Comp/Phys/APSc 715 Vector Fields: Particle Systems, Streamlines, - - PDF document

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Comp/Phys/APSc 715 Vector Fields: Particle Systems, Streamlines, - - PDF document

2/18/2014 Comp/Phys/APSc 715 Vector Fields: Particle Systems, Streamlines, Streaklines, Rakes, Ribbons, Glyphs, Textures, Color 2/18/2014 Vector Comp/Phys/APSc 715 Taylor 1 Example Videos Bdvis: Hentsche Vis 2008 Paper_1038_movie:


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Vector Fields: Particle Systems, Streamlines, Streaklines, Rakes, Ribbons, Glyphs, Textures, Color

Comp/Phys/APSc 715

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Example Videos

  • Bdvis: Hentsche Vis 2008
  • Paper_1038_movie: Johnson Vis 2008
  • Vis2008: Mayerich Vis 2008

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Administrative

  • Homework Grading:

– Remember to put the PNG files into Zip – Remember to put final design image into Zip

  • Homework Schedule:

– Homework 2 deadline moved to Thursday – Homework 3 will be done in class Tuesday – Homework 4 in the making

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  • See movement of fluid in an instant or over time

– Steady state

  • flow field static over visualization

– Unsteady state

  • flow field changes over time
  • Application areas

– Aerodynamics, CAD, airflow through/around buildings,

  • cean currents, fluid flow through pumps/valves,

electromagnetics

Vector/Flow Visualization Goals

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Example Vector Fields

  • From Rex Abert at FSU
  • Flow with two centers,

rotating in opposite

  • directions. Between the

centers, the flow is to the right.

http://www.csit.fsu.edu/~rabert/vfresearch/images.html

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Example Vector Fields

  • From Rex Abert at FSU
  • Flow with two centers,

rotating in the same

  • direction. This produces a

saddle point between the two centers. Flow around the centers is counter- clockwise.

http://www.csit.fsu.edu/~rabert/vfresearch/images.html

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Example Vector Fields

  • From Rex Abert at FSU
  • Flow with two sinks,

producing a saddle between.

http://www.csit.fsu.edu/~rabert/vfresearch/images.html

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Example Vector Fields

  • From Rex Abert at FSU
  • Flow with a source and a

sink, producing no saddle between.

http://www.csit.fsu.edu/~rabert/vfresearch/images.html

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Vector Visualization Questions (Write these on board)

  • Where are critical points in a flow field?

– Sources, sinks – Centers of rotation, Vortices (tornadoes) – Fastest flow, stationary (saddle) points

  • What is the shape of a flow field?

– Where is a flow laminar, where is it turbulent? – Where is there rotation in a flow?

  • Where will an object released into a field end up?
  • Where did a concentration (e.g. CO) come from?
  • Where does stress cause strain on an object?

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Vector Visualization Techniques

  • Advected particles and their trails

– Particle systems – Streamlines

  • Streaklines
  • Rakes
  • Glyphs

– Arrows, tufts, etc.

  • Textures

– Line-integral convolution, Dye advection

  • Surfaces

– Stream Surfaces, Streak Surfaces – Deformation of geometric shapes

  • Color

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Particle Systems

  • “Smoke puffs” released into the field

– Massless particles “go with the flow” – Displayed through animation

  • Advection method

– In single time step vs. over multiple time steps

  • Release pattern

– Sphere, flat spray, line, grid, etc. – One-time, continuous, bursts

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Particle Systems Example 2

  • Mickail Teverovskiy and Ica Manas-

Zloczower,Case Western Reserve University

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Particle Systems Example 3

  • http://www-vis.lbl.gov/Vignettes/
  • P.Nugent, D.Kasen, LBNL
  • Supernova simulation

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Particle Systems Example 4

  • http://www-vis.lbl.gov/Vignettes/
  • R. Ryne and J. Qiang, LBNL
  • Simulation

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Particle Systems Example 5

  • http://www-

vis.lbl.gov/Vignettes/

  • J. Primack, Thomas Cox,

UCSC

  • Simulation

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Particle Characteristics

  • Benefits

– Show advection directly – Cluster motion shows critical points and features of the flow – Motion shows where particles end up

  • Difficulties and Issues

– Occlusion and confusion with lots of particles – Hard to remember where particles came from

  • Run in reverse!

– Placement and timing of release

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Streamlines and Their Kin

  • “Streaks” left by particle traces, simulations of smoke

trails in wind-tunnel experiments

  • Geometry

– Lines, illuminated lines, tubes, ribbons

  • Advection method

– Single time: Called streamlines – Over time: Called streaklines (look the same)

  • Release pattern

– Single, rakes, grids, etc.

