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f748588
spawn placements
IchHabeHunger54 Jul 28, 2026
87a9085
address ChampionAsh's comments
IchHabeHunger54 Jul 28, 2026
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67 changes: 67 additions & 0 deletions docs/entities/livingentity.md
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Original file line number Diff line number Diff line change
Expand Up @@ -221,6 +221,73 @@ DeferredItem<SpawnEggItem> MY_ENTITY_SPAWN_EGG = ITEMS.registerItem("my_entity_s

As an item like any other, the item should be added to a [creative tab][creative], and a [client item][clientitem], [model] and [translation] should be added.

### Spawn Placements

By default, spawning will be possible anywhere, including inside blocks and in midair. To prevent this, a spawn placement must be registered. This happens in the `RegisterSpawnPlacementsEvent` like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// SpawnPlacementType is a functional interface that checks whether a given position is valid
// for spawning. You can add your own SpawnPlacementType if needed,
// see the implementation of SpawnPlacementTypes for reference.
// Vanilla values include NO_RESTRICTIONS, IN_WATER, IN_LAVA and ON_GROUND.
SpawnPlacementTypes.ON_GROUND,
// The heightmap type to use. This provides the initial height to check during world generation,
// later this is ignored and just uses the world surface. Possible values are

@ChampionAsh5357 ChampionAsh5357 Jul 29, 2026

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You can get rid of the latter half of this sentence. Saying it's only used during worldgen is good enough.

// WORLD_SURFACE, OCEAN_FLOOR, MOTION_BLOCKING and MOTION_BLOCKING_NO_LEAVES.
Heightmap.Types.WORLD_SURFACE,
// A predicate to check additional spawn rules, e.g. light. Can either be specified here
// as a lambda, or (more commonly) as a static method in the entity class.
(entityType, level, spawnReason, pos, random) -> {
// Make our mob only spawn on grass blocks.
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// For our own mobs, any operation may be used.
RegisterSpawnPlacementsEvent.Operation.OR
);
}
```

It is also possible to modify vanilla's or other mods' spawn placements. You can use one of `Operation.AND` (for extra spawn restrictions), `Operation.OR` (for alternate spawn mechanisms) or `Operation.REPLACE` (to completely replace the spawn placement, use a [low-priority event listener][priority] in this case) like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// When not using Operation.REPLACE, leave the spawn placement type
// and the heightmap type at null.
null,
null,
Comment thread
IchHabeHunger54 marked this conversation as resolved.
// Like above, check the additional/alternate spawn rules.
(entityType, level, spawnReason, pos, random) -> {
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// Use the appropriate Operation here.
RegisterSpawnPlacementsEvent.Operation.AND
);
}
```

The event also provides two utility overloads (where `spawnPredicate` is the lambda we used earlier):

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, Operation.OR)
event.register(MY_ENTITY.get(), spawnPredicate);
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, operation)
event.register(MY_ENTITY.get(), spawnPredicate, operation);
}
```

### Natural Spawning

_See also [Entities/`MobCategory`][mobcategory], [Worldgen/Biome Modifers/Add Spawns][addspawns], [Worldgen/Biome Modifers/Add Spawn Costs][addspawncosts]; and [Spawn Cycle][spawncycle] on the [Minecraft Wiki][mcwiki]._
Expand Down
67 changes: 67 additions & 0 deletions versioned_docs/version-1.21.10/entities/livingentity.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -221,6 +221,73 @@ DeferredItem<SpawnEggItem> MY_ENTITY_SPAWN_EGG = ITEMS.registerItem("my_entity_s

As an item like any other, the item should be added to a [creative tab][creative], and a [client item][clientitem], [model] and [translation] should be added.

### Spawn Placements

By default, spawning will be possible anywhere, including inside blocks and in midair. To prevent this, a spawn placement must be registered. This happens in the `RegisterSpawnPlacementsEvent` like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// SpawnPlacementType is a functional interface that checks whether a given position is valid
// for spawning. You can add your own SpawnPlacementType if needed,
// see the implementation of SpawnPlacementTypes for reference.
// Vanilla values include NO_RESTRICTIONS, IN_WATER, IN_LAVA and ON_GROUND.
SpawnPlacementTypes.ON_GROUND,
// The heightmap type to use. This provides the initial height to check during world generation,
// later this is ignored and just uses the world surface. Possible values are
// WORLD_SURFACE, OCEAN_FLOOR, MOTION_BLOCKING and MOTION_BLOCKING_NO_LEAVES.
Heightmap.Types.WORLD_SURFACE,
// A predicate to check additional spawn rules, e.g. light. Can either be specified here
// as a lambda, or (more commonly) as a static method in the entity class.
(entityType, level, spawnReason, pos, random) -> {
// Make our mob only spawn on grass blocks.
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// For our own mobs, any operation may be used.
RegisterSpawnPlacementsEvent.Operation.OR
);
}
```

