Changing the mapping of a plateau's area from number of files to the total size of files within it results in the graphical representation of disk usage shown in Figure 6 . In this view of the tex directory, three subdirectories containing large, uncompressed PostScript files and large, uncompressed TIFF images stand out from the rest. Another example of an Information Pyramids visualisation is shown in Figure 7 . Here Sun's Java JDK 1.0.2 distribution tree is shown, in disk usage style. The pyramid at front left is the src subdirectory.
Broad hierarchies result in many pyramids at each tier, but remain manageable.
Decreasing the relative height of successive plateaus decreases the prominence of deeper levels of the hierarchy in the overall landscape, i.e. deeper levels become invisible sooner. The best visual representation is of little use without accompanying navigational facilities. By navigating through the pyramid landscape, users can, for example, focus on a particular part of the hierarchy and can see progressively more detail of that part, or can float above the pyramid landscape for an overview. The current prototype file system visualiser using Information Pyramids is written in Java and uses our in-house GE3D graphics interface to either OpenGL or Mesa libraries for 3d graphics output. In order to maintain interactive frame rates, especially for very large hierarchies, a current focus of work is to implement graceful degradation of the rendering during movement.