Structure Placer API

This simple API provides a simple way to spawn a structure in your world one-time, instead of putting it in the world generation. It could be useful for an item that creates a portal, or some other kind of structure. Or to create LuckyBlocks, who knows!

Setup

Include this library into your build.gradle as a dependency

repositories {
    maven {
        name = "Modrinth"
        url = "https://api.modrinth.com/maven"
        content {
            includeGroup "maven.modrinth"
        }
    }
}

dependencies {
    modImplementation "maven.modrinth:structureplacerapi:<version>"
}

If you want you can include the API in your jar file by adding only the include string:

repositories {
    maven {
        name = "Modrinth"
        url = "https://api.modrinth.com/maven"
        content {
            includeGroup "maven.modrinth"
        }
    }
}

dependencies {
    modImplementation "maven.modrinth:structureplacerapi:<version>"
    include "maven.modrinth:structureplacerapi:<version>"
}

It's less than 25 kb!

How to use it

How to create the structure?

You have to create an NBT structure using minecraft's StructureBlocks, as demonstrated in this video: https://www.youtube.com/watch?v=umhuRXinD3o

Where to put the file I got?

You will need to place the structure.nbt file insde your mod's data folder, like this: data/yourmodid/structures

Creating a new placer object

In order to place the structure, you will need to create a placer object first, this is done simply by creating a new StructurePlacerAPI object. It has quite a few parameters to play with:

StructurePlacerAPI(ServerWorld world, Identifier templateName, BlockPos blockPos, BlockMirror mirror, BlockRotation rotation, boolean ignoreEntities, float integrity, BlockPos offset)

The parameters

• The first parameter world is the wolrd in which we are going to place a structure. You could get it from an entity, or whatever.
• The second parameter templateName is an Identifier made up by the MOD_ID of your mod and the structure's name
• The third parameter blockPos is the block position where your structure is going to spawn. You can get it from an entity coordinates for example
• The fourth, mirror is the first of the optional parameters. With this you can mirror your structure using the BlockMirror class. No need to create another object just type BlockMirror.#stuff
• The fifth, rotation is like the previuous one, and you will be able to rotate your structure using the BlockRotation class. No need to create another object just type BlockMirror.#stuff
• The ignoreEntities parameter if set to true won't spawn entities included inside the structure file. If set to false, it will instead spawn them
• The integrity parameter is pretty intresting, since it is a float value between 0f and 1f which will deteremine how much the structure will be run-down. If set to a value below 1f some of the blocks will be removed upon generation
• Finally, the offset parameter is another BlockPos that could be useful to reposition the structure under an entity's feet or something.

Placing the structure

You have just created a StructurePlacerAPI placer = new StructurePlacerAPI(things up there), and to spawn it you will have to do this:

placer.loadStructure();

Yeah ok it's not that difficult. You just have to run that tho, not the .place method directly, since the load will also check for the existance of said structure before spawning it.

Restoring the old terrein after some time

Starting from version 1.1.0 you can also use:

placer.loadAndRestoreStructure(int restore_ticks);

to supply an amount of ticks ( 1 seconds = 20 ticks ) after which the old terrain will be restored. NOTICE: It could lead to performance issues, especially if the structure is really big! (It needs to save every block inside the structure!)

You can also add an animation for the blocks reappearing by using:

placer.loadAndRestoreStructureAnimated(int restore_ticks, int blocks_per_tick, boolean random);

• blocks_per_ticks is the amaount of blocks that will be replaced each tick, so if your structure is made by 200 blocks, and the blocks_per_ticks is set to 1, it will take 1 second to place 20 blocks, and 20 seconds to finish the terrain restoration.
• random refers to order in which the blocks will be replaced. Setting to true, each time the regenerated block will be a random one, otherwise it will go from one angle of the structure to the other one. In my opinion, random = true is cooler.

Selecting which blocks should be replaced (from 2.0.0 onwards)

You can now specify if the structure that gets placed can replace bedrock and barriers or blocks with a certain tag, or if it can ONLY replace blocks with a certain tag. After you have created you StructurePlacerAPI placer object, ou can use these methods:

/** Sets weather or not this structure should replace the bedrock */
placer.setReplaceBedrock(boolean replaceBedrock)
    
/** Weather or not this structure should replace the barrier block */
placer.setReplaceBarrier(boolean replaceBarrier)

/** Sets weather or not this structure should only replace blocks with the provided tag, for example only replace air blocks */
placer.setOnlyReplaceTaggedBlocks(boolean onlyReplaceTaggedBlocks, TagKey<Block> tag)

/** Allows to specify blocks which won't be replaced if they have the provided tag*/
placer.setPreventReplacementOfTaggedBlocks(boolean preventReplacementOfTaggedBlocks, TagKey<Block> tag)

Performing an action when a certain block is placed with the structure, or replaced by it (2.0.0+)

Now you have the option to execute a function when a block inside a structure gets placed in the world or when a block is replaced while placing the structure.

For example, if you want a random fox to spawn when placing a structure containing berry bushes you can use:

placer.actionOnBlocksPlacedByStructure(ActionOnBlockFind action, TagKey<Block> targets);

//Example:
placer.actionOnBlocksPlacedByStructure((info, world) -> {world.spawnEntity(EntityType.FoxEntity, ...)}, BlockTags.BUSHES);

The action is a lambda function that provides you with the StructureBlockInfo and ServerWorldAccess (or ServerLevelAccess or whatever it is with mojmaps). You have to specify a tag for the kind of block you want to replace. If it's only a single block type create a Tag for that block.

The other thing you can do is execute something when a block that is already in the world gets replaced by the structure. Like spawning snow particles when an ice block is replaced:

placer.actionOnBlocksReplacedByStructure(ActionOnBlockFind action, TagKey<Block> targets);

//Example:
placer.actionOnBlocksReplacedByStructure((info, world) -> {world.spawnParticles(ParticleType.SNOW, ...)}, BlockTags.ICE);

Example

An example of this could be the one you find insde the LightWithin mod(whihc btw, you should check out):

StructurePlacer placer = new StructurePlacer((ServerWorld) caster.getWorld(), new Identifier(MOD_ID, "frost_light"), caster.getBlockPos(), BlockMirror.NONE, BlockRotation.CLOCKWISE_90, true, 1.0f, new BlockPos(-4, -3, -3));
placer.loadStructure();

To have a permanent structure

StructurePlacer placer = new StructurePlacer((ServerWorld) caster.getWorld(), new Identifier(MOD_ID, "frost_light"), caster.getBlockPos(), BlockMirror.NONE, BlockRotation.CLOCKWISE_90, true, 1.0f, new BlockPos(-4, -3, -3));
placer.loadAndRestoreStructureAnimated(200, 2, true);

To make the old terrain regenerate by replacing two blocks per tick, in a random order.

Warning!

IMPORTANT! MAKE SURE YOU ARE ON THE SERVER THREAD!

if(!world.isClient){
//run stuff
}

Support me

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License

This API is available under the CC0 license. Feel free to learn from it and incorporate it in