Scientific Visualization : From Data to Insight Vijay Natarajan - - PowerPoint PPT Presentation

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Scientific Visualization : From Data to Insight Vijay Natarajan Indian Institute of Science Bangalore What is Visualization? http://en.wikipedia.org/wiki/Visualization Creative Visualization Creative Visualization is the

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Scientific Visualization : From Data to Insight

Vijay Natarajan Indian Institute of Science Bangalore

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What is Visualization?

» http://en.wikipedia.org/wiki/Visualization

» Creative Visualization » “Creative Visualization is the cognitive process of purposefully generating visual mental imagery, with eyes open or closed …” » … day dreaming

Vijay Natarajan CSA Summer School, July 2017 3

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What is Visualization?

» Visual representation of data

(https://en.wiktionary.org/wiki/visualization)

» Data ! Pictures » Scientific Visualization » Scientific (Data) Visualization

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Scientific Data

» Source: Simulations, measurement from imaging devices, sensing devices » Focus: Scalar data

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NIR microscopy

Density distribution in Silicium

CT / MRI Electron microscopy Atomistic simulations (Pore networks)

! f : D "R

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Scientific Data Visualization

» Aim: Study and develop methods to

" Understand underlying phenomena " Communicate (research) findings

» Application domains

" medical imaging " x-ray crystallography " structural biology " computational fluid dynamics " climate science " material science " geology, cosmology , …

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CSA Summer School, July 2017 #7

Visualization Pipeline

[dos Santos, S. and Brodlie, K., Gaining understanding of multivariate and multidimensional data through visualization, Computers & Graphics, 28(3), 311–325, 2004.]

Vijay Natarajan

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Visualization : Current Challenges

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» Large data sizes » Feature-rich data » Integrated analysis and visualization

" Visual abstractions " Intuitive exploration

[Doraiswamy and Natarajan, IEEE Trans. Visualization and Computer Graphics, 2013] vacet.sci.utah.edu

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Surface plot
interpret scalar value as height
Color mapping
assign a color to scalar values
Contour plot
extract curves as pre-image of

given scalar value

Scalar Field Visualization - 2D

! f : R2 "R

Source: Wikipedia

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Isosurface

Preimage of an isovalue: Isocontours and Isosurfaces

Source: Wikipedia

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Scalar Field Visualization

Isosurfacing for Volume data

Foot from Visible Human Data

[US NIH and NLM]

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Isosurfaces

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Isosurfaces

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Isosurfaces

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Isosurfaces

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Isosurfaces

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Isosurfaces

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Isosurface Topology

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Minimum Maximum Critical Points Saddle Saddle

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Topological Structures : Reeb Graph

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Reeb Graphs

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Georges Henri Reeb

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Contour Tree

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» Loop-free Reeb graph » Degree-1 and Degree-3 nodes » How many trees with 1 minimum and 4 maxima? » 1 minimum and 0 maxima?

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Topological Structures as Abstract Representations

Highlight bones/organs via Reeb graph

[Doraiswamy and Natarajan, IEEE Trans. Visualization and Computer Graphics, 2013]

Pore Networks from MS Complex

[Gyulassy, Natarajan, et al. IEEE Trans. Visualization and Computer Graphics, 2007]

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Mapping to the Volume

» Arcs in Reeb graph map to cylinders in domain » Use Reeb graph as an abstract interface into scalar volume

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Computing Reeb Graph

» Split-and-compute strategy (2011)

10 times faster than earlier methods
4-6 million elements in 4-6 sec

» Parallel algorithm (2015)

8.6 billion points in 3 min on 64 cores
Requires 10GB only

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Simplification threshold = 0.005 Simplification threshold = 0.01

Simplification + Multiresolution

Input may contain noise or small- sized features

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(Topological) Feature- directed Visualization

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Application 1: Transfer Function Design

Topology controlled volume rendering

[Weber et al., IEEE TVCG 2007]

Spatially aware transfer function design

[Doraiswamy and Natarajan, IEEE TVCG 2011]

Movie at 2x

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Application 2: Interactive Exploration of Time-Varying Data

[Doraiswamy and Natarajan, IEEE Trans. Visualization and Computer Graphics, 2011]

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Application 2: Interactive Exploration of Time-Varying Data

[Doraiswamy and Natarajan, IEEE Trans. Visualization and Computer Graphics, 2011]

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Application 3: Segmentation

[Doraiswamy and Natarajan, IEEE Trans. Visualization and Computer Graphics, 2011]

Reeb graph-directed surface segmentation

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Application 4: Isosurface Selection

Extracting and tracking cloud systems

[Doraiswamy, Natarajan, and Nanjundiah. IEEE Trans. Visualization and Computer Graphics, 2013]

Flexible isosurfaces

[Carr et al., IEEE VIS 2004]

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Application 5: Symmetry in Scientific Data

» Detect similar subtrees within contour tree

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[Thomas and Natarajan, Symmetry in scalar field topology, IEEE TVCG 2011]

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5: Symmetry-aware transfer function design

Adenovirus Ribonucleoprotein Bacteriophage Flagella Bacteriophage

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5: Symmetry-Aware Transfer Function Design

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Acknowledgements

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Visualization and Graphics Lab Indian Institute of Science " Department of Science and Technology, India " Intel " Robert Bosch Centre for Cyber-Physical Systems, IISc

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Summary

» Challenges in visualization » Feature-directed visualization » Abstract / topology-based representations » Efficient computation of topological structures

" Parallel (GPU / Hybrid) algorithms " Memory efficient

» New applications!! » Webserver and libraries at http://vgl.csa.iisc.ac.in

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based representations

: VGLIISc