The level layout mode partitions the node into levels
and arranges the levels horizontally or vertically. The root is placed
at level 0, its child nodes at level 1, the child nodes of those child
nodes at level 2, and so on. In contrast to the free layout mode,
in level layout mode the nodes of the same level are justified with
each other even if they are not siblings (that is, they do not have
the same parent).
To set the level layout mode:
Call the method:
treeLayout.setLayoutMode(ibm_ilog.graphlayout.tree.TreeLayout.LEVEL);
The following figure shows the same graph in free layout
mode and in level layout mode.

Free layout mode and level layout mode