Monster Spawner

A monster spawner is a type of spawner found in a variety of structures. It constantly summons instances of the mob displayed within it as long as a player is in range and the light levels are correct for that mob type to spawn nearby. It only drops experience orbs when broken, and cannot be moved from where it is found.

Obtaining

Monster spawners cannot be obtained in Survival, even with Silk Touch. A monster spawner can be obtained in Creative mode by taking it from Creative inventory, by using the command, or by using . It is initially empty and inert, but can be configured to spawn a desired mob by a spawn egg on the placed block. A , or command can also be used to obtain a monster spawner.

Breaking

If broken with a pickaxe, a monster spawner drops 15-43 experience. When mined with anything else, it drops nothing.

Natural generation

Monster spawners can generate naturally in the following places:

One in the center of the monster room spawning one of the following mobs with the indicated frequency: zombie (50%), skeleton (25%), or spider (25%).

Any number of cave spider monster spawners, densely surrounded by cobwebs, scattered throughout.

Usage

A monster spawner spawns mobs in an (at most) 9×3×9 volume (see ) around it when the player is within 16 blocks. Suitable spawning locations for the block's mob type are provided in or around the spawning volume. The monster spawner attempts to spawn four mobs around it, then waits from 10 to 39.95 seconds before attempting to spawn more. In Peaceful difficulty, monster spawners still activate but do not spawn monsters, including zombie horses and camel husks . Monster spawners are transparent, but they behave like leaves in that they diffuse sky light coming from directly above.

Mechanics

A monster spawner activates when a player (that's not in Spectator mode) comes within a spherical radius of 16 blocks from the center point of the block; i.e. 15.5 blocks from the monster spawner itself. The player's presence is determined by coordinates at their foot level, meaning that a player standing exactly 15.5 blocks below the spawner doesn't activate it, even though their head is in range. an active monster spawner attempts to spawn mobs within a 4-block horizontal and 1-block vertical range; that is, in a 9×3×9 volume centered on the monster spawner. , the horizontal spawning range is 4 blocks taxicab distance, creating spawning volume extending 4 blocks in each cardinal horizontal direction from the sides of the monster spawner; its horizontal cross-section is therefore diamond-shaped. Mobs can spawn anywhere in this range that is suitable, with mobs more likely to spawn closer to the monster spawner than farther away. While mobs are spawned at fractional x and z-coordinates (i.e. not aligned to blocks), they are spawned at an integer y-coordinate. Horizontally, a mob can spawn with its center point anywhere within range, but vertically, mobs spawn with their legs at either the same layer as the monster spawner block, one block above it, or one block below it. (Note that when there are other blocks slightly intersecting the mob's hitbox, they can sometimes glitch further away - often up - but this does not make it a true spawning point.) A monster spawner attempts to spawn 4 mobs at randomly chosen points within the spawning volume, then waits anywhere from 200 to 799 ticks (10 to 39.95 seconds) before spawning again. As it waits, the mob model inside the block spins faster and faster. Except for the normal solid-block spawning requirement, all the remaining ones must be met (not in a solid block, correct light level, etc.), so the monster spawner often produces fewer than 4 mobs. When it does spawn, more flame particles temporarily appear around it, and puffs of smoke are emitted from the spawned mobs or the northwest corner of the spawner . If the monster spawner fails to spawn any mobs because it did not pick any suitable locations, it repeats this process every tick until it succeeds. It starts the next wait cycle only after successfully spawning at least one mob. If 6 or more mobs of a monster spawner's type have their hitbox intersecting a 9×9×9 volume centered on the monster spawner block or a 16×10×16 volume centered on the lower northwest corner of the monster spawner block , the monster spawner "poofs" without creating any mobs and then waits for the next cycle. This is checked before each of the four spawn attempts.

Spawning requirements

A monster spawner performs a relaxed version of the ordinary spawning check: the general solid block requirement is removed, but the volume (hitbox of the mob) is kept along with some other checks according to mob specifics. As a result, for some types of mobs to spawn in the outer planes of the spawning volume, some planes outside the volume may also need to be free of solid blocks to conform with the mobs' height, width, or other rules governing their individual spawn volumes. Examples: For mobs that are two or more blocks tall such as zombies, skeletons, or blazes to spawn in the top y-layer, the layer above must contain only a transparent block such as air, glass, leaves, etc. , a turtle monster spawner can spawn turtles only on sand blocks less than 4 blocks above sea level (typically at Y=62). no biome/light/height conditions apply for turtles in monster spawners. , some animals require light level ≥7, e.g. chicken, sheep, cow, rabbit. Others ignore the light level condition given in the spawning rules json files, e.g. parrot, turtle. This suggests that some of the early animals have hard-coded requirements when used in monster spawners.

For all of the volumes listed in the table, the horizontal plane is centered on the center of the monster spawner. While the spawning volume for pigs is 8.9×2.9×8.9, the requirement of grass blocks that are necessary for pigs to spawn reduces the actual volume in which they successfully spawn to 8.9×1.0×8.9. Other mobs can spawn in mid-air, ignoring general rules about spawning on solid ground. The spawn conditions do not include biomes for most mobs. As such, monster spawners can place mobs where they normally wouldn't generate. For example, a mooshroom monster spawner can operate in a plains biome as long as there are mycelium blocks within the spawn area because the mooshroom's spawning code checks only for mycelium. The reason mooshrooms are not actually spawned elsewhere is that the game does not normally try to spawn them in other biomes: only the mushroom field biome has mooshroom on the list of things to spawn.