In radial drawings of hierarchical graphs the vertices are drawn on concentric circles instead of on horizontal lines as in the standard Sugiyama framework. This drawing style is well suited for the visualisation 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 approx. 30% on average.
This paper is the last step to complete the framework for drawing hierarchical graphs in a radial fashion. We present three heuristics for crossing reduction in radial level drawings of hierarchical graphs, and also briefly cover extensions of the level assignment step to take advantage of the increasing perimeter of the circles.