A brief history of sunburst visualization

Sunburst maps (also known as treepies) are a relatively new method of visualizing tree structures that is often positioned as an alternative to treemaps.

The very first mentions of sunburst maps can be tracked down to 90s, when various researches experimented with nested pie charts or radial versions of treemaps.

In a few years software developers have adopted the technique for visualizing disk content. Max Howell’s Filelight and Steffen Gerlach’s Scanner are probably the best known examples of such applications.

While working on DaisyDisk we’ve made a series of tweaks to make sunburst maps more suitable for disk visualization:

• all sectors are sorted by size, so visual comparison of folders within the same level can be done in a blink of an eye
• large files clearly catch the eye
• relatively small files and folders within the same level are consolidated into a special “smaller objects” sector making it easier to estimate the amount of disk space taken by large groups of small files (like image collections)
• all children of the same folder have similar colors; such coloring greatly facilitates navigation
• the map is not limited by just 5 levels of depth, outer rings have relatively small thickness, but allow you to reveal space wasters deep inside the disk structure
• the “blossom” animations are not just “eye candy”, but illustrate visual relationships between folders