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Monster Spawner

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Monster Spawner
Monster Spawner.gif
Monster Spawner
Type

Solid Block

Requirements

None

Physics

No

Transparency

Graphical Only

Luminance

No (Small amount of light for Pocket Edition)

Blast resistance

25

Hardness

5

Tool

A wooden pickaxe or better is required to mine this block

Renewable

No

Stackable

Yes (64)

Flammable

No

Experience

Mined: 15–43

First appearance

Infdev Seecret Friday 2

Tile Entity ID

MobSpawner

Data value

dec: 52 hex: 34 bin: 110100

Name

mob_spawner

Monster spawners are blocks that can spawn mobs.

Obtaining[edit]

Spawners can not be obtained at all in survival mode. The proper tool to mine them with is the pickaxe.

Block Hardness Tool Breaking time (seconds)
Hand Wooden Stone Iron Diamond Golden Shears Sword

Monster Spawner
5
25 3.75 1.875 1.25 0.9375 0.625

It is also not in Creative mode inventory (except in Pocket Edition) and as such must be obtained with commands.

Natural generation[edit]

A monster spawner that spawns skeletons.

Spawners can generate naturally in these places, spawning mobs chosen randomly when generated:

Dungeons
Spawns zombies (50% chance), skeletons (25%), or spiders (25%).
Abandoned mine shafts
Spawns Cave Spiders. Located in horizontal tunnels, heavily surrounded by cobwebs.
In Pocket Edition it spawns regular spiders instead.
Strongholds
Spawns silverfish. Located in the End Portal room. One per stronghold.
Nether Fortresses
Spawns Blazes. Located on Nether fortress balconies with stairs leading up to them.

Behavior[edit]

A spawner will spawn mobs in the surrounding area, provided suitable spawning locations for the block's mob type can be found in the area. Spawner blocks can spawn some mobs in mid-air, ignoring general rules about spawning on solid ground. The spawned mob can be changed by using a spawn egg on the spawner.

A monster spawner is only active when a player is within a radius of 16 blocks from the spawner. While the block is active, it will spawn mobs within an 8×2×8 block volume (8 wide and 2 high and 8 long) centered on the center of the block, effectively meaning mobs can spawn in a 9x9 area, or 3.5 blocks from the spawner. Mobs can spawn anywhere in this range that is suitable, even if the immediate vicinity of the spawner block itself is not suitable. The horizontal distribution is triangular, with positions near the spawner more likely than ones 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 the 8 × 8 range, but vertically, mobs will spawn with their legs at either the same layer as the spawner block, one block above it, or one block below it. Due to the y-coordinate ranging from -1 to 1 of the bottom surface of the spawner block, there are 3 vertical blocks of space in which mobs can spawn even though the spawning volume is only two blocks in height. This 3-block vertical space can be proven to exist with cave spider spawners and glass to limit the spawning space.

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 opaque blocks to conform with the mobs' height, width, or other rules governing their individual spawn volumes. 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 that must contain only air.

Summary of maximum spawn volumes for common monster spawners
Mob type Required Volume Failure rate from 8×8×4 volume[note 1] Vertical
alignment

Pig
8.9 × 8.9 × 2.9 2.531252%




Cave Spider
8.7 × 8.7 × 2.5 1.531252%




Silverfish
8.3 × 8.3 × 2.7 0.28125%




Zombie


Skeleton


Blaze
8.6 x 8.6 x 3.8 1.125%





Spider
9.4 × 9.4 × 2.9 6.125%



  1. 8×8×3 is the actual volume across which spawners spawn entities, but this volume only contains the entity's center. The failure rate assumes 8×8×4 because it is a popular misconception that 8×8×4 is the maximum efficiency volume of empty space for mob spawners - it actually depends on the size of the entities themselves. Note that 10x10x4 is guaranteed to accommodate all of the above mobs. Also note that this failure rate only accounts for failures due to attempting to spawn a mob at the edges of the spawn range, not other causes of failure such as mobs attempting to spawn intersecting the spawner block itself.

For all of the volumes listed in the table, the horizontal plane is centered on the center of the spawner block. While the spawning volume for pigs is 8.9×8.9×2.9, the requirement of grass blocks that are necessary for pigs to spawn will reduce the actual volume in which they successfully spawn.

The block will attempt to spawn 4 mobs at randomly chosen points within the spawning area, then wait anywhere from 200 to 799 ticks (10 to 39.95 seconds) before spawning again. As it waits, the mob inside the block will spin faster and faster. Except for spawning on a solid block, all of the usual requirements for spawning must be met (not in a solid block, correct light level, etc.), so the spawner will often produce fewer than 4 mobs. When it does spawn, it will "poof", and more lightless flames will temporarily appear around the Spawn block. If the block fails to spawn any mobs because it did not pick any suitable locations, it will repeat this process every tick until it succeeds. Only when it manages to spawn at least one mob will it start waiting for the next cycle. If, at the time of spawning, 6 or more mobs of the block's type are present within a 9×9×9 area, centered on the spawner block, the spawner "poofs" without creating any mobs and then waits for the next cycle.

