[email protected] 1 feature extraction and visualization of flow fields state-of-the-art report...
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1Feature Extraction and Visualization of
Flow [email protected]
State-of-the-Art Report
Feature Extraction and Visualization of Flow
FieldsFrits H. Post and Benjamin Vrolijk
Delft University of TechnologyThe Netherlands
visualisation.tudelft.nl{F.H.Post,B.Vrolijk}@its.tudelft.nl
Helwig Hauser, Robert S. Laramee, Helmut Doleisch
VRVis Research CenterAustria
www.VRVis.at{hauser,laramee,doleisch}@VRVis.at
Part 2:Feature-Based FlowViz
Part 1: Visualization of Flow Fields
2Feature Extraction and Visualization of
Flow [email protected]
Flow Visualization STAR Overview
Part 1: Visualization of Flow Fields
Introduction to Flow Visualization (FlowViz)
Direct FlowViz Texture-Based FlowViz Geometric FlowViz
Part 2: Feature-Based FlowViz
3Feature Extraction and Visualization of
Flow [email protected]
The FlowViz Job
Goal: communicating FlowViz data: data representing fluid/gas flow, i.e.
vector field data (magnitude + direction) not just scalar data visualization is a very high bandwidth
channel
User Goals: obtain overview of vector field present characteristics identify and investigate details and
features
4Feature Extraction and Visualization of
Flow [email protected]
Computational vs. Experimental and Empirical FlowVis
Computational FlowVis -using computers for FlowVis data resulting from flow simulation,
measurements, or flow modelling, e.g., computational fluid dynamics (CFD)
computer-generated images and animations, often mimicking experimental FlowVis
Visualization of actual fluids, e.g. water and air dye injection interferometry Schlieren/shadows flow topology graphs etc.
5Feature Extraction and Visualization of
Flow [email protected]
FlowVis Data vs. Data AcquisitionData from Simulation: FOR EACH cell in (irregular) grid: compute flow direction compute flow magnitude (explicitly or implicitly) compute pressure (à la Navier-Stokes equations) further attributes
Data from measurements: FOR EACH location of a (regular) grid: flow direction (reconstructed) measure flow magnitude
Data from modelling: Vector Field represented by analytic
function Flow direction and magnitude a
function of location (and time)
6Feature Extraction and Visualization of
Flow [email protected]
FlowViz Data Characterized by Many Dimensions
Spatial dimensions: 2D (planar flow, simplified or synthetic) 2.5D (boundary flow, flow on surface) 3D (real-world flow)Temporal dimension: steady flow -1 time step (or instantaneous flow) time-dependent flow -multiple time steps (turbulent,
real-world) caution is advised in the context of animationData dimensions: velocity temperature pressure and many more...
7Feature Extraction and Visualization of
Flow [email protected]
Direct vs. Geometric vs. Feature-Based FlowViz
focus on featuresmore detailed viewOverview, 1st impression
8Feature Extraction and Visualization of
Flow [email protected]
FlowViz Fundamentals
Flow Data from simulation: vector field represented as samples: vp,t (+ reconstruction)
v(p,t) = dp/dt; p,v Rn, t R
Flow Integration over Grids: Cartesian, curvi-linear, unstructured integration techniques: Euler and Runge-Kutta point location (which cell p lies in) and neighbor
searching flow reconstruction within a cell (à la
interpolation) computation of derived data
p(s) = p0 + v(p(), +t0) d [instantaneous]
pE(t+t) = p(t) + t v(p(t),t) [time-dependent]
9Feature Extraction and Visualization of
Flow [email protected]
Direct Flow VisualizationDirect Mapping of Flow Attributes to Visualization
Space
Advantages: simplicity less computation time intuitive
Disadvantages: does not always clearly
show flow properties and features, e.g., flow orientation
10Feature Extraction and Visualization of
Flow [email protected]
Direct FlowViz: Color Coded Slicing
Color Coding in 2D, instantaneous: mapping flow attribute(s) to hue
slicing probe for vortex visualization
(Schulz et al)
multiple slices for vortex visualization (missing color coded boundary)
11Feature Extraction and Visualization of
Flow [email protected]
Direct FlowViz: Arrow/Hedgehog plots in 2D and 3D, instantaneous
12Feature Extraction and Visualization of
Flow [email protected]
Direct FlowViz: Contours in 2D and isosurfaces in 3D
Contours in a slice
Isosurface (and color coding) in 3D
13Feature Extraction and Visualization of
Flow [email protected]
Direct FlowViz: Volume Rendering combined with color coding
the curvilinear bluntfin data set(Westermann)
14Feature Extraction and Visualization of
Flow [email protected]
Direct FlowViz: Hybrid Solutions -arrow plots and color coding in 2D, steady and
unsteady
15Feature Extraction and Visualization of
Flow [email protected]
Texture-Based Flow Visualization
Computing textures that provide a dense coverage/visualization of a vector field
Advantages: detailed view of vector field clearer perception of
characteristics contains elements of direct
+ geometric FlowViz
Disadvantages: computation
time 2.5D, 3D
16Feature Extraction and Visualization of
Flow [email protected]
Texture-Based FlowViz: Spot Noise (Van Wijk) and LIC (Cabral and Leedom) in 2D,
instantaneous
17Feature Extraction and Visualization of
Flow [email protected]
Texture-Based FlowViz: Spot Noise in 2D, instantaneous, with color coding (de Leeuw)
Good for visualizing detail.