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Streamlines

  • Turk and Banks
  • SIGGRAPH 1996
  • Placement and spacing matters

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Streamline Examples

  • Anna Turnage, IEEE CG&A Vol 2 No 3, 2002. Pp. 16-21

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Rainbow

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SLIDE 8

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Why Transparent and Illuminated

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Short Streamlines (1)

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http://earthobservatory.nasa.gov

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Short Streamlines (2)

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http://earthobservatory.nasa.gov

  • Tube = surface at constant distance from streamline
  • 3D entities for improved perception
  • Auxiliary information display

– can color to show value – can vary radius to show value

Tubes

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Tubes Example

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Rainbow

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Tubes Example 2

  • C.R. Johnson, R.S.

Macleod, and M. Matheson, Univ. of Utah

  • Electric Current in

Thorax

– Colored by polarity

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Tubes Example 3

  • Greg Schussman and Kwan-Liu Ma, 2002

– UC Davis

  • Electric field

– Blue

  • Magnetic

– Orange

  • Simulation

– Accelerator

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Tubes Example 4

  • Interactive volume rendering of thin thread

structures within multivalued scientific data sets: Wenger, Keefe, Zhang & Laidlaw 2004

  • Velocity (Ylw,Grn)
  • Vorticity (Ppl,Pnk)
  • Halos
  • Volume Rendered

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Ribbons

  • Advected line plus twist of the line
  • Matlab example:
  • Reveals twist

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Ribbon Example: NCSA

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Ribbon Examples

  • Anna Turnage, IEEE CG&A Vol 2 No 3, 2002. Pp. 16-21

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Rainbow

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1D Rake

  • NASA Ames Virtual Wind Tunnel
  • Lines seeded uniformly along a line

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Rainbow

Streamlines and other effects

  • Vis 2004, Xue et. al. (Link to movie)

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Streamline Characteristics

  • Benefits

– Show advection directly – Cluster motion shows critical points and features of the flow – Shows where flows go, and where they came from – Can show twist (with ribbons) as well as advection

  • Difficulties and Issues

– Occlusion and confusion with lots of lines – Which direction is the flow? – Placement of release

  • show off interesting features
  • even spacing in merging/diverging fields

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Glyphs

  • Placing individual icons scattered in the field

– Features of icons reveal information about the field

  • Some techniques

– Arrows / hedgehog / tufts – Tensor glyphs (flow probes)

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The Real Thing

  • U.S. Air and Space Museum near Dulles

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Arrows

  • http://www.cs.utah.edu/~cs5630/examples/arrows.html

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Rainbow

Arrows Along a Rake

  • NASA Ames Virtual Wind Tunnel

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Tufts

  • Style used by Edmund Halley (1696)

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Straight-line Glyphs

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Curved-line Glyphs

  • Turk and Banks, SIGGRAPH 1996

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Flow Probe

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Tubes and Flow Probes

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Arrow Placement

  • Ware: Aligned head-to-tail perceived as flow

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Arrow Placement 2

  • Turk and Banks, SIGGRAPH 1996

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GlyphSea

  • Amit Chourasia, et. al., SDSC

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Rainbow

Flow RADAR Glyphs

  • Hlawatsch, Leub, Nowal, Weiskopf; TVCG 2011

– Summarizes flow direction over time – Beginning of time is at the center (less accurate)

  • Can invert if flow at start matters more

– Color shows speed – Uncertainty range

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Use for spatial summary? Rainbow

Glyph Characteristics

  • Benefits

– Show complicated structure at each glyph location

  • Difficulties and Issues

– Difficult to use densely in 3D (due to occlusion)

  • Consider modulating presence based on scalar field

– Size (smaller sampling vs. larger to show more info) – Placement

  • Regular vs. flow-following
  • Analysis of topology
  • Interactive probing

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Textures

  • Construct a texture that shows the field
  • Techniques

– Line-Integral Convolution (LIC) – Spot Noise – Reaction-Diffusion – Dye Advection

  • Additions

– Animation – 3D volume (doesn’t work as well, but halos help a lot)

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2D Animated LIC Example

  • From H.W. Shen, Univ. of

Utah

  • 2D line-integral convolution

visualization of a vector field

  • http://www.cs.utah.edu/~cs

5630/examples/lic.html

  • (Video – click on it)
  • Link

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Oriented “LIC” (spot noise)

