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finnsetchell edited this page Dec 12, 2025 · 1 revision

Jigsaw Structure Example: Barn

This walkthrough demonstrates creating a jigsaw structure using the Barn structure from MoogsVoyagerStructures. Jigsaw structures can expand and connect multiple pieces together.

Overview

The Barn structure demonstrates:

  • Simple jigsaw connections
  • Terrain height checks
  • Exclusion zones
  • Multiple template pools

While the barn itself is simple, it shows how jigsaw systems work.

File Structure

data/mvs/
├── structure/
│   └── houses/
│       └── barn.nbt
└── worldgen/
    ├── structure/
    │   └── barn.json
    ├── structure_set/
    │   └── barn.json
    └── template_pool/
        └── houses/
            └── barn/
                └── start_pool.json

Step 1: Create the NBT File

  1. Build your barn structure in Minecraft
  2. Add Jigsaw Blocks where you want connections:
    • Place jigsaw blocks at connection points
    • Set jigsaw block properties:
      • Name: Pool to connect to (e.g., mvs:barn/side_pool)
      • Target: Jigsaw block name in target pieces (e.g., barn_side)
      • Joint: rollable (usually)
  3. Save as barn.nbt
  4. Place at: data/mvs/structure/houses/barn.nbt

Note: For this example, the barn is simple and may not have side pools, but the structure supports jigsaw expansion.

Step 2: Create the Template Pool

File: data/mvs/worldgen/template_pool/houses/barn/start_pool.json

{
  "name": "mvs:barn/start_pool",
  "fallback": "minecraft:empty",
  "elements": [
    {
      "weight": 1,
      "element": {
        "location": "mvs:houses/barn",
        "processors": "minecraft:empty",
        "projection": "rigid",
        "element_type": "minecraft:single_pool_element"
      }
    }
  ]
}

Explanation

  • name: "mvs:barn/start_pool" - Pool identifier
  • location: "mvs:houses/barn" - References data/mvs/structure/houses/barn.nbt
  • If the barn NBT has jigsaw blocks, they reference other pools (like side pools)

Optional: Side Pool Example

If your barn has side pieces, create additional pools:

File: data/mvs/worldgen/template_pool/houses/barn/side_pool.json

{
  "name": "mvs:barn/side_pool",
  "fallback": "minecraft:empty",
  "elements": [
    {
      "weight": 1,
      "element": {
        "location": "mvs:houses/barn_side_left",
        "processors": "minecraft:empty",
        "projection": "rigid",
        "element_type": "minecraft:single_pool_element"
      }
    },
    {
      "weight": 1,
      "element": {
        "location": "mvs:houses/barn_side_right",
        "processors": "minecraft:empty",
        "projection": "rigid",
        "element_type": "minecraft:single_pool_element"
      }
    }
  ]
}

Jigsaw blocks in the main barn would reference mvs:barn/side_pool to connect these pieces.

Step 3: Create the Structure JSON

File: data/mvs/worldgen/structure/barn.json

{
  "type": "moogs_structures:moogs_structures_generic_jigsaw_structure",
  "start_pool": "mvs:houses/barn/start_pool",
  "size": 1,
  "biomes": "#mvs:has_structure/overworld_biomes",
  "project_start_to_heightmap": "WORLD_SURFACE_WG",
  "cannot_spawn_in_liquid": true,
  "terrain_height_radius_check": 1,
  "allowed_terrain_height_range": 3,
  "step": "surface_structures",
  "terrain_adaptation": "beard_thin",
  "start_height": {
    "absolute": 0
  },
  "spawn_overrides": {}
}

Key Differences from Simple Structure

Terrain Height Checks

{
  "terrain_height_radius_check": 1,
  "allowed_terrain_height_range": 3
}

What this does:

  • Checks terrain height in a 1-chunk radius around the structure
  • Only spawns if terrain height varies by 3 blocks or less
  • Prevents barns from spawning on steep hills or cliffs

Why: Barns should spawn on relatively flat terrain.