18Feature Extraction and Visualization of
Flow [email protected]
Texture-Based FlowViz: Spot Noise and LIC in 2D, time-dependent (Van Wijk)
19Feature Extraction and Visualization of
Flow [email protected]
Texture-Based FlowViz: Time-Dependent Texture Advection in 2D
Unsteady FlowViz of the Gulf of Mexico (Jobard et al)
20Feature Extraction and Visualization of
Flow [email protected]
Texture-Based FlowViz: LIC on Surfaces, unsteady
A comparison of 3 LIC techniques (left) UFLIC, (middle) ELIC, and (right) PLIC (Verma et. al.)
21Feature Extraction and Visualization of
Flow [email protected]
Texture-Based FlowViz: LIC in 3D, instantaneous (Interrante and Grosch)
22Feature Extraction and Visualization of
Flow [email protected]
Geometric Flow Visualization
The computation of objects whose shape is directly related to underlying geometry
Advantages: intuitive clearer perception of
characteristics
Disadvantages: placement 3D
23Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Some Terminology
Stream vs. Path vs Streak vs Time lines
Streamline everywhere tangent to flow at
instantaneous time, t0 (blue/aqua)
Pathline path traced by a particle
over time, t (red/maroon)
Streakline line traced by continuous
injection at location, x0 (light green)
Timeline temporal evolution of initial
line, l0 (yellow)
24Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Streamlines and Streamlets in 2D, steady-state
25Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Pathlines and Streamlets in 2D, unsteady (Van Wijk)
26Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Timelines in 2D (Van Wijk) and 3D (B. Girod) (unsteady)
27Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Seeding in 2D (B. Jobard) and 3D (Schulz et al)
Image-based, topology-based, and interactive seeding strategies
28Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Streamribbons and Streamtubes, 3D, steady-state
29Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Perceptual Issues in 3D, steady-state
Illuminated Streamlines (Zoeckler)
StreamRunner (Laramee)
30Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Streaklines in 2D (Jobard et al) and 3D (B. Girod)
31Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: StreamBalls (Brill et al), StreamSurfaces (Hultquist),
StreamArrows (Loeffelmann et al), 3D, steady-state
32Feature Extraction and Visualization of
Flow [email protected]
Geometric FlowViz: Flow Volumes (Crawfis), steady and unsteady
A subset of 3D flow domain specified by initial 2D patch
33Feature Extraction and Visualization of
Flow [email protected]
Some Open Issues in FlowViz
Unsteady FlowViz on Surfaces -esp. Texture-based, unstructured
Steady-State FlowViz in 3D -perceptual issues, seeding strategies
Unsteady FlowViz in 3D -computation time
Lot’s of work to (still) be done.
34Feature Extraction and Visualization of
Flow [email protected]
Acknowledgements: Part 1
Thanks to (1) the KPlus (www.kplus.at) -Austrian governmental research program, and (3) AVL (www.avl.com) for financial support
For more information see: www.VRVis.at or email [email protected]
Now for Part 2!