In Peaceful difficulty, monster spawner blocks will still appear and work, but any spawned hostile mobs will disappear the instant they spawn. Zombie Pigmen, Magma Cubes, and Ghasts will not spawn at all.

An interesting quirk of monster spawners (and end portal frames and slime blocks) is that they are transparent in their rendering only - unlike all other transparent blocks, they can have torches and redstone placed on them, conduct a redstone current, will suffocate mobs, and more.

Detailed spawning algorithm[edit]

This pseudo-code is derived from the de-compiled source of 1.7.10

if (there is a player within the range of activatingRangeFromPlayer) 
{
    if (spawner delay == -1) 
    {
        reset spawner delay
    }

    if (spawner delay > 0) 
    {
        decrement spawner delay by 1
        cancel this spawn
    }

    loop for the number of entities we should spawn 
    {
        if (the number of entityTypeName in a 2*spawnRange+1 centered cube > maxNearbyEntities) {
            reset spawner delay
            exit loop
        }

        X = Spawner.x + random(spawnRange*2)-spawnRange;
        Y = Spawner.y + random(3)-1;
        Z = Spawner.z + random(spawnRange*2)-spawnRange;

        if (entity can spawn at (X,Y,Z)) 
        {
            Spawn entityTypeName at (X,Y,Z)
            Play Sound Effect
            Spawn Particles
        }
    }

    if (at least one entity was spawned) 
    {
        reset spawner delay
    }
}

Default values:
    activatingRangeFromPlayer = 16
    spawner delay = 20
    maxNearbyEntities = 6
    spawn range = 4
    entityTypeName = Pig

Outcomes (default):
    A player must be within a 16 block centered sphere
    There must not be more than 6 pigs within a 9x9x9 centered cube
    The pig must be able to spawn at the chosen location (must not be inside a block, meet lighting conditions etc.)
    If all mobs fail to spawn, it will try again on the very next tick.

Custom spawners[edit]

Monster spawners are capable of much more than they are used for in survival Minecraft. Using commands, they can be customized in many ways:

  • They can be made to spawn any kind of entity.
  • A single spawner can spawn multiple different entities, chosen at random from a list.
  • Properties can be set on the spawned entities.
  • Various range and timing properties of the spawner can be altered.

Detailed technical information about custom spawners can be found in the chunk format reference.

Video[edit]

History[edit]

Infdev
Seecret Friday 2 Added mob spawners. They could be picked up and when placed, spawned pigs.
June 27, 2010 Mob spawners given a unique ID, reducing crashes.
Beta
Changed name from mob spawner to monster spawner.
1.2 Monster spawners again now show a rotating model inside of what they spawn in single player after being missing for several versions.
Official release
1.0.0 Beta 1.9-pre1 Changed monster spawner texture to a darker color.
Beta 1.9-pre5 Squid spawners now only work in a narrow elevation range, from 46 to 62.
Monster Spawners no longer drop after destroyed. Before this update, it was possible to obtain a monster spawner using a tool enchanted with Silk Touch.
Monster spawners are now easier to destroy.
1.2.1 12w06a Monster spawners now show the mob they are spawning in multiplayer; previously it always showed a pig.
1.3.1 12w22a Monster spawners will now drop experience when destroyed.
12w26a Monster spawners now support extra data pertaining to what they spawn.
1.8 14w26c The horizontal spawning range is now calculated from the center of the block rather than the northwest corner.
The exclusion zone has been reduced: for a default spawner, the 6 mobs must be in a 9×9×9 region rather than 17×9×17 to prevent spawning.
14w28b The type of mob spawner can be changed by using a spawn egg on it.
Pocket Edition Alpha
0.9.0 build 1 Added monster spawners.
build 2 Added monster spawners to the creative inventory. The type of mob spawner can be changed using a spawn egg.
build 9 Monster spawners now emit light.
Console Edition
TU1 Added monster spawners.

Issues[edit]

Issues relating to "Monster Spawner" are maintained on the issue tracker. Report issues there.

Trivia[edit]

  • Unlike most other solid blocks, the monster spawner supports texture with transparent areas, without showing what's behind.
  • When mining near a monster spawner that has no valid places to spawn, sometimes a monster will spawn immediately after a block is mined. It's speculated this might happen because the spawner gets a chance to spawn before the lighting calculation for the space the block occupied.
  • If a spawner is made to spawn a Giant, Ghast, or Iron Golem; the mob inside will be larger than the spawner and will appear to physically extend beyond the confines of the spawner block's sides.
  • The miniature mob inside the monster spawner is an actual mob of that type. Thus, if a spawner is configured to spawn Ender Dragons or Withers, their boss health bar is visible while looking at the spawner.

Gallery[edit]

See also[edit]

References[edit]