used to map a point in Cartesian space into 1, 2, or 3D texture space• used for texture mapping

– Tensors • 3x3 only• examples: stress, strain


File Format – Structured PointsFile Format – Structured Points


Editor structured-points.vtk:# vtk DataFile Version 3.0

first dataset

ASCII

DATASET STRUCTURED_POINTS

DIMENSIONS 3 4 5

ORIGIN 0 0 0

SPACING 1 1 2

POINT_DATA 60

SCALARS temp-point float

LOOKUP_TABLE default

0 0 0 1 1 1 1 1 1 0 0 0

0 0 0 1 1 1 1 1 1 0 0 0

0 0 0 1 1 1 1 1 1 0 0 0

0 0 0 1 1 1 1 1 1 0 0 0

0 0 0 1 1 1 1 1 1 0 0 0

File Format – Structured PointsFile Format – Structured Points


Editor structured-points2.vtk:# vtk DataFile Version 3.0

first dataset

ASCII

DATASET STRUCTURED_POINTS

DIMENSIONS 3 4 5

ORIGIN 0 0 0

SPACING 1 1 2

CELL_DATA 24

SCALARS temp-cell float

LOOKUP_TABLE default

0 0 1 1 0 0

0 0 1 1 0 0

0 0 1 1 0 0

0 0 1 1 0 0

Structured Points – C++ codeStructured Points – C++ code


Editor structured-points.cxx:vtkStructuredPointsReader *reader = vtkStructuredPointsReader::New();

reader->SetFileName("structured-points.vtk");

reader->Update();

vtkLookupTable *lut = vtkLookupTable::New();

lut->SetNumberOfColors(2);

lut->SetTableValue(0, 0.0, 0.0, 1.0, 1);

lut->SetTableValue(1, 1.0, 0.0, 0.0, 1);

vtkDataSetMapper *mapper = vtkDataSetMapper::New();

mapper->SetInputConnection(reader->GetOutputPort());

mapper->SetLookupTable(lut);

vtkActor *actor = vtkActor::New();

actor->SetMapper(mapper);

actor->GetProperty()->EdgeVisibilityOn();

actor->GetProperty()->SetLineWidth(2);

Structured Points – C++ code (cont.)Structured Points – C++ code (cont.)


Editor structured-points.cxx:vtkRenderer *ren1 = vtkRenderer::New();

ren1->AddActor(actor);

ren1->SetBackground(0.5,0.5,0.5);

vtkRenderWindow *renWin = vtkRenderWindow::New();

renWin->AddRenderer(ren1);

renWin->SetSize(500,500);

vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();

iren->SetRenderWindow(renWin);

iren->Initialize();

iren->Start();

Work flow – Case StudyWork flow – Case Study BU Space Physics simulation

Meteor trails in the ionosphere Data wrangling:

Consolidate datafiles (from parallel code), create single binary datafile

Add VTK header:


# vtk DataFile Version 3.0output of reassemble.cBINARYDATASET STRUCTURED_POINTSORIGIN 0.0 0.0 0.0SPACING 1.0 1.0 1.0DIMENSIONS 512 64 128POINT_DATA 4194304SCALARS plasma floatLOOKUP_TABLE default

Work flow – Case StudyWork flow – Case Study Use Tcl for fast development/testing:


vtkStructuredPointsReader reader reader SetFileName "opp.vtk" reader Update

vtkContourFilter iso iso SetInputConnection [reader GetOutputPort] iso SetValue 0 0.1

. . .

Work flow – Case StudyWork flow – Case Study Add gaussian filter :


vtkImageGaussianSmooth gaussian gaussian SetInputConnection [reader GetOutputPort] gaussian SetDimensionality 3 gaussian SetRadiusFactor 1 vtkContourFilter iso iso SetInputConnection [gaussian GetOutputPort] iso SetValue 0 0.1

. . .

