  We present experimental results and a user study for hierarchical drawings of
graphs. A detailed hierarchical graph drawing technique that is based on the
Path Based Framework (PBF) is presented. Extensive edge bundling is applied to
draw all edges of the graph and the height of the drawing is minimized using
compaction. The drawings produced by this framework are compared to drawings
produced by the well known Sugiyama framework in terms of area, number of
bends, number of crossings, and execution time. The new algorithm runs very
fast and produces drawings that are readable and efficient. Since there are
advantages (and disadvantages) to both frameworks, we performed a user study
and the results show that the drawings produced by the new framework are well
received in terms of clarity, readability, and usability. Hence, the new
technique offers an interesting alternative to drawing hierarchical graphs, and
is especially useful in applications where user defined paths are important and
need to be highlighted.
