Custom multiblocks

RebarSimpleMultiblock is very useful and suitable for most multiblocks. However, on occasion you may want more flexibility. A simple example would be the fluid tank; a multiblock which can have 0-8 multiblock tank casings on top of it. Obviously, this is not suitable for regular RebarSimpleMultiblock.

This can be accomplished using RebarMultiblock, which RebarSimpleMultiblock is built on top of. At its core, the multiblock system is just a change detection system which listens for blocks being placed or broken, and notifies your multiblock if it has had a component placed or broken. In order to do this, the change detection system requires you to provide:

  • A list of chunks which the multiblock spans
  • A function which returns whether a given block is part of the multiblock

To provide these, your multiblock must implement getChunksOccupied and isPartOfMultiblock. For example:

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@Override
public @NotNull Set<@NotNull ChunkPosition> getChunksOccupied() {
    return Set.of(new ChunkPosition(getBlock().getChunk()));
}

@Override
public boolean isPartOfMultiblock(@NotNull Block otherBlock) {
    return otherBlock.equals(getBlock().getRelative(BlockFace.DOWN));
}

Note that isPartOfMultiblock must return true if the block could potentially be part of the multiblock, so you should not be doing any checks for the type of block - just the position! For example, if your multiblock needs a fire in the block below it, then isPartOfMultiblock should ALWAYS return true if the block below your multiblock is supplied to it.

Additionally, you must implement checkFormed, for example:

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@Override
public boolean checkFormed() {
    Block belowBlock = getBlock().getRelative(BlockFace.DOWN);
    return !BlockStorage.isRebarBlock(belowBlock) && belowBlock.getType() == Material.FIRE;
}

This will be called whenever a block that is part of your multiblock (i.e. is within the chunks supplied by getChunksOccupied and satisfies isPartOfMultiblock) is modified. It can be thought of as a 'refresh' function which makes sure that the multiblock is still constructed correctly.

RebarMultiblock still comes with the isFormedAndFullyLoaded, onMultiblockFormed, and onMultiblockUnformed methods, which are useful for implementing your own multiblock management logic.

Obviously, this is extremely barebones. You will need to implement simple concepts like rotation yourself - you may wish to look at source code of RebarSimpleMultiblock to make this easier.

Finally, if you want to give your custom multiblock ghost blocks like RebarSimpleMultiblock, you can use RebarGhostBlockHolder. This automatically manages ghost blocks. You can create a new ghost block with addGhostBlock and remove a ghost block with removeGhostBlock.