Work flow – Case StudyWork flow – Case Study Add more isosurfaces :


vtkContourFilter iso iso SetInputConnection [gaussian GetOutputPort] iso SetValue 0 1.0 iso SetValue 1 0.5 iso SetValue 2 0.1

Work flow – Case StudyWork flow – Case Study Port to C++, add cutplane, transparency :


vtkPlane *plane = vtkPlane::New(); plane->SetOrigin(256,2,63.5); plane->SetNormal(0,1,0);

vtkCutter *planeCut = vtkCutter::New(); planeCut->SetInputConnection(reader>GetOutputPort()); planeCut->SetCutFunction(plane);

vtkActor *isoActor = vtkActor::New(); isoActor->SetMapper(isoMapper); isoActor->GetProperty()->SetOpacity(iv_opacity);

Work flow – Case StudyWork flow – Case Study Change color map, use script to loop over *.vtk, generate multiple

jpegs, read into Adobe Premiere, produce animation:


VTK – Getting Started - UIVTK – Getting Started - UI


Unix Shell: katana:% cone2

Keyboard shortcutsKeyboard shortcuts


j – joystick (continuous) modet – trackball mode

c –camera move modea –actor move mode

left mouse – rotate x,yctrl - left mouse – rotate zmiddle mouse –panright mouse –zoom

r –reset cameras/w –surface/wireframee (or q) –exit

Code – simple.cxxCode – simple.cxx


Editor: simple.cxx #include <stdio.h>

#include <stdlib.h>

#include "vtk-include.h"

int main(int argc, char *argv[]) {

vtkRenderer *ren1 = vtkRenderer::New();





renWin->Render();

sleep(2);

}

ExerciseExercise


Editor: simple2.cxx

Change background color to gray (or fuchsia, etc.)

Code – ExerciseCode – Exercise


Editor: simple2.cxx int main(int argc, char *argv[]) {






renWin->Render();

sleep(2);

}

Code – cone2.cxxCode – cone2.cxx


Editor cone2.cxx:vtkConeSource *cone = vtkConeSource::New();

cone->SetResolution(100);

vtkPolyDataMapper *coneMapper = vtkPolyDataMapper::New();

coneMapper->SetInputConnection(cone->GetOutputPort());

vtkActor *coneActor = vtkActor::New();

coneActor->SetMapper(coneMapper);

coneActor->GetProperty()->SetColor(1.0, 0.0, 0.0);



ren1->AddActor(coneActor);




vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();

iren->SetRenderWindow(renWin);

iren->Initialize();

iren->Start();

ExerciseExercise


Editor: cone3.cxx

Add coneActor2, and color it green. (Copy coneActor, and make appropriate changes. Remember to add the new actor to the render window [near the end of the “pipeline”].)

Optional: to rotate, scale and set the position away from the origin, use the following:

coneActor2->RotateZ(90); coneActor2->SetScale(0.5,0.5,0.5); coneActor2->SetPosition(-1.0,0.0,0.0);

Otherwise, use ‘a’ to use mouse to separate the green and red cones.

Code – ExerciseCode – Exercise


Editor: cone3.cxx. . .

vtkActor *coneActor2 = vtkActor::New();

coneActor2->SetMapper(coneMapper);

coneActor2->GetProperty()->SetColor(0.0, 1.0, 0.0);

coneActor2->RotateZ(90);

coneActor2->SetScale(0.5,0.5,0.5);

coneActor2->SetPosition(-1.0,0.0,0.0);

. . .

ren1->AddActor(coneActor);

ren1->AddActor(coneActor2);

. . .

VTK - ReadersVTK - Readers Image and Volume Readers

– vtkStructuredPointsReader - read VTK structured points data files– vtkSLCReader - read SLC structured points files– vtkTIFFReader - read files in TIFF format– vtkVolumeReader - read image (volume) files– vtkVolume16Reader - read 16-bit image (volume) files

Structured Grid Readers– vtkStructuredGridReader - read VTK structured grid data files– vtkPLOT3DReader - read structured grid PLOT3D files

Rectilinear Grid Readers– vtkRectilinearGridReader - read VTK rectilinear grid data files

Unstructured Grid Readers– vtkUnstructuredGridReader - read VTK unstructured grid data files


VTK - ReadersVTK - Readers Polygonal Data Readers

– vtkPolyDataReader - read VTK polygonal data files– vtkBYUReader - read MOVIE.BYU files– vtkMCubesReader - read binary marching cubes files– vtkOBJReader - read Wavefront (Maya) .obj files– vtkPLYReader - read Stanford University PLY polygonal data files– vtkSTLReader - read stereo-lithography files– vtkUGFacetReader - read EDS Unigraphic facet files

Image and Volume Readers (add’l)– vtkBMPReader - read PC bitmap files– vtkDEMReader - read digital elevation model files– vtkJPEGReader - read JPEG files– vtkImageReader - read various image files– vtkPNMReader - read PNM (ppm, pgm, pbm) files– vtkPNGRReader - read Portable Network Graphic files


File Format – Structured GridFile Format – Structured Grid


Editor density.vtk:# vtk DataFile Version 3.0

vtk sample data

ASCII

DATASET STRUCTURED_GRID

DIMENSIONS 57 33 25

POINTS 47025 float

2.667 -3.77476 23.8329 2.94346 -3.74825 23.6656 3.21986 -3.72175 23.4982

3.50007 -3.70204 23.3738 3.9116 -3.72708 23.5319 4.1656 -3.69529 23.3312

. . .

