DockyardMC

Appearance

Layering Entity Metadata ​

How it works ​

Layering entity metadata per player allows for client-side changes to entities for purposes like client-side glowing and client-side invisibility

It works like this:

  • Entity has one base BindableMap<EntityMetadataType, EntityMetadata>
  • Entity also has metadataLayers which is BindableMap<PersistentPlayer, MutableMap<EntityMetadataType, EntityMetadata>
  • When ClientboundSetEntityMetadataPacket is gets created, it looks up the metadata layers and gets layer of the receiving player.
  • It merges player`s layer on top of entity's base metadata and that gets sent to the player

INFO

metadataLayers uses PersistentPlayer as the key in the map meaning it will remain and still work when player disconnects and re-connects

Usage ​

kotlin
// Spawn an entity
val entity = world.spawnEntity(Pig(location, world))

// get the metadata layer of player or create new one if it doesn't exist
val playerMetadataLayer = entity.metadataLayers[player.toPersistent()] ?: mutableMapOf<EntityMetadataType, EntityMetadata>()

// create metadata with EntityMetaIndex.STATE and EntityMetadataType.BYTE that contains things like isGlowing, isInvisible etc.
// I use utility function here because state requires bitmask of values, this makes it easier
val entityState = getEntityMetadataState(entity) {
    isGlowing = true
}
// add the metadata to the list 
playerMetadataLayer[EntityMetadataType.STATE] = entityState

// set players layer on that entity to the list of metadata
// use player.toPersistent() because the entity uses PersistentPlayer to store this information
entity.metadataLayers[player.toPersistent()] = playerMetadataLayer

With the example above, the entity will glow only for the specified player. For setting clientside glowing or invisibility, you can also use entity.setGlowingFor(player, true) or entity.setInvisibleFor(player, true) which will do all of this automatically for you

kotlin
// spawn warden
val warden = world.spawnEntity(Warden(location, world))

// get the metadata layer of player or create new one if it doesn't exist
val playerMetadataLayer = warden.metadataLayers[player.toPersistent()] ?: mutableMapOf<EntityMetadataType, EntityMetadata>()

// create new EntityMetadata with index and type pose
val pose = EntityMetadata(EntityMetadataType.POSE, EntityMetadataByteBufWriter.POSE, EntityPose.ROARING)

// add the pose to the list
playerMetadataLayer[EntityMetadataType.POSE] = pose
warden.metadataLayers[player.toPersistent()] = playerMetadataLayer

With the example above you can make the specified player see the warden roaring!

To remove a metadata from layer, you can simply use MutableMap<EntityMetadataType, EntityMetadata>.remove(entityMetaIndex) like you would do with any mutable map:

kotlin
warden.metadataLayers[player.toPersistent()]?.remove(EntityMetaIndex.POSE)

You can also remove the entire layer with:

kotlin
entity.metadataLayers.remove(player.toPersistent())