An example of a 4 level physical tree with embedded volumes and
the corresponding geometrical configuration are shown in fig 
.
Figure: Example of geometrical tree structure
where A and B are BOXes, C a TRAPezoid, and D and E TUBEs (see [GEOM050] for more detail). Notice that the same physical configuration could be described as well though a 3 level tree if D were defined as a hollow TUBE, with inner radius non-zero and E directly positioned into B. The package accepts a maximum of 15 levels, which should be enough to represent the fine details of a complex structure.