POINT_DATA 47025

SCALARS Density float

0.639897 0.239841 0.252319 0.255393 0.252118 0.246661 0.240134 0.234116 0.229199

0.225886 0.224268 0.224647 0.231496 0.246895 0.26417 0.27585 0.278987 0.274621

. . .

VECTORS Momentum float

0 0 0 13.753 -5.32483 -19.964 42.3106 -15.57 -43.0034

64.2447 -13.3958 -46.2281 73.7861 -4.83205 -36.3829 88.3374 6.23797 -22.8846

. . .

Clipping, Cutting, SubsamplingClipping, Cutting, SubsamplingSelection Algorithms - Clipping

• can reveal internal details of surface • VTK - vtkClipDataSet

- Cutting/Slicing• cutting through a dataset with a surface• VTK - vtkCutter

- Subsampling• reduces data size by selecting a subset of

the original data• VTK - vtkExtractGrid


Code – ClippingCode – Clipping


Editor: clipping.cxxvtkStructuredGridReader *reader = vtkStructuredGridReader::New();

reader->SetFileName("density.vtk");

reader->Update();

vtkPlane *plane = vtkPlane::New();

plane->SetOrigin(reader->GetOutput()->GetCenter());

plane->SetNormal(-0.287, 0, 0.9579);

vtkClipDataSet *clip = vtkClipDataSet::New();

clip->SetInputConnection(reader->GetOutputPort());

clip->SetClipFunction(plane);

clip->InsideOutOn();

vtkDataSetMapper *clipMapper = vtkDataSetMapper::New();

clipMapper->SetInputConnection(clip->GetOutputPort());

clipMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *clipActor = vtkActor::New();

clipActor->SetMapper(clipMapper);

Code – Cutplane/SlicingCode – Cutplane/Slicing


Editor: cutplane.cxxvtkStructuredGridReader *reader = vtkStructuredGridReader::New();


reader->Update();

vtkPlane *plane = vtkPlane::New();

plane->SetOrigin(reader->GetOutput()->GetCenter());

plane->SetNormal(-0.287, 0, 0.9579);

vtkCutter *planeCut = vtkCutter::New();

planeCut->SetInputConnection(reader->GetOutputPort());

planeCut->SetCutFunction(plane);

vtkPolyDataMapper *cutMapper = vtkPolyDataMapper::New();

cutMapper->SetInputConnection(planeCut->GetOutputPort());

cutMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *cutActor = vtkActor::New();

cutActor->SetMapper(cutMapper);*To see the cutplane with a colorbar guide, try ‘cutplane-with-colorbar’.

Code – ExtractGridCode – ExtractGrid


Editor: extract.cxxvtkStructuredGridReader *reader = vtkStructuredGridReader::New();


reader->Update();

vtkExtractGrid *extract = vtkExtractGrid::New();

extract->SetInputConnection(reader->GetOutputPort());

extract->SetVOI(-1000,1000,-1000,1000,7,10);

vtkDataSetMapper *extractMapper = vtkDataSetMapper::New();

extractMapper->SetInputConnection(extract->GetOutputPort());

extractMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *extractActor = vtkActor::New();

extractActor->SetMapper(extractMapper);

*Optional: enable EdgeVisibility inExtractActor.

Color MappingColor Mapping Scalar Algorithms

– Color Mapping • maps scalar data to colors• implemented by using scalar values as an index into a color

lookup table

– VTK • vtkLookupTable• vtkDataSetMapper


Code – Color MappingCode – Color Mapping


Editor: colormap.numcolors.cxx. . .

vtkStructuredGridReader *reader = vtkStructuredGridReader::New();

reader->SetFileName("subset.vtk");

reader->Update();


lut->SetNumberOfColors(16);

lut->SetHueRange(0.0, 0.667);

vtkDataSetMapper *mapper = vtkDataSetMapper::New();

mapper->SetInputConnection(reader->GetOutputPort());

mapper->SetLookupTable(lut);

mapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *actor = vtkActor::New();

actor->SetMapper(mapper);

ExerciseExercise


* Change the number of colors in colormap

* Reverse the Hue Range

* Change the Scalar Range [or see what happens if you don’t set it]mapper SetScalarRange 0.0 0.7

