1 h3: laying out large directed graphs in 3d hyperbolic space andrew chan cpsc 533c march 24, 2003
TRANSCRIPT
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Ideas behind H3
Creating an optimal layout for a general graph is tough
Creating an optimal layout for a tree is easier
Often it is possible to use domain-specific knowledge to create a hierarchical structure from a graph
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Stumbling Blocks
The deeper the tree, the more nodes; exponential growth
You can see an overview, or you can see fine details, but not both
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Solution
A layout based on hyperbolic space, that allows for a focus + context view
H3 used to lay out hierarchies of over 20 000 nodes
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2D Graph and Tree Drawing
Thinking very small-scale Frick, Ludwig, Mehldau created
categories for graphs; # of nodes ranged from 16 in the smallest category, to > 128 in the largest
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2D Tree Drawing (cont’d)
MosiacG SystemZyers and Stasko
Image from:http://www.w3j.com/1/ayers.270/paper/270.html
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3D Graph Drawing (cont’d)
Other work centered around the idea of a mass-spring system– Node repel one another, but links
attract– Difficulty in converging when you try
to scale the systems Aside: Eric Brochu is doing similar
work in 2D - http://www.cs.ubc.ca/~ebrochu/mmmvis.htm
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3D Tree Drawing
Cone Trees, Robertson, Mackinlay, CardImage from: http://www2.parc.com/istl/projects/uir/pubs/items/UIR-1991-06-Robertson-CHI91-Cone.pdf
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Hyperbolic Focus+Context
Hyperbolic Tree Browser,
Lamping, Rao
Image from:
http://www.acm.org/sigchi/chi95/Electronic/documnts/papers/jl_figs/strip1.htm
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Alternate Geometry
Information at: http://cs.unm.edu/~joel/NonEuclid/
Euclidean geometry– 3 angles of a triangle add up to?– Shortest distance between two points?
Spherical geometry– How we think about the world– Shortest way from Florida to Philippines?
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Alternate Geometry (cont’d)
Hyperbolic Geometry / Space– Is important to the Theory of Relativity– The “fifth” dimension– Can be projected into 2-D as a pseudosphere
– Key: As a point moves away from the center towards the boundary circle, its distance approaches infinity
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Finding a Tree from a Graph
Most effective if you have domain-specific knowledge
Examples:– File system– Web site structure– Function call graphs
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Tree Layout
Cone tree layout versus H3 Layout
Image from: http://graphics.stanford.edu/papers/h3/html/node12.htm#conefig
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Sphere Packing
Need an effective way to place information
Cannot place spheres randomly Want to have a fast algorithm
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Strengths
Can easily see what the important structures are and the relationships between them
Can let you ignore “noise” in data Animated transitions Responsive UI
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Weaknesses
Starting view only uses part of the sphere
Moving across the tree can disorient you; cost of clicking on the wrong place is high
Labels not present if node too far from center