The hierarchy, in FreeSpace modding, is the method by which FreeSpace determines which pieces of geometry should be used for a given purpose ingame. All geometry, including not only the main hull but also all a models LoDs, debris, turrets etc. are stored by FreeSpace within a single Pof file. Only by separating this geometry hierarchically can the specific function of a particular chunk of geometry be defined. Setting the correct hierarchy for a model can be complex, and as such it often means that many mods reach a bottleneck at the conversions stage.
Hierarchy in Truespace
Although Hierarchy can be set through any conversion method (such as through Collada DAE or the 3DS Max plugin), it was originally only possible through Truespace. Truespace uses local lights as hierarchical branch terminators, as described in the image below.
An example of a completed hierarchy in the Trueview plugin is presented below. For more detail in applying hierarchy to models in Truespace, see Rampage's Post Modding Guide.