ContouringContouring Scalar Algorithms (cont)

– Contouring• construct a boundary between distinct regions, two steps:

– explore space to find points near contour– connect points into contour (2D) or surface (3D)

• 2D contour map (isoline):– applications: elevation contours from topography, pressure contours

(weather maps) from meteorology3D isosurface:• 3D isosurface:

– applications: tissue surfaces from tomography, constant pressure or temperature in fluid flow, implicit surfaces from math and CAD

– VTK• vtkContourFilter


Code – Contour (isoline)Code – Contour (isoline)


Editor: contour.single.cxx. . .


reader->SetFileName("subset.vtk");

reader->Update();

vtkContourFilter *iso = vtkContourFilter::New();

iso->SetInputConnection(reader->GetOutputPort());

iso->SetValue(0,0.26);

vtkPolyDataMapper *isoMapper = vtkPolyDataMapper::New();

isoMapper->SetInputConnection(iso->GetOutputPort());

isoMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *isoActor = vtkActor::New();

isoActor->SetMapper(isoMapper);

. . .

Code – Contour (isosurface)Code – Contour (isosurface)


Editor: isosurface.cxx. . .


reader->SetFileName(“density.vtk");

reader->Update();

vtkContourFilter *iso = vtkContourFilter::New();

iso->SetInputConnection(reader->GetOutputPort());

iso->SetValue(0,0.26);

vtkPolyDataMapper *isoMapper = vtkPolyDataMapper::New();

isoMapper->SetInputConnection(iso->GetOutputPort());

isoMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *isoActor = vtkActor::New();

isoActor->SetMapper(isoMapper);

. . .

Scalar GenerationScalar Generation Scalar Algorithms (cont)

– Scalar Generation• extract scalars from part of data• example: extracting z coordinate (elevation) from terrain data to

create scalar values

– VTK• vtkElevationFilter


Code – Scalar GenerationCode – Scalar Generation


Editor: hawaii.color.cxxvtkPolyDataReader *hawaii = vtkPolyDataReader::New();

hawaii->SetFileName("honolulu.vtk");

hawaii->Update();

hawaii->GetOutput()->GetBounds(bounds);

vtkElevationFilter *elevation = vtkElevationFilter::New();

elevation->SetInputConnection(hawaii->GetOutputPort());

elevation->SetLowPoint(0,0,bounds[4]);

elevation->SetHighPoint(0,0,bounds[5]);


lut->SetHueRange(0.7,0);

vtkDataSetMapper *hawaiiMapper = vtkDataSetMapper::New();

hawaiiMapper->SetInputConnection(elevation->GetOutputPort());

hawaiiMapper->SetLookupTable(lut);

vtkActor *hawaiiActor = vtkActor::New();

hawaiiActor->SetMapper(hawaiiMapper);

Scalar generation – Color MapScalar generation – Color Map


Editor: hawaii.color2.cxxvtkLookupTable *lut = vtkLookupTable::New();lut->SetNumberOfColors(9);lut->SetTableValue(0, 0.0, 0.40, 0.8, 1);lut->SetTableValue(1, 0.0, 0.75, 0.2, 1);lut->SetTableValue(2, 0.25, 0.625, 0.5, 1);lut->SetTableValue(3, 0.0, 0.5, 0.25, 1);lut->SetTableValue(4, 0.5, 0.365, 0.0, 1);lut->SetTableValue(5, 0.75, 0.625, 0.25, 1);lut->SetTableValue(6, 1.0, 0.75, 0.625, 1);lut->SetTableValue(7, 1.0, 0.75, 0.5, 1);lut->SetTableValue(8, 1.0, 1, 1, 1);

HedgehogsHedgehogs Vector Algorithms

– Hedgehogs • oriented scaled line for each vector• scale indicates magnitude• color indicates magnitude, pressure,

temperature, or any variable

– VTK• vtkHedgeHog


Code – HedgeHogsCode – HedgeHogs


Editor: hedgehog.cxxvtkStructuredGridReader *reader = vtkStructuredGridReader::New();


reader->Update();

vtkHedgeHog *hhog = vtkHedgeHog::New();

hhog->SetInputConnection(reader->GetOutputPort());

hhog->SetScaleFactor(0.001);

vtkPolyDataMapper *hhogMapper = vtkPolyDataMapper::New();

hhogMapper->SetInputConnection(hhog->GetOutputPort());

hhogMapper->SetLookupTable(lut);

hhogMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *hhogActor = vtkActor::New();

hhogActor->SetMapper(hhogMapper);

