Visualization 2003

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FocusContext TechniquesforNetwork Visualization
see www.visintuit.com later this week for
updated slides

• T. Alan Keahey
• keahey_at_visintuit.com

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FocusContext (FC) Techniques

• Basic Idea
• Show selected regions of interest in greater
  detail (focus)
• Preserve global view at reduced detail (context)
• NO occlusion
• All information is visible simultaneously

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Alternative Terms for FC

• Fisheye views
• Fisheye lens
• Continuously variable zoom
• Nonlinear magnification
• Hyperbolic views
• Distortion viewing
• Rubber sheet views

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Applications of FC

• Visualization of Networks/Graphs
• Viewing text
• Image/Document viewing
• Cartography
• Cluster Visualization

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Types of FC

• Spatial
• One Dimensional
• Easy to apply and understand
• Two Dimensional
• Most common, operating on 2D layouts of
  information
• Three Dimensional
• Less common
• Logical
• Effect applies to logical structure of the
  information
• Combined Spatial and Logical
• Data Driven Magnification

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1D Single Axis FC

• Fisheye Views of Text Files
• Vertically stretch/compress lines of text
• S. Greenberg, C. Gutwin, and A. Cockburn.
  Awareness through fisheye views in relaxed
  WYSIWIS groupware. In Proceedings of Graphics
  Interface, May 1996.
• TreeJuxtaposer
• Layout large hierarchies along a single dimension
  and stretch/compress as needed
• T. Munzner et al, TreeJuxtaposer Scalable tree
  comparison using FocusContext with guaranteed
  visibility, SIGGRAPH 2003. (also in InfoVis 2003
  Contest Posters)

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2D General Approaches

• 2D nonlinear transformations
• Mappings to Hyperbolic Space
• Projections of 3D surfaces to 2D

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2D Perspective Wall

• Map information onto a 3 panel wall.
• Project into 2D visual space
• Information in central panel is larger than on
  sides
• J.D. Mackinlay, G.G. Robertson, and S.K. Card.
  The perspective wall Detail and context smoothly
  integrated. In Proceedings of the ACM Conference
  on Computer Human Interaction, pages 173-179,
  1991.

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2D Document Lens

• Extend Perspective Wall concept to a 5 Panel
  Display
• Better use of available space than perspective
  wall
• G. Robertson and J. D. Mackinlay. The document
  lens. In Proceedings of the ACM Symposium on User
  Interface Software and Technology, pages 101-108,
  1993.

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2D Fisheye Views

• 2D layout via a 1D magnification function
• lets user vary the degree of magnification
• Magnification applies to entire graph
• Manojit Sarkar, Scott S. Snibbe, Oren Tversky,
  and Steven P. Reiss. Stretching the rubber sheet
  A metaphor for visualizing large layouts on small
  screens. In Proceedings of the ACM Symposium on
  User Interface Software and Technology, 1993.

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2D Hyperbolic Space

• Map the network layout in Euclidean space into
  Hyperbolic space
• Objects at center of space are large
• Infinite space at periphery
• But at infinitely reduced scale
• Effect is a global focuscontext display

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2D Hyperbolic Tree

• Commercial product from Inxight
• (Xerox PARC spinoff)
• Selected node becomes center of display
• Other sections shown at reduced resolution
• John Lamping, Ramana Rao, and Peter Pirolli. A
  focuscontext technique based on hyperbolic
  geometry for visualizing large hierarchies. In
  Proceedings of the ACM Conference on Computer
  Human Interaction, 1995.

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2D HyperLINK Graph Visualization

• View a graph network representing WWW navigation
• Magnification centers on the current node
• T. Alan Keahey and Reid Rivenburgh. HyperLINK A
  program for visualizing traversal of the WWW. ACM
  Conference on Hypertext, March 1996.

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2D Nonlinear Magnification

• Mathematical generalization of focuscontext
  techniques
• Direct representation of 2D transformations
• x, y t(x, y)
• Allows constrained, multiple centers of
  magnification
• T. Alan Keahey and Edward L. Robertson.
  Techniques for non-linear magnification
  transformations. In Proceedings of the IEEE
  Symposium on Information Visualization, pages
  38-45, October 1996.

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2D Distortion Viewing

• Map 2D information onto a hilly surface
• View surface from above
• Higher surfaces generally larger than lower
  surfaces, except at regions of slope
• T(x, y, z) x, y
• M.S.T. Carpendale, D. Cowperthwaite, and
  D. Fracchia. 3D pliable surfaces For the
  effective presentation of visual information. In
  Proceedings of the ACM Symposium on User
  Interface Software and Technology, pages 217-226,
  1995.

