These images are part of a paper titled "Smoother transitions between breadth-first-spanning-tree-based drawings" and part of the Proceedings of Graph Drawing, 14th International Symposium, GD 2006, Karlsruhe, Germany, September 18-20, 2006.In this paper the authors propose an alternative view of the tree radial layout where nodes are drawn as "ballons" where each child node is positioned on the centrifugal semi-circle of the ballon that lies outside its parent. No thick edges need to be drawn in the case where edges and nodes are denoted by the overlapping ballons.
