On the minecraft wiki entry for monster spawners, there is this statement:
A monster spawner is only active when a player is within a distance of 16 blocks from the spawner (where distance is calculated the standard (euclidean) way)
Does this calculation take into account vertical distance as well as horizontal distance?
3 Answers
To test this, I built a tower over some spawners and stayed directly over them about 15-20 blocks higher than they are.
As you can see, the flames have disappeared (and the spawners quit spinning, but you can't tell that from a picture), indicating that they are no longer spawning, despite me being directly over them.
So yes, it does take into account vertical distance.
2Yes it does take into account vertical and horizontal distance. If you are 6 blocks across and 10 blocks down from the spawner then it will continue to spawn mobs.
The except to this is if the spawner has spawned 4 mobs. After spawning 4 mobs it will wait from 10 to 40 seconds then rechecks an area 17x17x9 to see if there is less than 6 mobs of the monster spawner's type. If so, it will spawn more.
In short, monster spawners only work if a player is standing near it.
source: Minepedia - Monster Spawner
1It also seems, that the 16 block sphere that the distance is counted in, emenates from the center of the top surface of the block the player is standing on.
