scientific visualization : from data to insight · visualization : current challenges vijay...

Scientific Visualization : From Data to Insight

Vijay NatarajanIndian Institute of Science

Bangalore

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

What is Visualization?

» Visual representation of data (https://en.wiktionary.org/wiki/visualization)

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


Scientific Data

» Source: Simulations, measurement from imaging devices, sensing devices

» Focus: Scalar dataVijay Natarajan CSA Summer School, July 2017 5

NIR microscopy Density distribution in Silicium

CT / MRI

Electron microscopy

Atomistic simulations(Pore networks)

!

f :D"R

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 , …


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

Visualization : Current Challenges


» 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


• 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


IsosurfacePreimage of an isovalue: Isocontours and Isosurfaces

Source: Wikipedia


Scalar Field Visualization

Isosurfacing for Volume data

Foot from Visible Human Data [US NIH and NLM]

Isosurfaces


Isosurfaces


Isosurfaces

Isosurfaces


Isosurfaces


Isosurfaces

Isosurface Topology


Minimum

Maximum

Critical Points

Saddle

Saddle

Topological Structures : Reeb Graph

Reeb Graphs


Georges Henri Reeb

Contour Tree


» Loop-free Reeb graph

» Degree-1 and Degree-3

nodes

» How many trees with 1

minimum and 4 maxima?

» 1 minimum and 0 maxima?


Topological Structures as Abstract Representations

Highlight bones/organs via Reeb graph


Pore Networks from MS Complex

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

Mapping to the Volume

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

scalar volume


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



Simplification threshold = 0.005 Simplification threshold = 0.01

Simplification + Multiresolution

Input may contain noise or small-sized features

(Topological) Feature-directed Visualization


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


Application 2: Interactive Exploration of Time-Varying Data



Application 3: Segmentation


Reeb graph-directed surface segmentation


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]

Application 5: Symmetry in Scientific Data

» Detect similar subtrees within contour tree


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

5: Symmetry-aware transfer function design

Adenovirus Ribonucleoprotein Bacteriophage Flagella Bacteriophage


5: Symmetry-Aware Transfer Function Design


Acknowledgements


Visualization and Graphics LabIndian Institute of Science

" Department of Science and Technology, India

" Intel" Robert Bosch Centre for

Cyber-Physical Systems, IISc

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


based representations

: VGLIISc

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