path_corner is used by both monsters and func_train entities. The additional features in Quoth affect each differently, so they are discussed in turn
Set “duration” on a path_corner and any func_train which visits this corner will inherit the value of “duration” set. This means it will take “duration” seconds to travel between path_corners from that point onwards. By having each path_corner set duration, you can control the lengths of each stage of the train’s journey.
Similarly if duration is not set, then the “speed” key on a path_corner will update the func_train’s “speed” when it reaches the corner.
The train will use the duration or speed it is given initially for it’s first journey between path corners, it will not inherit the duration of it’s starting target.
The “event” key can be used to trigger an event when a func_train leaves this corner. Set “event” to the targetname which you wish to trigger. This doesn’t trigger if the train arrives and stops with a “wait”.
Set “wait” to “-1” and a train which reaches this corner will stop. The stopped train will resume moving when next triggered.
Quoth added support for additional features on the path_corner for monsters. Unfortunately the additional features also changed the way that regular path_corners are treated, in a way that broke some ID1 maps. In particular, the new features required monsters to stand on top of the path corner, rather than just touch it, which was impossible when path_corners were placed very close to or touching walls.
Quoth 2.2 attempts to fix the broken maps while keeping Quoth maps functional, but path_corner has complicated behaviour as a result. We recommend that mappers use one of the following two entities for monster patrols in new maps:
path_corner_contact behaves exactly like path_corner does in ID1 quake, monsters head to the next path corner as soon as they make contact with their current target. No waiting, no angles.
path_corner_precise supports all the Quoth features like “wait” and “angles” (see article for details), and monsters have to line up with the path_corner precisely before going for the next one.
path_corner attempts to switch between these two models automatically to maintain compatibility with existing maps. Initially path_corners behave like path_corner_contact for compatibility with ID1 maps. As soon as a monster navigates towards a path_corner which has a “wait” value, all path_corner entities in the map switch to path_corner_precise mode to support the Quoth features.