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3D General Approaches

• Perspective view-based
• Nearer information is larger
• Hyperbolic Space Mapping
• Extension of 2D hyperbolic mapping
• 3D Nonlinear Transformation
• Direct extension of 2D transformation
• Distortion Tunnels
• Use transformation to open holes into 3D
  information

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3D Cone Trees

• Layout tree networks with a 3D cone representing
  each stage in a hierarchy
• Top root node
• Bottom leaf nodes
• Rotate cones to bring items of interest nearer
• G.G. Robertson, J.D. Mackinlay, and S.K. Card.
  Cone trees Animated 3d visualizations of
  hierarchical information. In Proceedings of the
  ACM Conference on Computer Human Interaction,
  pages 189-194, 1991.

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3D Hyperbolic Space

• Site Manager (SGI)
• View spanning tree of large graphs
• Show networks of 60,000 nodes
• Visible structure dynamically updates to reflect
  viewing settings
• Tamara Munzner. H3 Laying out large directed
  graphs in 3D hyperbolic space. In Proceedings of
  the IEEE Symposium on Information Visualization,
  IEEE Visualization, October 1997.

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3D Cluster Visualization

• Based on 3D version of Nonlinear Magnification
• Expand clusters of data points in a sparse space
• T. Alan Keahey. Visualization of high-dimensional
  clusters using nonlinear magnification. In Visual
  Data Exploration and Analysis VI, volume 3643 of
  SPIE, January 1999.

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3D Distortion Tunnels

• Use a nonlinear transformation to push items out
  of the line of sight
• Removes occluding items
• allows view directly into the middle of the view
  field
• D. Cowperthwaite, M.S.T. Carpendale, and
  D. Fracchia. Visual access for 3D data. In
  Proceedings of the ACM Conference on Computer
  Human Interaction, 1996. Short paper.

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Logical FC

• Structured Text Files
• Collapse/Expand sections of text (source code)
• George W. Furnas. Generalized fisheye views.
  Human Factors in Computing Systems, CHI '86,
  pages 16-23, April 1986.
• Nested Networks
• Pre-layout calculation of FC Effects
• Emanuel G. Noik. Layout-independent fisheye views
  of nested graphs. In IEEE Symposium on Visual
  Languages, pages 336-341, August 1993.
• Zippers Logical Web Pages
• Show sections of web pages based on HTML
  structure
• Marc H. Brown, Hannes Marais, Mac A. Najork, and
  William E. Weihl. Focuscontext display of web
  pages Implementation alternatives. In
  Proceedings of the 6th International World Wide
  Web Conference, April 1997.

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SpatialLogical FC

• General Problem
• How to synchronize spatial and logical
  transformations?
• Many specialized solutions
• General Solution
• Nonlinear Magnification Fields
• Show degree of magnification for any spatial
  transformation
• T. A. Keahey and E. L. Robertson. Nonlinear
  magnification fields. IEEE Information
  Visualization, 1997.

transformation
combined
magnification
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SpatialLogical FC

• SHRIMP Views
• Software Visualization and Debugging
• M.-A. D. Storey, K. Wong, F.D. Fracchia, and H.A.
  Muller. On integrating visualization techniques
  for effective software exploration. In
  Proceedings of the IEEE Symposium on Information
  Visualization, IEEE Visualization, 1997.
• H3
• Compute visible graph to render network based on
  hyperbolic mapping
• Tamara Munzner. H3 Laying out large directed
  graphs in 3D hyperbolic space. In Proceedings of
  the IEEE Symposium on Information Visualization,
  IEEE Visualization, October 1997.
• Interactive Travel Atlas
• Levels of Detail for items on a map
• T. Alan Keahey and Edward L. Robertson. Nonlinear
  magnification fields. In Proceedings of the IEEE
  Symposium on Information Visualization, IEEE
  Visualization, October 1997.

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Data Driven Magnification

• Use properties of the data to define a
  magnification for viewing it
• Air Traffic Control
• Continuous Cartograms
• T. Alan Keahey. Area-normalized thematic views.
  In Proceedings of International Cartography
  Assembly, August 1999.

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Potential Limitations of FC

• Limited degree of magnification?
• 10X Maximum?
• Open research question
• Disorientation
• Complex transformations might cause viewer to get
  lost
• Need effective visual cues to avoid this

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Alternatives to FC

• PanZoom
• Scales to high factors
• Navigation can be a problem
• Multiple views at different scales
• No distortion between scales
• No continuity either

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Strengths of FC

• Mirrors the way the visual cortex is designed
• Good navigation tool for interactively exploring
  data
• probe regions of interest before committing to
  navigating to them (easily reversible)
• Can be combined with other viewing paradigms such
  as Pan and Zoom

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For More Information

• Updated version of course slides
• www.visintuit.com (later this week)
• General Information about FocusContext
• Nonlinear Magnification InfoCenter
• www.cs.indiana.edu/tkeahey/nlm/nlm.html