View source for PM file

The [[PM file]] format is an obsolete [[Mesh file]] format supported by [[Auran Jet]]. It provided support for an unusual form of [[LOD]] that was designed for high efficiency and flexibility on the early GPU hardware in existence at the time of development. Meshes could scale over a wide range of polygon counts by following a simple pre-defined triangle splitting/merging sequence. Unfortunately it never entirely lived up to its promise of automatic LOD generation or fully scalable scene detail, offering worse visual quality than hand-created LODs.

In the subsequent period, the format suffered a number of additional blows:
* Hardware optimisation requirements changed such that the Progressive Mesh technique was no longer particularly optimal.
* 3D modelling tools began to offer high-quality automatic LOD mesh generation which exceeded the capabilities of the PM file format.
* Users began to demand a consistent visual quality which was beyond that offered by the Progressive Mesh technique.

Full support for PM files within Trainz was dropped in favour of the [[LM.txt file]] technique. Trainz now ignores the progressive mesh data, and simply loads PM files as if they were a standard [[IM file]] with a single (maximum) level of detail.