Structure Sets

Structure Sets

Structure sets group structures together and define where and how often they spawn in the world. They're the final piece that connects your structure to world generation.

What are Structure Sets?

Structure sets are collections of structures with shared placement rules. They tell Minecraft:

• Which structures can spawn
• How often they spawn
• Where they spawn (spacing, exclusion zones, etc.)

File Location

Structure sets are stored in:

data/<namespace>/worldgen/structure_set/<name>.json

Example: data/mvs/worldgen/structure_set/cart.json

Basic Structure Set

Every structure set JSON has this structure:

{
  "structures": [
    {
      "structure": "namespace:structure_name",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 123456789,
    "spacing": 34,
    "separation": 26
  }
}

Required Fields

structures

Type: Array of Structure Objects
Example: See below

List of structures that belong to this set. Each structure has:

structure

Type: Resource Location (String)
Example: "mvs:cart"

Reference to a structure JSON file. Must match a structure defined in worldgen/structure/.

weight

Type: Integer
Example: 1

Selection weight if multiple structures are in the set. Higher weights are more likely to be selected.

Example: With weights [1, 2], the second structure is twice as likely to spawn.

placement

Type: Placement Object
Example: See Placement Systems page

Defines how structures are placed in the world. For Moogs Structure Lib, use moogs_structures:advanced_random_spread.

See Placement Systems for complete placement documentation.

Simple Example: Cart

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

{
  "structures": [
    {
      "structure": "mvs:cart",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 203698201,
    "spacing": 34,
    "separation": 26
  }
}

This structure set:

• Contains one structure (mvs:cart)
• Uses advanced random spread placement
• Spawns approximately every 34 chunks
• Keeps at least 26 chunks between instances

Multiple Structures Example

You can include multiple structures in one set:

{
  "structures": [
    {
      "structure": "mvs:house_variant_1",
      "weight": 3
    },
    {
      "structure": "mvs:house_variant_2",
      "weight": 2
    },
    {
      "structure": "mvs:house_variant_3",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 123456789,
    "spacing": 20,
    "separation": 15
  }
}

When a structure spawns, variant 1 is 3x more likely than variant 3.

With Exclusion Zone: Barn

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
  }
}

The super_exclusion_zone prevents barns from spawning within 3 chunks of any structure in the #mvs:common_avoid tag.

Rare Structure: Crystal

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

{
  "structures": [
    {
      "structure": "mvs:crystal",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 469982354,
    "spacing": 112,
    "separation": 62,
    "min_distance_from_world_origin": 800
  }
}

This structure set:

• Spawns very rarely (112 chunks spacing ≈ 1792 blocks)
• Requires at least 800 blocks from world spawn
• Creates a rare, distant structure

Complex Structure: Cathedral

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

{
  "structures": [
    {
      "structure": "mvs:cathedral",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 303685798,
    "spacing": 105,
    "separation": 98,
    "min_distance_from_world_origin": 1000
  }
}

Large, rare structures often use:

• High spacing values (105 chunks ≈ 1680 blocks)
• High separation (98 chunks ≈ 1568 blocks)
• Minimum distance from spawn (1000 blocks)

Nether Structure: Nether Devil

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

{
  "structures": [
    {
      "structure": "mvs:nether_devil",
      "weight": 1
    }
  ],
  "placement": {
    "type": "moogs_structures:advanced_random_spread",
    "salt": 513238798,
    "spacing": 64,
    "separation": 16
  }
}

Nether structures typically use:

• Moderate spacing (64 chunks ≈ 1024 blocks)
• Lower separation (16 chunks ≈ 256 blocks)
• No exclusion zones (Nether is less crowded)

Understanding Placement Values

Spacing

Example: "spacing": 34

Average chunks between structure attempts. Higher = rarer structures.

Important: Moogs Structure Lib multiplies spacing by 1.65 internally. So your spacing: 34 becomes 56.1 chunks internally (~897 blocks).

Conversion: 1 chunk = 16 blocks. Your specified spacing 34 = ~544 blocks, but internally becomes ~897 blocks after the 1.65x multiplier.

Separation

Example: "separation": 26

Minimum chunks between structures. Must be less than spacing.

Important:

• spacing must be greater than separation, otherwise structures can't spawn!
• Moogs Structure Lib multiplies separation by 1.65 internally. So your separation: 26 becomes 42.9 chunks internally (~686 blocks).

Conversion: 1 chunk = 16 blocks. Your specified separation 26 = ~416 blocks, but internally becomes ~686 blocks after the 1.65x multiplier.

Salt

Example: "salt": 203698201

Unique number for this structure set. Affects which chunks are selected for spawning.

Tip: Use random large numbers. Each structure set should have a unique salt.

Common Patterns

Common Structures

For structures that should spawn frequently:

{
  "placement": {
    "spacing": 20,
    "separation": 15
  }
}

Uncommon Structures

For moderately rare structures:

{
  "placement": {
    "spacing": 50,
    "separation": 35
  }
}

Rare Structures

For very rare structures:

{
  "placement": {
    "spacing": 100,
    "separation": 80,
    "min_distance_from_world_origin": 1000
  }
}

Structures with Exclusion

For structures that avoid other structures:

{
  "placement": {
    "spacing": 30,
    "separation": 25,
    "super_exclusion_zone": {
      "chunk_count": 5,
      "other_set": "#namespace:avoid_tag"
    }
  }
}

Structure Set Tags

You can create tags that group structure sets together. Useful for exclusion zones:

File: data/mvs/tags/worldgen/structure_set/common_avoid.json

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

Then reference it in exclusion zones:

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

Troubleshooting

Structures not spawning?

• Check spacing > separation (must be true!)
• Verify structure JSON exists and is valid
• Check biome tags/biomes in structure JSON
• Ensure structure set JSON syntax is correct

Structures too common/rare?

• Adjust spacing (higher = rarer)
• Adjust separation (affects minimum distance)
• Remember the 1.65x multiplier!

Structures spawning too close together?

• Increase separation value
• Use exclusion zones
• Check other structure sets aren't conflicting

Exclusion zones not working?

• Verify structure set tags exist
• Check tag syntax is correct
• Ensure chunk_count is appropriate
• Verify referenced structure sets exist

Best Practices

1. Unique Salts - Each structure set should have a unique salt value
2. Appropriate Spacing - Match spacing to structure rarity
3. Exclusion Zones - Use them to prevent structure overlap
4. Structure Set Tags - Group related structures for easier management
5. Testing - Test structure spawning in new worlds to verify placement

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Next: Learn about Placement Systems for advanced placement options!