A radial adaptation of the Sugiyama framework for visualizing hierarchical information

In radial drawings of hierarchical graphs, the vertices are placed on concentric circles rather than on horizontal lines and the edges are drawn as outward monotone segments of spirals rather than straight lines as it is done in the standard Sugiyama framework. This drawing style is well suited for the visualization of centrality in social networks and similar concepts. Radial drawings also allow a more flexible edge routing than horizontal drawings, as edges can be routed around the center in two directions. In experimental results, this reduces the number of crossings by approximately 30 percent on average. Few crossings are one of the major criteria for human readability. This paper is a detailed description of a complete framework for visualizing hierarchical information in a new radial fashion. Particularly, we briefly cover extensions of the level assignment step to benefit from the increasing perimeters of the circles, present three heuristics for crossing reduction in radial level drawings, and also show how to visualize the results.