  • Flow direction indicated by anisotropic splats

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Rainer Wegenkittl and Eduard Groller, 1997

3D LIC with and without Halos

  • http://www-users.cs.umn.edu/~interran
  • Victoria Interrante, Visualization 1997
  • Link

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3D LIC plus color (1)

  • Victoria Interrante
  • Both images have halos

Color from red to yellow with +Temp +Saturation with +Streamwise vorticity

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3D LIC plus color (2)

  • http://www-users.cs.umn.edu/~interran/3Dflow.html
  • Victoria Interrante
  • Color shows magnitude of vorticity
  • No halos

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3D Seed LIC (volume rendered)

  • Helgeland & Andreassen TVCG 2004.

– Input textures in white

  • ROI from vorticity mag.

– Top: 9528 seeds – Bottom: 20,724 seeds – “Limb darkening”

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2D Spot Noise

  • http://www.cwi.nl/~wimc/spotnoise.html
  • Wim de Leeuw

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Rainbow

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2D Spot Noise on Slices

  • http://www.cwi.nl/~wimc/spotnoise.html
  • Wim de Leeuw
  • 2D LIC in 3D

– On sphere – On slice

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Rainbow

Reaction-Diffusion

  • Vis 2004: Sanderson, Johnson, Kirby

– Adjusting reaction rate changes size – Anisotropic diffusion causes stretching – Touch up

  • Lightdark
  • Direction

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2004 Sanderson, Johnson, Kirby

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2004 Sanderson, Johnson, Kirby

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2004 Sanderson, Johnson, Kirby

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Dye Advection

  • Sea Currents

– Gulf of Mexico

  • Jobard et al., IEEE Trans V&CG, 8(3)

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Dye Advection 2

  • Flow around a circular cylinder
  • Jobard et al., IEEE Trans V&CG, 8(3)

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Transport and Anisotropic Diffusion

  • Burkle, Preuber, Rumpf, Vis 2001.

68

Rainbow

Complete Texture System

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3D Texture System

  • Vis 2004, Xue et. al. (Link to video)

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The Real Thing

  • NASA Landsat image off Chilean coast

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Texture Characteristics

  • Benefits

– Shows entire field (at least in 2D) – Can animate entire field – Shows critical points

  • Difficulties and Issues

– Hard to show in 3D, due to occlusion – Hard to get quantitative information

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Stream Surfaces

  • “Thick” lines within plane
  • r surfaces within volume

that show results of flow

  • Stream surfaces show
  • utline of region where

an initial line (in 2D) or polygon (in 3D) is swept in flow

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Stream Surfaces

  • Surface swept by patch
  • Implementation 1:

– generate stream lines – join adjacent streamlines to form triangles – Issue: diverging and merging flows

  • Implementation 2:

– Inject “ink” patch at boundary – Advect the ink through field – Generate ink isosurface

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Stream Surfaces

  • Helman and Hesselink, Stanford University

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Separating Streak Surfaces (1)

  • Ferstl, Burger, Theisel, Westermann; TVCG 2010

– Separating surfaces on a torus and cylinder

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Separating Streak Surfaces (2)

  • Ferstl, Burger, Theisel, Westermann; TVCG 2010

– Red separating surface vs. green time-release planes

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Surface Characteristics

  • Benefits

– Shows where initial concentration ends up

  • Difficulties and Issues

– Show only a subset of the field – Significant divergence makes surface large – Occlusion can be a problem

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  • Color as auxiliary

– Usually magnitude – May be age, release location, or other

  • Interactive color

– Boring and Pang, Vis ‘96 – hue to show relationship between vec and light – interactive exploration

Color

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  • Color wheel

– Johansen and Moorhead, CG&A ‘95 – color angle (hue) shows orientation – optionally, magnitude as saturation and/or lightness

Color Wheel

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Colorwheel Example

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Color to disambiguate direction

  • PNNL: Wong, Foote, Kao, Leung, Thomas

84

Rainbow

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Pattern Matching Color

  • Julia Ebling, “Clifford Convolution And Pattern Matching

On Vector Fields”, Vis 2003

– Select canonical field shape – Find local best orientation – Dot-product-like sum – Produces scalar field

85

Rainbow

Ebling Vis2003 Matching in 3D

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Color Characteristics

  • Benefits

– Can show data over the whole field – Color good for nominal labeling (release location, age) – Color good to overlay scalar data set (magnitude, pressure)

  • Difficulties and Issues

– Mapping direction to color is unnatural – Mapping direction + magnitude loses resolution