It is also possible to modify vanilla's or other mods' spawn placements. You can use one of `Operation.AND` (for extra spawn restrictions), `Operation.OR` (for alternate spawn mechanisms) or `Operation.REPLACE` (to completely replace the spawn placement, use a [low-priority event listener][priority] in this case) like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// When not using Operation.REPLACE, leave the spawn placement type
// and the heightmap type at null.
null,
null,
// Like above, check the additional/alternate spawn rules.
(entityType, level, spawnReason, pos, random) -> {
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// Use the appropriate Operation here.
RegisterSpawnPlacementsEvent.Operation.AND
);
}
```

The event also provides two utility overloads (where `spawnPredicate` is the lambda we used earlier):

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, Operation.OR)
event.register(MY_ENTITY.get(), spawnPredicate);
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, operation)
event.register(MY_ENTITY.get(), spawnPredicate, operation);
}
```

### Natural Spawning

_See also [Entities/`MobCategory`][mobcategory], [Worldgen/Biome Modifers/Add Spawns][addspawns], [Worldgen/Biome Modifers/Add Spawn Costs][addspawncosts]; and [Spawn Cycle][spawncycle] on the [Minecraft Wiki][mcwiki]._
Expand Down
67 changes: 67 additions & 0 deletions versioned_docs/version-1.21.11/entities/livingentity.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -221,6 +221,73 @@ DeferredItem<SpawnEggItem> MY_ENTITY_SPAWN_EGG = ITEMS.registerItem("my_entity_s

As an item like any other, the item should be added to a [creative tab][creative], and a [client item][clientitem], [model] and [translation] should be added.

### Spawn Placements

By default, spawning will be possible anywhere, including inside blocks and in midair. To prevent this, a spawn placement must be registered. This happens in the `RegisterSpawnPlacementsEvent` like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// SpawnPlacementType is a functional interface that checks whether a given position is valid
// for spawning. You can add your own SpawnPlacementType if needed,
// see the implementation of SpawnPlacementTypes for reference.
// Vanilla values include NO_RESTRICTIONS, IN_WATER, IN_LAVA and ON_GROUND.
SpawnPlacementTypes.ON_GROUND,
// The heightmap type to use. This provides the initial height to check during world generation,
// later this is ignored and just uses the world surface. Possible values are
// WORLD_SURFACE, OCEAN_FLOOR, MOTION_BLOCKING and MOTION_BLOCKING_NO_LEAVES.
Heightmap.Types.WORLD_SURFACE,
// A predicate to check additional spawn rules, e.g. light. Can either be specified here
// as a lambda, or (more commonly) as a static method in the entity class.
(entityType, level, spawnReason, pos, random) -> {
// Make our mob only spawn on grass blocks.
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// For our own mobs, any operation may be used.
RegisterSpawnPlacementsEvent.Operation.OR
);
}
```

It is also possible to modify vanilla's or other mods' spawn placements. You can use one of `Operation.AND` (for extra spawn restrictions), `Operation.OR` (for alternate spawn mechanisms) or `Operation.REPLACE` (to completely replace the spawn placement, use a [low-priority event listener][priority] in this case) like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// When not using Operation.REPLACE, leave the spawn placement type
// and the heightmap type at null.
null,
null,
// Like above, check the additional/alternate spawn rules.
(entityType, level, spawnReason, pos, random) -> {
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// Use the appropriate Operation here.
RegisterSpawnPlacementsEvent.Operation.AND
);
}
```

The event also provides two utility overloads (where `spawnPredicate` is the lambda we used earlier):

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, Operation.OR)
event.register(MY_ENTITY.get(), spawnPredicate);
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, operation)
event.register(MY_ENTITY.get(), spawnPredicate, operation);
}
```

### Natural Spawning

_See also [Entities/`MobCategory`][mobcategory], [Worldgen/Biome Modifers/Add Spawns][addspawns], [Worldgen/Biome Modifers/Add Spawn Costs][addspawncosts]; and [Spawn Cycle][spawncycle] on the [Minecraft Wiki][mcwiki]._
Expand Down
67 changes: 67 additions & 0 deletions versioned_docs/version-1.21.4/entities/livingentity.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -216,6 +216,73 @@ DeferredItem<SpawnEggItem> MY_ENTITY_SPAWN_EGG = ITEMS.registerItem("my_entity_s

As an item like any other, the item should be added to a [creative tab][creative], and a [client item][clientitem], [model] and [translation] should be added.

### Spawn Placements

By default, spawning will be possible anywhere, including inside blocks and in midair. To prevent this, a spawn placement must be registered. This happens in the `RegisterSpawnPlacementsEvent` like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// SpawnPlacementType is a functional interface that checks whether a given position is valid
// for spawning. You can add your own SpawnPlacementType if needed,
// see the implementation of SpawnPlacementTypes for reference.
// Vanilla values include NO_RESTRICTIONS, IN_WATER, IN_LAVA and ON_GROUND.
SpawnPlacementTypes.ON_GROUND,
// The heightmap type to use. This provides the initial height to check during world generation,
// later this is ignored and just uses the world surface. Possible values are
// WORLD_SURFACE, OCEAN_FLOOR, MOTION_BLOCKING and MOTION_BLOCKING_NO_LEAVES.
Heightmap.Types.WORLD_SURFACE,
// A predicate to check additional spawn rules, e.g. light. Can either be specified here
// as a lambda, or (more commonly) as a static method in the entity class.
(entityType, level, spawnReason, pos, random) -> {
// Make our mob only spawn on grass blocks.
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// For our own mobs, any operation may be used.
RegisterSpawnPlacementsEvent.Operation.OR
);
}
```

