Spawn Tweaker

Spawn Tweaker is a Forge 1.12.2 mod allowing you to change the spawn weight and minimum/maximum group size for any modded mobs classifying as monsters in any biomes without needing to deal with tons of different mod configuration files.

In-Game Commands

• /spawntweaker import

  • Reloads the spawn configuration from the spawn_tweaker directory.
  • Use this after editing your spawn configuration to apply changes without restarting the game.
  • Note: On Minecraft startup, the mod will automatically import spawn data if either monster_spawns.yml or monster_spawns.json exists (YAML is tried first).

• /spawntweaker export <glob> [<glob> ...]

  • Exports current spawn data for entities matching the provided glob patterns to both spawn_tweaker/monster_spawns_export.yml and spawn_tweaker/monster_spawns_export.json.
  • Examples:
  • /spawntweaker export * - Exports spawn data for ALL registered monster entities.
  • /spawntweaker export mod1:* - Exports only monsters from the mod mod1.
  • /spawntweaker export thermalfoundation:* enderzoo:enderminy - Exports Thermal Foundation mobs and the specific Enderminy entity.
  • You should use the exported spawn data as a starting point to decide what to write for your configuration.

Configuration Files

Spawn Tweaker supports both YAML (.yml) and JSON (.json) formats. YAML is recommended for its readability.

File Location

Configuration files are located in the spawn_tweaker folder in your game directory:

• monster_spawns.yml (preferred) or monster_spawns.json

YAML Format (Recommended)

Please remember that in YAML leading whitespace is significant. Do not report parse errors as issues.

Structure:

# Rule 1
- for:
    entities:
      - modid:entity_name
      - modX:* # Matches all entities in modX
    biomes:
      - minecraft:plains
      - biomesoplenty:* # Matches all biomes in biomesoplenty
  spawn:
    weight: 100
    minGroupSize: 4
    maxGroupSize: 4

# Rule 2
- for:
    entities:
      - another_mod:creature
    biomes:
      - '*' # Matches ALL biomes registered to Forge
  spawn:
    weight: 50
    minGroupSize: 1
    maxGroupSize: 3

JSON Format (Also Supported)

Structure:

[
  {
    "for": {
      "entities": [
        "modid:entity_name",
        "modX:*"
      ],
      "biomes": [
        "minecraft:plains",
        "biomesoplenty:*"
      ]
    },
    "spawn": {
      "weight": 100,
      "minGroupSize": 4,
      "maxGroupSize": 4
    }
  }
]

Configuration Fields

Each rule consists of two sections:

for Section

• entities: List of entity registry names or glob patterns (e.g., minecraft:zombie, mymod:*)
• biomes: List of biome registry names or glob patterns (e.g., minecraft:plains, biomesoplenty:*, * for all biomes)

spawn Section

• weight: The spawn weight. Higher numbers mean the entity spawns more frequently.
• minGroupSize: The minimum number of entities that spawn in a group.
• maxGroupSize: The maximum number of entities that spawn in a group.

Example Configuration

Here's a YAML example that sets all Five Nights at Freddycraft entities to spawn with low frequency in all biomes:

- for:
    entities:
      - five_nights_at_freddycraft:*
    biomes:
      - '*'
  spawn:
    weight: 1
    minGroupSize: 1
    maxGroupSize: 1

This configuration should yield output similar to the following in your logs upon startup:

[Client thread/INFO] [dev.trustytrojan.spawn_tweaker.SpawnTweaker]: Importing monster spawn data...
[Client thread/INFO] [dev.trustytrojan.spawn_tweaker.YamlHandler]: Loaded 1 spawn rules from YAML: monster_spawns.yml
[Client thread/INFO] [dev.trustytrojan.spawn_tweaker.SpawnTweaker]: Rule #1 applied for 62 entities in 1 biomes
[Client thread/INFO] [dev.trustytrojan.spawn_tweaker.SpawnTweaker]: Monster spawn data imported successfully

Notes

• Pattern Matching: Both entity and biome fields support glob patterns using * (matches any characters) and ? (matches single character).
• Multiple Rules: You can define multiple rules to configure different entities & biomes with different spawn settings.
• Auto-Detection: On import, the mod tries YAML first (.yml), then falls back to JSON (.json).
• Export: The export command generates both YAML and JSON files for your convenience.
• Validation: If a pattern matches no entities or no biomes, the entry is skipped and a warning is logged.