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Comparison

  • Vis 2004: Laramee: laramee.mpg

– Different flow visualization techniques – http://cs.swan.ac.uk/~csbob/research/swirl- tumble/video/larameeVis04investigating.mpg

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Combination of Techniques

  • Using: Iris Explorer (sold by NAG)
  • By: Lutz Justen
  • Streamlines
  • Arrow glyphs

– Show direction

  • LIC-like texture
  • Color (magnitude)

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Same colors 2 meanings

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Combo: Virtual Wind Tunnel

Steve Bryson NASA Ames Streamlines Rakes Color Isosurfaces Cut Plane Model

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Rainbow

Combo: LIC and Velocity Mask

  • Sea Currents

– Gulf of Mexico

  • Jobard et. al.

– IEEE Trans V&CG

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Combo: LIC and Velocity Mask

  • Cyclone formation

– Europe

  • Jobard et. al.

– IEEE Trans V&CG

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Combo: LIC and Saddle Connectors

  • Vis 2003: Theisel, Weinkauf, Hege, Seidel

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Summary (2008)

P S G T Ss C Questions L Y Y G L/ T Y Where are critical points in

a flow field?

G Y Y G

What is the shape of a flow field?

L 50 Y L 50

Where will an object released into a field end up?

T+ T G 50

Where did a concentration (e.g. CO) come from?

Y = yes, + = really good, L = if you’re lucky, T = with tricks, 50 = directional ambiguity

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Summary (2005)

Par Li Gl

Tex

Sfc Clr L L+ Ok

Ok

X X Sources and sinks Ok Tr Ok

Ok

X Ok Fast/slow/still Ok L Ok Ok X X Center of rotation Ok + Ok Ok X X Shape of flow Ok ++ ?

Ok

X X Where is flow laminar vs. turbulent? ++ T L

Dye

L X Where would a pushed object end up? T T L T

L

X Where does a concentration come from? Ok Ok Ok ? + X Where does stress cause strain? T T Ok T T ++ Positive vs. negative field (scalar)? L=If you’re lucky, += Real good, T=With tricks

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Summary (from 2003)

P~ L~ G

T2+

S~ C* Where are sources and sinks? P L G

T2+

S~ C* Where is flow laminar vs. turbulent? P~ L~ G~

T2+

Center of rotation P La G+ Ta Local flow direction P~ G~ Th C Where is flow fastest? P+ La G~ T*

S

Where would a pushed object end up? P* La G~ T* S Where does a concentration come from? P L~ G~

T2+

C* Where are stationary points? N G C Positive vs. negative field (scalar)? ~=If you’re lucky, += Real good, *=With tricks, 2=2D, a= ambiguity, h=hard Particle, Lines, Glyph (answers for 2D), Texture, Surface, Color

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Summary (from 2002)

P+ L G+ T2 Where are sources and sinks? Where is flow laminar vs. turbulent? P L G

T2+

Where is rotation in flow? P L G Where is twist in 3D flow? P L G~ Where is vertex core in 3D flow? P L+ G

T2+

Where are saddles? P G* T S~ C Where is flow fast vs. slow? P+ L~ G T2

S~

Where would a pushed object end up? P L+ G T S+ Where does a concentration come from? P G+ T S Direction of flow (along a surface)? P~ g T Where are stationary points? G C Positive vs. negative field (scalar)? ~=If you’re lucky, += Real good, *=With tricks, g=small dense glyphs, 2=2D Particle, Lines, Glyph, Texture, Surface, Color

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Credits

  • This lecture is based on a lecture given by Penny

Rheingans at University of Maryland Baltimore County, for course CMSC 491B/691B.

  • Flow Probe: Wijk, J.J. van, A.J.S. Hin, W.C. deLeeuw,

F.H. Post, “Three Ways to Show 3D Fluid Flow.” IEEE Computer Graphics and Applications, vol. 14, no. 5,

  • p. 33-39, September 1994.
  • Stream Surfaces: CJM. Lasance, Philips Research

(found on http://www.electronics- cooling.com/html/1999_jan_article3.html).

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Credits

  • Arrows, Streamline Example: Jean M. Favre, GWU.
  • Tufts, Arrow Placement, Colin Ware, “Information

Visualization”

  • Noise-based advection with velocity mask, Dye

advection: Jobard et. al. “Lagrangian-Eulerian Advection of Noise and Dye Textures for Unsteady Flow Visualization,” IEEE Trans. Vis. & Comp. Gfx. 8(3), July-Sept 2002.

  • Others: As listed on slides.

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