Block Entities

Tile entities are like simplified entities that are bound to a Block. They are used to store dynamic data, execute tick based tasks and for dynamic rendering. Some examples from vanilla Minecraft would be: handling of inventories (chests), smelting logic on furnaces, or area effects for beacons. More advanced examples exist in mods, such as quarries, sorting machines, pipes, and displays.

Tip

A TileEntity isn’t a solution for everything, and they can cause lag when used wrongly. When possible, try to avoid them.

Creating a TileEntity

In order to create a TileEntity you need to extend the TileEntity class. To register it, listen for the appropriate registry event and create a TileEntityType:

@SubscribeEvent
public static void registerTE(RegistryEvent.Register<TileEntityType<?>> evt) {
  TileEntityType<?> type = TileEntityType.Builder.create(factory, validBlocks).build(null);
  type.setRegistryName("examplemod", "myte");
  evt.getRegistry().register(type);
}

You can also use a DeferredRegister instead.

public static final DeferredRegister<TileEntityType<?>> TILE_ENTITIES = DeferredRegister.create(ForgeRegistries.TILE_ENTITIES, "examplemod");

public static final RegistryObject<TileEntityType<?>> MY_TE = TILE_ENTITIES.register("myte", () -> TileEntityType.Builder.create(factory, validBlocks).build(null));

In this example, factory is a function that creates a new instance of your TileEntity. A method reference or a lambda is commonly used. The variable validBlocks is one or more blocks (TileEntityType$Builder::create is varargs) that the tile entity can exist for.

Attaching a TileEntity to a Block

To attach your new TileEntity to a Block you need to override 2 (two) methods within the Block class.

IForgeBlock#hasTileEntity(BlockState state)

IForgeBlock#createTileEntity(BlockState state, IBlockReader world)

Using the parameters you can choose if the block should have a TileEntity or not. Usually you will return true in the first method and a new instance of your TileEntity in the second method.

Storing Data within your TileEntity

In order to save data, override the following two methods TileEntity#write(CompoundNBT nbt)

TileEntity#read(BlockState state, CompoundNBT nbt) These methods are called whenever the Chunk containing the TileEntity gets loaded from/saved to NBT. Use them to read and write to the fields in your tile entity class.

Tip

Whenever your data changes you need to call TileEntity#markDirty(), otherwise the Chunk containing your TileEntity might be skipped while the world is saved.

Important

It is important that you call the super methods!

The tag names id, x, y, z, ForgeData and ForgeCaps are reserved by the super methods.

Ticking TileEntity

If you need a ticking TileEntity, for example to keep track of the progress during a smelting process, you need to add the ITickableTileEntity interface to your TileEntity. Now you can implement all your calculations within

ITickableTileEntity#tick()

Tip

This method is called each tick. Therefore, you should avoid having complicated calculations in here. If possible, you should make more complex calculations just every X ticks. (The amount of ticks in a second may be lower than 20 (twenty) but won’t be higher)

Synchronizing the Data to the Client

There are 3 (three) ways of syncing data to the client. Synchronizing on chunk load, synchronizing on block updates and synchronizing with a custom network message.

Synchronizing on chunk load

For this you need to override

TileEntity#getUpdateTag()

IForgeTileEntity#handleUpdateTag(BlockState state, CompoundNBT tag)

Again, this is pretty simple, the first method collects the data that should be send to the client, while the second one processes that data. If your TileEntity doesn’t contain much data you might be able to use the methods out of the Storing Data section.

Important

Synchronizing excessive/useless data for tile entities can lead to network congestion. You should optimize your network usage by sending only the information the client needs when the client needs it. For instance, it is more often than not unnecessary to send the inventory of a tile entity in the update tag, as this can be synchronized via its GUI.)

Synchronizing on block update

This method is a bit more complicated, but again you just need to override 2 methods. Here is a tiny example implementation of it

@Override
public SUpdateTileEntityPacket getUpdatePacket(){
    CompoundNBT nbtTag = new CompoundNBT();
    //Write your data into the nbtTag
    return new SUpdateTileEntityPacket(getPos(), -1, nbtTag);
}

@Override
public void onDataPacket(NetworkManager net, SUpdateTileEntityPacket pkt){
    CompoundNBT tag = pkt.getNbtCompound();
    //Handle your Data
}

The Constructor of SUpdateTileEntityPacket takes:

• The position of your TileEntity.
• An ID, though it isn’t really used besides by Vanilla, therefore you can just put a -1 in there.
• An CompoundNBT which should contain your data.

Now, to send the packet, an update notification must be given on the server. World#notifyBlockUpdate(BlockPos pos, BlockState oldState, BlockState newState, int flags) The pos should be your TileEntity’s position. For oldState and newState you can pass the current BlockState at that position. The flags are a bitmask and should contain 2, which will sync the changes to the client. See Constants$BlockFlags for more info as well as the rest of the flags. The flag 2 is equivalent to Constants$BlockFlags#BLOCK_UPDATE.

Synchronizing using a custom network message

This way of synchronizing is probably the most complicated one, but is usually also the most optimized one, as you can make sure that only the data you need to be synchronized is actually synchronized. You should first check out the Networking section and especially SimpleImpl before attempting this. Once you’ve created your custom network message, you can send it to all users that have the TileEntity loaded with:

SimpleChannel#send(PacketDistributor.TRACKING_CHUNK.with(() -> chunk), MSG);

Alert

It is important that you do safety checks, the TileEntity might already be destroyed/replaced when the message arrives at the player! You should also check if the area is loaded using (World#isAreaLoaded(BlockPos, int))