Oriented GlyphsOriented Glyphs Vector Algorithms (cont)

– Oriented Glyphs• orientation indicates direction• scale indicates magnitude• color indicates magnitude, pressure,

temperature, or any variable

– VTK• vtkGlyph3D


Code – Oriented GlyphsCode – Oriented Glyphs


Editor: glyph.cxxvtkArrowSource *arrow = vtkArrowSource::New();arrow->SetTipResolution(6);arrow->SetTipRadius(0.1);arrow->SetTipLength(0.35);arrow->SetShaftResolution(6);arrow->SetShaftRadius(0.03);

vtkGlyph3D *glyph = vtkGlyph3D::New();glyph->SetInputConnection(extract->GetOutputPort());glyph->SetSource(arrow->GetOutput());glyph->SetVectorModeToUseVector();glyph->SetColorModeToColorByScalar();glyph->SetScaleModeToDataScalingOff();glyph->OrientOn();glyph->SetScaleFactor(0.25);

vtkPolyDataMapper *glyphMapper = vtkPolyDataMapper::New();glyphMapper->SetInputConnection(glyph->GetOutputPort());glyphMapper->SetLookupTable(lut);glyphMapper->SetScalarRange(reader->GetOutput()->GetScalarRange());

Field LinesField Lines Vector Algorithms (cont)

– Field Lines• Fluid flow is described by a vector field in three dimensions for steady (fixed time)

flows or four dimensions for unsteady (time varying) flows• Three techniques for determining flow

– Pathline (Trace)• tracks particle through unsteady (time-varying) flow• shows particle trajectories over time• rake releases particles from multiple positions at the same time instant• reveals compression, vorticity

– Streamline• tracks particle through steady (fixed-time) flow• holds flow steady at a fixed time• snapshot of flow at a given time instant

– Streakline• particles released from the same position over a time interval (time-varying)• snapshot of the variation of flow over time• example: dye steadily injected into fluid at a fixed point


Field LinesField LinesStreamlines

• Lines show particle flow • VTK – vtkStreamTracer

Streamlets• half way between streamlines and glyphs• VTK - vtkStreamTracer, vtkGlyph3D

Streamribbon• rake of two particles to create a ribbon• VTK - vtkStreamTracer, vtkRuledSurfaceFilter

Streamtube• circular rake of particles to create a tube• VTK - vtkStreamTracer, vtkTubeFilter


Code – StreamlinesCode – Streamlines


Editor: streamLines.cxxvtkPointSource *seeds = vtkPointSource::New();seeds->SetRadius(3.0);seeds->SetCenter(reader->GetOutput()->GetCenter());seeds->SetNumberOfPoints(100);

vtkRungeKutta4 *integ = vtkRungeKutta4::New();

vtkStreamTracer *streamer = vtkStreamTracer::New();streamer->SetInputConnection(reader->GetOutputPort());streamer->SetSourceConnection(seeds->GetOutputPort());streamer->SetMaximumPropagation(100);streamer->SetIntegrationDirectionToBoth();streamer->SetIntegrator(integ);

vtkPolyDataMapper *mapStreamLines = vtkPolyDataMapper::New();mapStreamLines->SetInputConnection(streamer->GetOutputPort());mapStreamLines->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *streamLineActor = vtkActor::New();streamLineActor->SetMapper(mapStreamLines);

Code – StreamtubesCode – Streamtubes


Editor: streamTubes.varyRadius.cxxvtkPointSource *seeds = vtkPointSource::New();seeds->SetRadius(1.0);seeds->SetCenter(1.5, 0.01, 27);seeds->SetNumberOfPoints(50);

vtkRungeKutta4 *integ = vtkRungeKutta4::New();

vtkStreamTracer *streamer = vtkStreamTracer::New();streamer->SetInputConnection(reader->GetOutputPort());streamer->SetSourceConnection(seeds->GetOutputPort());…vtkTubeFilter *streamTube = vtkTubeFilter::New();streamTube->SetInputConnection(streamer->GetOutputPort());streamTube->SetRadius(0.01);streamTube->SetNumberOfSides(6);streamTube->SetVaryRadiusToVaryRadiusByScalar();

vtkPolyDataMapper *mapStreamTube = vtkPolyDataMapper::New();mapStreamTube->SetInputConnection(streamTube->GetOutputPort());mapStreamTube->SetScalarRange(reader->GetOutput()->GetScalarRange());

vtkActor *streamTubeActor = vtkActor::New();streamTubeActor->SetMapper(mapStreamTube);

