The Effective Representation of Large Graphs

1
The Effective Representation of Large Graphs

• D.J. Duke
• Department of Mathematical Sciences
• University of Bath

2
Graph Visualization

• applications include
• social structures
• biochemical pathways
• web access patterns
• visualization tools
• typically lt 104 nodes
• limited control of filtering and interaction

3
Royere

• modular graph visualization tool
• developed at CWI Amsterdam
• modules from Bath and LaBRI
• www.cwi.nl/InfoVisu/
• components provide
• layout tree, DAG, force-directed, ring
• metrics highlight structural properties
• clustering metric/neighbourhood
• interaction pan/zoom/fisheye etc.

4
Metrics

• significance
• based on
• structural properties
• application weights
• Strahler metric
• S(v) max S(ki) C
• C (p ? 1), if S(ki) S(kj)
• C (p ? 2), otherwise
• Other metrics, e.g. Fission (Marshall, 2001)

5
Skeletons

• metric determines degree of interest
• elide nodes with DOI below threshold
• but provide an overview of unexplored regions.

6
Ongoing work in graph viz.

• visualization techniques
• interaction between clustering and layout
• efficient algorithms
• generalized skeletons
• human aspects
• role of task and domain knowledge
• interaction
• cognitive demands

7
Cognitive foundations
8
Non-photorealistic rendering

• traditional rendering in CG
• aim for level of photo realism
• simulate light-material interaction
• recent growth in NPR
• enhance perception of detail
• artistic techniques
• sketching, shading, painting
• image or object-space techniques

9
NPR in visualization

• motivations
• characterise structure of surfaces
• differentiate regions (through texture)
• represent higher-dimensional data, e.g. tensors
• capture impression of motion in flow
• challenges
• real-time interactive rendering
• dealing with abstraction / simplification

10
The value of sketchiness
Schumann, Strothotte, Raab Laser Assessing the
affect of non-photorealistic rendered images in
CAD. In Proc. CHI96, ACM Press
11
NPR and graph visualization