adding-structures-1.18-1.19

Source: https://misode.github.io/guides/adding-custom-structures 
License: MIT, Copyright (c) 2020 Misode

This guide will showcase how to create a data pack that adds a custom structure to the world. There is also a [data pack download]({#[1.18.2] https://gist.github.com/misode/45559d34627755ecaa52497daea83544/raw/8ece848257e6ce17769ca17eccdf89b5889afbe2/tall-towers-1.18.2.zip #}{#[1.19] https://gist.github.com/misode/45559d34627755ecaa52497daea83544/raw/b7d7c44a132641d308cbdc93ce4cf061759d15c5/tall-towers-1.19.zip #}) of this complete example.

Always leave the world and rejoin to apply the new changes!

Pack.mcmeta

Like every data pack, we need a pack.mcmeta. In this version, the pack format is {#pack_format#}.

{
  "pack": {
    "pack_format": {#pack_format#},
    "description": "A tall tower"
  }
}

The structure set

A structure set is where the placement starts. It defines where in the world the structure should be placed, and how rare it is. It takes a weighted list of different structures, allowing structure variants (for example the vanilla nether has a structure set with both the bastion and fortress).

data/example/worldgen/structure_set/tall_towers.json

{
  "structures": [
    {
      "structure": "example:tall_tower",
      "weight": 1
    }
  ],
  "placement": {
    "type": "minecraft:random_spread",
    "spacing": 5,
    "separation": 2,
    "salt": 1646207470
  }
}

Structure sets are made up of two parts:

• fstructures: A weighted list of configured structure features [(see next step)](#the{#[1.18.2] -configured #}-structure).
• fplacement: The structure placement
  • ftype: Either srandom_spread or sconcentric_rings. The latter is only used by strongholds in vanilla, so we'll focus on srandom_spread
  • fspacing: Roughly the average distance in chunks between two structures in this set.
  • fseparation: The minimum distance in chunks. Needs to be smaller than spacing.
  • fsalt: A random number that is combined with the world seed. Always use a different random number for different structures, otherwise they will end up being placed in the same spot!

When using the srandom_spread placement type, it generates structures grid-based. Here's an illustration of the above example with spacing = 5, separation = 2. There will be one structure attempt in each 5x5 chunk grid, and only at X a structure can spawn.

.............
..XXX..XXX..X
..XXX..XXX..X
..XXX..XXX..X
.............
.............
..XXX..XXX..X
..XXX..XXX..X
..XXX..XXX..X

The {#[1.18.2] configured structure #}{#[1.19] structure #}

The {#[1.18.2] configured structure (feature) #}{#[1.19] structure #} is the ID you will be able to reference in /locate.

data/example/worldgen/{#[1.18.2] configured_structure_feature #}{#[1.19] structure #}/tall_tower.json

{#[1.18.2]
{
  "type": "minecraft:village",
  "config": {
    "start_pool": "example:tall_tower",
    "size": 1
  },
  "biomes": "#minecraft:has_structure/mineshaft",
  "adapt_noise": true,
  "spawn_overrides": {}
}
#}{#[1.19]
{
  "type": "minecraft:jigsaw",
  "biomes": "#minecraft:has_structure/mineshaft",
  "step": "surface_structures",
  "spawn_overrides": {},
  "terrain_adaptation": "beard_thin",
  "start_pool": "example:tall_tower",
  "size": 1,
  "start_height": {
    "absolute": 0
  },
  "project_start_to_heightmap": "WORLD_SURFACE_WG",
  "max_distance_from_center": 80,
  "use_expansion_hack": false
}
#}

Let's go over all the fields. {#[1.18.2]

