EVENT_RESETGOTPICS is a Misc Event.
This event is triggered before mirrors are drawn, directly after the mirror's EVENT_DISPLAYROOMS call. Hence, this event executes at framerate, rather than ticrate.
It is also triggered one final time during the transition when the mirrors are out of view and not being rendered anymore.
The purpose of this event is to allow mods to reset entries in the gotpic array to 0. An entry in the gotpic array is 1 if the tile in question has been observed onscreen by the player.
This is primarily useful for skyboxes, which are rendered in place of the null tile (HOM effect under normal circumstances). This can be set up such that if gotpic for the skybox tilenum is 0, the skybox view is no longer displayed, thus improving performance.