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Cone Trees and Collapsible Cylindrical Trees

Cone Trees and Collapsible Cylindrical Trees

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Cone Trees and Collapsible Cylindrical Trees

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  1. Cone Trees andCollapsible Cylindrical Trees Joshua Foster February 19, 2003

  2. Papers • Cone Trees: Animated 3D Visualizations of Hierarchical Information • Collapsible Cylindrical Trees: A Fast Hierarchical Navigation Technique

  3. Goals of Cone Trees • 3D visualization (display more information in same screen space) • Interactive animation (shifts some of the cognitive load to human visual perception system)

  4. 2D Aspect Ratio • Most real-life hierarchies tend to be broad, shallow, and unbalanced • 2D graph-building algorithms lay out a tree based on 2 parameters: • b – number of children per node (branching factor) • l – number of levels • Aspect ratio =

  5. Examples b = 2, l = 5, aspect ratio = 3.2 b = 3, l = 4, aspect ratio = 6.75

  6. Aspect Ratio vs. Number of Levels

  7. Aspect Ratio (cont’d) • Cone Tree aspect ratio is fixed at 4:3 (1.25) • Cone diameter and level height adjusted to accommodate • Side effect: Number of levels limited to 10

  8. User Perceptions • “Fisheye” view – selected objects are brighter, closer, and larger • Shadows provide depth information • Animation provides information about relationships

  9. User Interaction: Gardening • Gardening consists of two operations: • Pruning allows unwanted sublevels to be “cut” from the tree • Growing adds sublevels back in • Additional operations: • Prune Others: remove all the siblings of a selected node

  10. User Interaction (cont’d) • Changing Tree Structure: • User may drag a node (and its entire substructure) to a new place on the tree • Searching: • User may search nodes for text or properties • Search produces a relevancy bar at each node

  11. Applications • File browser • Organizational structure of a company • Company operating plan • Cone tree manipulation used to ‘restructure’ projects

  12. Problems? • Fixed aspect ratio imposes limits on tree size • Limits are roughly 1000 nodes, 10 levels, and maximum branching factor of 30 • Animation is more effective for unbalanced trees

  13. Papers • Cone Trees: Animated 3D Visualizations of Hierarchical Information • Collapsible Cylindrical Trees: A Fast Hierarchical Navigation Technique

  14. Goals of Collapsed Cylindrical Trees (CCT) • What they don’t do: • Visualize the entire tree structure • Provide insight into complex hierarchies • What they do do: • Allow quick navigation through hierarchies, find and perform an action on a specific node

  15. Motivation • Problems: • Simple GUI operations such as selecting menu items require long vertical mouse movements • Screen space may be limited (ex: cellphone displays) • Solution: • Map list items onto a rotating cylinder

  16. CCT Approach • Developed for webpage navigation • Individual nodes are important, not the entire tree • Tree navigation with other techniques: • Tree maps, cone trees, etc: too cluttered, hard to find individual node • Hyperbolic trees: node positions constantly changing, hard to build up “muscle memory”

  17. Example: Sitemap Navigation

  18. Layout • Every parent node is a cylinder, with the facets listing its child nodes • Children of the root node are shown in parallel • Child cylinders are nested • Endless cylinder concept

  19. User Interaction • Any node can be reached with a series of short mouse movements • Vertical mouse movements over a cylinder cause rotation • Mousing over a facet causes the child cylinder to appear

  20. Building “Muscle Memory” • Facets are always the same size • The selected cylinder is always the same width • Therefore, mouse movements are quickly memorized and become automatic

  21. Size Limitations • No more than 7 top-level nodes • Branching factor unlimited (due to endless cylinder concept) • Maximum number of nodes: • numrc * numfd = 7 * 206 = 4.48x108

  22. Applications • WWW sitemap navigation • Table of contents for Internet radio guides, manuals, tutorials, etc.

  23. User Perceptions • Fun to use • Comprehensible to persons with no 3D / visualization experience • Balanced: • More information than with traditional menus • Less information than with cone trees, treemaps, etc.

  24. Virtual Reality Markup Language (VRML) • Allows specification of 3D scenes through which the user can navigate • One .VRML file contains each object description • User can navigate through the scene: • “Walk” (6 degrees of freedom) • “Seek” (click an object and move closer toward it) • “Examine” (rotate or zoom the whole scene)

  25. Implementation • XML tree representation • Use Java to convert XML to VRML files and Javascript

  26. Performance • Acceptable frame rate with 300-node tree on a 750 MHz PC with mid-range video card • At most numrc + d - 1 cylinders shown at once

  27. Possible Enhancements • To increase number of root children: • Matrix-style layout • Toroidal cylinder arrangement

  28. Questions?