It is also possible to modify vanilla's or other mods' spawn placements. You can use one of `Operation.AND` (for extra spawn restrictions), `Operation.OR` (for alternate spawn mechanisms) or `Operation.REPLACE` (to completely replace the spawn placement, use a [low-priority event listener][priority] in this case) like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// When not using Operation.REPLACE, leave the spawn placement type
// and the heightmap type at null.
null,
null,
// Like above, check the additional/alternate spawn rules.
(entityType, level, spawnReason, pos, random) -> {
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// Use the appropriate Operation here.
RegisterSpawnPlacementsEvent.Operation.AND
);
}
```

The event also provides two utility overloads (where `spawnPredicate` is the lambda we used earlier):

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, Operation.OR)
event.register(MY_ENTITY.get(), spawnPredicate);
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, operation)
event.register(MY_ENTITY.get(), spawnPredicate, operation);
}
```

### Natural Spawning

_See also [Entities/`MobCategory`][mobcategory], [Worldgen/Biome Modifers/Add Spawns][addspawns], [Worldgen/Biome Modifers/Add Spawn Costs][addspawncosts]; and [Spawn Cycle][spawncycle] on the [Minecraft Wiki][mcwiki]._
Expand Down
67 changes: 67 additions & 0 deletions versioned_docs/version-1.21.5/entities/livingentity.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -216,6 +216,73 @@ DeferredItem<SpawnEggItem> MY_ENTITY_SPAWN_EGG = ITEMS.registerItem("my_entity_s

As an item like any other, the item should be added to a [creative tab][creative], and a [client item][clientitem], [model] and [translation] should be added.

### Spawn Placements

By default, spawning will be possible anywhere, including inside blocks and in midair. To prevent this, a spawn placement must be registered. This happens in the `RegisterSpawnPlacementsEvent` like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// SpawnPlacementType is a functional interface that checks whether a given position is valid
// for spawning. You can add your own SpawnPlacementType if needed,
// see the implementation of SpawnPlacementTypes for reference.
// Vanilla values include NO_RESTRICTIONS, IN_WATER, IN_LAVA and ON_GROUND.
SpawnPlacementTypes.ON_GROUND,
// The heightmap type to use. This provides the initial height to check during world generation,
// later this is ignored and just uses the world surface. Possible values are
// WORLD_SURFACE, OCEAN_FLOOR, MOTION_BLOCKING and MOTION_BLOCKING_NO_LEAVES.
Heightmap.Types.WORLD_SURFACE,
// A predicate to check additional spawn rules, e.g. light. Can either be specified here
// as a lambda, or (more commonly) as a static method in the entity class.
(entityType, level, spawnReason, pos, random) -> {
// Make our mob only spawn on grass blocks.
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// For our own mobs, any operation may be used.
RegisterSpawnPlacementsEvent.Operation.OR
);
}
```

It is also possible to modify vanilla's or other mods' spawn placements. You can use one of `Operation.AND` (for extra spawn restrictions), `Operation.OR` (for alternate spawn mechanisms) or `Operation.REPLACE` (to completely replace the spawn placement, use a [low-priority event listener][priority] in this case) like so:

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
event.register(
// The EntityType<?> to register the spawn placement for.
MY_ENTITY.get(),
// When not using Operation.REPLACE, leave the spawn placement type
// and the heightmap type at null.
null,
null,
// Like above, check the additional/alternate spawn rules.
(entityType, level, spawnReason, pos, random) -> {
return level.getBlockState(pos.below()).is(Blocks.GRASS_BLOCK)
|| Mob.checkMobSpawnRules(entityType, level, spawnReason, pos, random);
},
// Use the appropriate Operation here.
RegisterSpawnPlacementsEvent.Operation.AND
);
}
```

The event also provides two utility overloads (where `spawnPredicate` is the lambda we used earlier):

```java
@SubscribeEvent // on the mod event bus
public static void registerSpawnPlacements(RegisterSpawnPlacementsEvent event) {
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, Operation.OR)
event.register(MY_ENTITY.get(), spawnPredicate);
// Identical to event.register(MY_ENTITY.get(), null, null, spawnPredicate, operation)
event.register(MY_ENTITY.get(), spawnPredicate, operation);
}
```

### Natural Spawning

_See also [Entities/`MobCategory`][mobcategory], [Worldgen/Biome Modifers/Add Spawns][addspawns], [Worldgen/Biome Modifers/Add Spawn Costs][addspawncosts]; and [Spawn Cycle][spawncycle] on the [Minecraft Wiki][mcwiki]._
Expand Down
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