This preview introduces entity spawn rules and unifies the spawn-related fields in item behaviour components that involve placing entities.

For a few more details regarding the split and future you can look at the roadmap to 1.21!

Changes

Item Behaviour Components

minecraft:bucket

• Replaced the entity field with an entity spawner instead of just the entity type.

So if you had this:

{
  "minecraft:bucket": {
    "entity": "minecraft:pufferfish",
    "modification": {
      "type": "minecraft:place_fluid",
      "fluid": "minecraft:water",
      "place_sound": "minecraft:item.bucket.empty_fish",
      "transforms_into": "minecraft:bucket"
    }
  }
}

You now have to use this:

{
  "minecraft:bucket": {
    "entity": {
      "entity": "minecraft:pufferfish"
    },
    "modification": {
      "type": "minecraft:place_fluid",
      "fluid": "minecraft:water",
      "place_sound": "minecraft:item.bucket.empty_fish",
      "transforms_into": "minecraft:bucket"
    }
  }
}

minecraft:entity

• Merged the entity and allow_item_data fields into a single entity field by using an entity spawner.
• Added allow_spawner_modification.
  • Its value is an optional boolean defaulting to false.
  • Determines whether the item can modify a Spawner's entity type.

So if you had this:

{
  "minecraft:entity": {
    "allow_item_data": true,
    "entity": "minecraft:pig",
    "passes": [
      "block",
      "fluid"
    ]
  }
}

You now have to use this:

{
  "minecraft:entity": {
    "allow_spawner_modification": true,
    "entity": {
      "allow_item_data": true,
      "entity": "minecraft:pig"
    },
    "passes": [
      "block",
      "fluid"
    ]
  }
}

minecraft:projectile

• Expanded the entity field by adding optional spawn rules, an optional spawn sound and whether to allow item data or not.

minecraft:spawn_egg

• Is no longer required for Spawner entity type modification.
  • This field has instead been moved to the minecraft:entity item behaviour component.
• The behaviour component is still used for spawning children when used on the specified entity type.

So if you had this:

{
  "minecraft:entity": {
    "allow_item_data": true,
    "entity": "minecraft:pig",
    "passes": [
      "block",
      "fluid"
    ]
  },
  "minecraft:spawn_egg": {}
}

You now have to use this:

{
  "minecraft:entity": {
    "allow_spawner_modification": true,
    "entity": {
      "allow_item_data": true,
      "entity": "minecraft:pig"
    },
    "passes": [
      "block",
      "fluid"
    ]
  },
  "minecraft:spawn_egg": {}
}

Entity Spawners

• Spawns an entity using the specified rules.
• Fields:
  • entity: An entity type. The entity type to spawn.
    • If allow_item_data is set to true, the entity type may additionally be determined via the minecraft:entity_data data component from the used item stack, which takes precedence over the entity field.
  • spawn_rules: An optional list of spawn rules. The spawn rules to apply in the specified order.
  • components: An optional set of components. The components to apply to the spawned entity.
  • spawn_sound: An optional sound event. The sound to play when the entity is spawned.
  • allow_item_data: An optional boolean defaulting to false. Whether to allow item data from the minecraft:entity_data data component from the used item stack.

Entity Spawn Rules

• Determines whether to place the entity or not and if so, its position and rotation.
• Rules are applied when the condition passes or when no condition is specified.
• Common fields:
  • condition: An optional predicate. Determines whether to apply the rule or not.

minecraft:align_yaw

• Aligns the entity's yaw based on the placer's own yaw using the specified amount of steps.
• Fields:
  • step: An integer ranging from 2 to 360. The amount of steps.
    • For example, a value of 8 rounds to the nearest 45 degree as 360 / 8 = 45.

Example:

{
  "type": "minecraft:align_yaw",
  "steps": 8
}

minecraft:discard

• Discards the entity entirely.
• Has no additional fields.

Example:

{
  "type": "minecraft:discard",
  "condition": {
    "condition": "minecraft:side_check",
    "sides": [
      "down"
    ]
  }
}

minecraft:fits_in_volume

• Checks whether the specified hitbox or otherwise entity's default hitbox fits in the specified volume.
• The hitbox to check for is centred around the entity spawner's current spawn position.
• Fields:
  • blocks: An optional boolean. Defaults to true. Whether to check if the entity fits inside the surrounding blocks.
  • entities: An optional boolean. Defaults to true. Whether to check if the entity fits inside the surrounding entities.
  • volume: An optional list of three doubles. The volume to use instead of the entity's hitbox.

Example:

{
  "type": "minecraft:fits_in_volume",
  "blocks": false,
  "volume": [
    1.0,
    2.0,
    1.0
  ]
}

minecraft:offset_spawn_position

• Offsets the entity's spawn position by the specified amount.
• Fields:
  • offset: A list of three doubles. The position offset.

{
  "type": "minecraft:offset_spawn_position",
  "offset": [
    0.0,
    0.0625,
    0.0
  ]
}

Fixes

• Fixed the world modification type registry name.