• ftype: This is the structure feature type. When making custom structures, you almost always want to set this to svillage or sbastion_remnant. There is one important difference between the two: using svillage will spawn the structure on the surface, while sbastion_remnant will always spawn the structure at Y=33.
• fconfig:
  • fstart_pool: This is a reference to the template pool (see next step).
  • fsize: This is a number between 1 and 7. This is important if your structure uses jigsaw. In this simple example, we'll leave it at 1.
• fbiomes: This controls in which biomes this structure is allowed to generate. You can give it any biome tag, a list of biomes, or a single biome. For easy testing we'll set it to every biome with mineshafts.
• fadapt_noise: When true, it will add extra terrain below each structure piece.
• fspawn_overrides: This field allows you to override mob spawning inside the structure bounding boxes. This is outside the scope of this guide, but you could look at the vanilla monument structure feature as a reference. #}{#[1.19]
• ftype: This is the structure type. When making custom structures, you almost always want to set this to sjigsaw.
• fbiomes: This controls in which biomes this structure is allowed to generate. You can give it any biome tag, a list of biomes, or a single biome. For easy testing we'll set it to every biome with mineshafts.
• fstep: The generation step to place the features in. This matches the steps in a biome's feature list. Possible values: sraw_generation, slakes, slocal_modifications, sunderground_structures, ssurface_structures, sstrongholds, sunderground_ores, sunderground_decoration, sfluid_springs, svegetal_decoration, and stop_layer_modification.
• fterrain_adaptation: Controls how the structure will affect the terrain. It has 4 options:
  • snone: (default) No effect on the terrain.
  • sbeard_thin: Adds terrain below the structure and removes inside the structure. This is what villages use.
  • sbeard_box: Stronger version of sbeard_thin. This is what ancient cities use.
  • sbury: Adds terrain completely around the structure. This is what strongholds use.
• fspawn_overrides: This field allows you to override mob spawning inside the structure bounding boxes. This is outside the scope of this guide, but you could look at the vanilla monument structure feature as a reference.
• fstart_pool: This is a reference to the template pool (see next step).
• fsize: This is a number between 1 and 7. This is important if your structure uses jigsaw. In this simple example, we'll leave it at 1.
• fstart_height: A height provider specifying at which height the structure should spawn. The example uses the constant shorthand so it just specifies a vertical anchor. If used together with fproject_start_to_heightmap, will offset the height relative to the heightmap.
• fproject_start_to_heightmap: An optional heightmap type. Possible values: sWORLD_SURFACE_WG, sWORLD_SURFACE, sOCEAN_FLOOR_WG, sOCEAN_FLOOR, sMOTION_BLOCKING, and sMOTION_BLOCKING_NO_LEAVES.
• fmax_distance_from_center: Value between 1 and 128. The maximum distance that a jigsaw can branch out.
• fuse_expansion_hack: You should always set this to false. Vanilla villages set this to true to fix an issue with their streets. #}

The template pool

The template pool defines how to build up your structure. Since we're not using jigsaw, this is quite straight forward: we want to place a single NBT structure.

data/example/worldgen/template_pool/tall_tower.json

{
  "name": "example:tall_tower",
  "fallback": "minecraft:empty",
  "elements": [
    {
      "weight": 1,
      "element": {
        "element_type": "minecraft:single_pool_element",
        "location": "example:stone_tall_tower",
        "projection": "rigid",
        "processors": "minecraft:empty"
      }
    }
  ]
}

Again, let's go over the fields:

• fname: For some reason, the game needs the name of this template pool. Just set this to the ID of the template pool.
• ffallback: Used in jigsaw structures, but we can simply use sminecraft:empty.
• felements: A weighted list of pool elements to choose from. You can add multiple elements here if your structure has different starting structure files. For example in vanilla a plains village has different town center variants.
  • felement_type: The type of this element. One of sempty_pool_element (placing nothing), sfeature_pool_element (placing a placed feature), slegacy_single_pool_element, slist_pool_element, and ssingle_pool_element (placing a structure).
  • flocation: The path to the structure NBT file. (see next step).
  • fprojection: Either srigid or sterrain_matching. Use the latter if you want the structure to match the terrain, just like village paths do.
  • fprocessors: If you want to run any processor lists, this is quite complicated so again we'll skip this for now and set it to sminecraft:empty.

The structure NBT

Creating the structure NBT file is entirely up to you. In this example I'm going to use a tower structure from Gamemode 4.

data/example/structures/stone_tall_tower.nbt

(binary NBT file) Download the structure from this example

Result