Open Terrain Generator Mod — Reference

Custom Objects & Structures (BO3/BO4)

OTG uses Biome Objects (BO) to place everything from a single tree to a sprawling city.

BO3 vs BO4

• BO3 (1.12.2+): The standard format for custom objects. Supports NBT data, mob spawners, and branching.
• BO4 (1.16.5+): An optimized format designed for massive structures. It handles branching more efficiently and is required for complex procedural generation in newer versions.

Structure Mechanics

Objects are placed via the Resource Queue in the BiomeConfig using the CustomObject or CustomStructure tags.

• Branching: A BO3 can have "branches" that point to other BO3s. This allows the engine to "build" a village by starting with a path and branching out into houses, wells, and towers.
• Block Checks: Objects can be set to only spawn if certain conditions are met (e.g., "only spawn on Grass" or "only spawn if there is Air above").
• NBT Support: Chests in custom structures can be assigned specific loot tables, and spawners can be configured for any entity.

Mob Spawning & Entities

OTG does not add new mob entities but provides granular control over where vanilla and modded mobs appear. This is configured in the BiomeConfig under the MobSpawning section.

Spawning Parameters

For each mob type (Monster, Creature, Ambient, Water), you can define: * Mob Name: The internal ID (e.g., minecraft:zombie or pixelmon:pikachu). * Weight: The probability of this mob spawning relative to others. * Count: The minimum and maximum group size.

Custom Entity Tags

Within BO3/BO4 objects, you can use the Entity tag to place specific mobs at fixed locations. These entities can include NBT data for equipment, health, and custom names.