If levels of the graph contain many nodes, it is sometimes
necessary to increase the radius of the circular level to provide
enough space on the circumference of the circle for all the nodes.
It can result in a considerable distance from the previous level.
To avoid it, there is an alternating radial
mode. Alternating radial mode places the nodes of a level alternating
between two circles instead of one circle, resulting in better use
of the space of the layout.
Alternating radial mode uses two circles only when necessary.
For many small and light trees, there is no difference from normal
radial mode. Alternating radial mode affects only large graphs with
many child nodes.
To set alternating radial layout mode:
Call the method:
treeLayout.setLayoutMode(ibm_ilog.graphlayout.tree.TreeLayout.ALTERNATING_RADIAL);

Radial layout mode (right) and alternating radial
layout mode (left)