Interacting with Huge Hierarchies: Beyond Cone Trees Jeromy Carriere, Rick Kazman Computer Graphics Lab, Department of Computer Science University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 System Lab 高君豪

Introduction This paper describes a system called fsviz which visualizes arbitrarily large hierarchies while retaining user control. –based on cone tree usage-based filtering animated zooming hand-coupled rotation fish-eye zooming coalescing of distant nodes texturing effective use of colour for depth cueing the applications of dynamic queries

Presentation They improve on the layout algorithms for cone trees. –Remove all visual clutter –making better use of colour and node shape –providing fish-eye viewing

Colour In the implementation presented here, colour conveys file size. –The greater the saturation of the colour, the larger the file. They scheme maps ranges of file sizes to colours distribution is given to size ranges containing an equal number of files.

Shape Form initial prototyping with fsviz, we have observed that users can easily pick out files of different types when the nodes representing those files are different shapes. It should be noted that in the printed representation of the visulaization, it is difficult to distinguish node shapes.

Text This information is conveyed via text placed near the nodes in the tree. The text scales and rotates along with the tree such that it always faces the viewer.

Animation The hand-coupled rotation, in which the user can directly manipulate both their view of the cone tree structure and the orientation of the cone tree’s subcomponents. The software provides automatic animation in two ways. –The user can select a set of nodes in the tree and fsviz will perform sequence of “zooms” to bring the user directly to that set. –When a file is selected using the file information browser, the node representing that file will be rotated to the front of the tree.

Tree Layout A simple algorithm maydetermine the radii of the sub-cones within the tree based solely on the parent node in the tree. –R(h) represents the radius of a tree at height h –R i is some fixed initial radius –small trees

Tree Layout It can effectively allocate space around the radii of the cones in the tree to accommodate the children. –all overlap between subtrees can be eliminated At all levels above, the circumference for a cone at level n-1 is estimated by: –where r i,n is the radius of the child i ate level n

Tree Layout The radius is then calculated with: The arc length required for a child will be estimated by: Subtrees are placed around the cone, with angles defined by:

Fish-eye Viewing The basic mechanism depends on a Degree of Interest (DOI) function which defines the “importance” of a particular node in the structure. –where x is the node being considered, y is the current focus, and root is the root node

Automatic Subtree Coalescing The technique was applied in fsviz to reduce the number of nodes displayed at a given time. –A subtree is sufficiently distant from the user’s focus node so as to be practically of no interest to them. the subtree is collapsed the subtree is coalesced This representation is currently a tetrahedron, whose colour reflects the size of the directory itself.

Automatic Subtree Coalescing This technique serves two purposes: –it produces an improvement in rendering efficiency –visual clutter is reduced