Field-by-Field Explanation

  • type: Generic jigsaw structure (supports expansion)
  • start_pool: References the barn start pool
  • size: 1 - Minimal expansion (barn is simple)
  • terrain_height_radius_check: 1 - Check 1 chunk radius
  • allowed_terrain_height_range: 3 - Max 3 block height difference
  • Other fields same as simple structure

Step 4: Create the Structure Set

File: data/mvs/worldgen/structure_set/barn.json

{
  "structures": [
    {
      "structure": "mvs:barn",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 766544243,
    "super_exclusion_zone": {
      "chunk_count": 3,
      "other_set": "#mvs:common_avoid"
    },
    "spacing": 31,
    "separation": 26
  }
}

Key Feature: Exclusion Zone

{
  "super_exclusion_zone": {
    "chunk_count": 3,
    "other_set": "#mvs:common_avoid"
  }
}

What this does:

  • Prevents barns from spawning within 3 chunks of structures in #mvs:common_avoid tag
  • Keeps barns away from common structures like houses and carts
  • Creates better structure distribution

Structure Set Tag: data/mvs/tags/worldgen/structure_set/common_avoid.json

{
  "values": [
    "mvs:house",
    "mvs:cart",
    "mvs:well"
  ]
}

Field-by-Field Explanation

  • structures: Single barn structure
  • placement: Advanced random spread
    • salt: Unique identifier
    • super_exclusion_zone: Avoids common structures
    • spacing: 31 chunks average distance
    • separation: 26 chunks minimum distance

How Jigsaw Expansion Works

Even though this barn uses size: 1, here's how jigsaw expansion would work:

  1. Start Pool places the main barn piece
  2. Jigsaw Blocks in the barn NBT file reference other pools
  3. Target Pools (like side pools) provide pieces to connect
  4. Structure Expands until:
    • size limit is reached
    • No more jigsaw connections available
    • max_distance_from_center limit reached

Example Expansion Flow

Start Pool (barn.nbt)
  ↓
Jigsaw Block: "mvs:barn/side_pool" → "barn_side"
  ↓
Side Pool selects piece (barn_side_left.nbt or barn_side_right.nbt)
  ↓
New piece connects to jigsaw block
  ↓
Process repeats until size limit

Testing Your Structure

  1. Create a new world with your datapack/mod
  2. Use /locate structure mvs:barn to find barns
  3. Verify:
    • Spawns on relatively flat terrain
    • Not near other common structures (exclusion zone working)
    • Proper spacing between barns
    • Terrain height checks working

Common Issues

Structure Not Spawning

Check:

  • Terrain height restrictions might be too strict
  • Exclusion zone might be blocking all locations
  • Biome tags correct

Spawning on Steep Terrain

Solution: Increase allowed_terrain_height_range or adjust terrain_height_radius_check

Too Close to Other Structures

Solution: Increase chunk_count in exclusion zone or adjust spacing/separation

Advanced: Multiple Variants

To have multiple barn variants:

Template Pool:

{
  "elements": [
    {
      "weight": 3,
      "element": {
        "location": "mvs:houses/barn",
        ...
      }
    },
    {
      "weight": 1,
      "element": {
        "location": "mvs:houses/barn_large",
        ...
      }
    }
  ]
}

Large barns spawn 1/3 as often as regular barns.

Advanced: Jigsaw Expansion

To allow barn expansion:

Structure JSON:

{
  "size": 5,
  "max_distance_from_center": 20
}

Create Side Pools:

  • barn/side_pool.json - Side pieces
  • barn/corner_pool.json - Corner pieces
  • barn/roof_pool.json - Roof variations

Add Jigsaw Blocks in NBT files to connect pieces.

Next Steps

Now that you understand jigsaw structures:

  1. Nether Structure Example - Nether-specific features
  2. Complex Structure Example - Large expanding structures
  3. Advanced Topics - Advanced features

See Also:

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