AnnotationAnnotationAnnotation

– used for annotating visualization– VTK

• vtkScalarBarActor• vtkTextMapper• vtkScaledTextActor


Code – colorBarCode – colorBar


Editor: colorBar.cxxvtkStructuredGridReader *reader = vtkStructuredGridReader::New();reader->SetFileName("density.vtk");reader->Update();

vtkScalarBarActor *scalarBar = vtkScalarBarActor::New();scalarBar->SetLookupTable(lut);scalarBar->SetTitle("Combustor Density Magnitude");scalarBar->SetNumberOfLabels(2);scalarBar->GetPositionCoordinate()->SetValue(0.1, 0.01);scalarBar->SetOrientationToHorizontal();scalarBar->SetWidth(0.8);scalarBar->SetHeight(0.09);

vtkRenderer *ren1 = vtkRenderer::New();ren1->SetBackground(0.5,0.5,0.5);ren1->AddActor(streamTubeActor);ren1->AddActor(outlineActor);ren1->AddActor(scalarBar);

VTK - WritersVTK - Writers Polygonal Data Writers

– vtkBYUWriter - write MOVIE.BYU files– vtkCGMWriter - write 2D polygonal data as a CGM file– vtkIVWriter - write Inventor files– vtkMCubesWriter - write triangles in marching cubes format– vtkPolyDataWriter - write VTK polygonal data files– vtkPLYWriter - write Standford University PLY polygonal data files– vtkSTLWriter - write stereo-lithography files

Image and Volume writers– vtkBMPwriter - write PC bitmap files– vtkJPEGwriter - write images in JPEG format– vtkPostscriptWriter – write image files in Postscript format– vtkPNMwriter - write PNM (ppm, pgm, pbm) image files– vtkPNGwriter - write image file in Portable Network Graphic format– vtkTIFFWriter – write image files in TIFF format– vtkStructuredPointsWriter – write a vtkStructuredPoints file


Saving ImagesSaving ImagesSaving Images

– common formats:• jpeg (lossy)• png (lossless) • postscript• tiff (lossless)

– VTK•vtkWindowToImageFilter•vtkRenderLargeImage


Code – Saving ImagesCode – Saving Images


Editor: output.cxxvtkRenderer *ren1 = vtkRenderer::New();ren1->AddActor(streamTubeActor);ren1->ResetCamera();ren1->GetActiveCamera()->Dolly(1.25);ren1->ResetCameraClippingRange();

vtkRenderWindow *renWin = vtkRenderWindow::New();renWin->PointSmoothingOn();renWin->LineSmoothingOn();renWin->PolygonSmoothingOn();renWin->AddRenderer(ren1);renWin->SetSize(500,500);renWin->Render();

vtkWindowToImageFilter *w2if = vtkWindowToImageFilter::New();w2if->SetInput(renWin);

vtkTIFFWriter *writer = vtkTIFFWriter::New();writer->SetInputConnection(w2if->GetOutputPort());writer->SetFileName("image.tif");writer->Write();

vtkRenderLargeImage *renderLarge = vtkRenderLargeImage::New();renderLarge->SetInput(ren1);renderLarge->SetMagnification(4);

vtkTIFFWriter *lwriter = vtkTIFFWriter::New();lwriter->SetInputConnection(renderLarge->GetOutputPort());lwriter->SetFileName("./largeimage.tif");lwriter->Write();

VTK - ResourcesVTK - Resources


IS&T tutorials– Scientific Visualization Using VTK www.bu.edu/tech/research/training/tutorials/vtk/ – VTK Examples www.bu.edu/tech/research/training/scv-software-packages/vtk/vtk_examples/

Texts– The Visualization Toolkit, 4th Edition, Kitware, Inc, 2006.– The VTK User’s Guide, 5th Edition, Kitware, Inc, 2006.

Websites– www.vtk.org– www.kitware.com– www.vtk.org/doc/release/5.4/html/classes.html

Wiki– www.vtk.org/Wiki/VTK

Mailing Lists– www.vtk.org/VTK/help/mailing.html

http://www.bu.edu/tech/research/training/tutorials/vtk/

http://www.bu.edu/tech/research/training/scv-software-packages/vtk/vtk_examples/

Questions?Questions? Tutorial survey:

- http://scv.bu.edu/survey/tutorial_evaluation.html


http://scv.bu.edu/survey/spring11_tut_survey.html

scientific visualization using vtk

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