Bounded Not Free

Bounded Not Free is a NeoForge 1.21.1 world-generation mod for modpacks that want more control over where biomes and structures appear without replacing Minecraft's terrain generation.

It lets you create a finite, shaped world with guaranteed biomes, controlled structure placement, distinct world edges, large geographic regions, and optional progression areas all while still allowing terrain and biome mods to do their thing.

In other words: you can design the layout of the world without having to build the world by hand.

Wiki

By default, the mod doesn't change world generation until you enable it.

World-generation settings should ideally be finalized before creating the world. Existing chunks are never regenerated when the configuration changes, so changing the layout later can create visible differences between old and new terrain.

Features

Custom World Shapes

Your playable world can use several different boundary shapes:

• Circle
• Square
• Diamond
• Hexagon
• Rounded square
• Polygon
• Star
• Organic / naturally irregular shapes

Different dimensions can have their own settings, so the Overworld, Nether, End, and modded dimensions don't have to use the same layout.

Controlled Biome Placement

Bounded Not Free can control where biomes are allowed or encouraged to generate.

You can:

• Allow or deny specific biomes.
• Target entire biome tags.
• Create your own named biome groups.
• Require certain biomes to appear somewhere in the world.
• Give biomes minimum and maximum distances from the center or edge.
• Restrict biomes to certain regions or progression zones.
• Create broad geographic layouts instead of completely random biome placement.

Available layout styles include:

• Vanilla – keeps biome placement close to normal Minecraft generation.
• Radial – organizes biomes based on distance from the center.
• Continents – encourages large continental regions.
• Voronoi – divides the world into large irregular biome territories.
• Climate Bands – creates broad climate-based regions.
• Archipelago – favors island-like biome groupings.

The mod still allows the active biome generator to make the final biome choice whenever possible, which helps it work naturally with modded biomes.

Guaranteed Biomes

You can require important biomes or biome groups to exist inside the generated world.

This is useful for smaller or limited-size worlds where normal random generation might otherwise leave out something required for progression.

For example, a pack could guarantee that the world contains:

• A desert
• A snowy region
• A jungle
• A mushroom biome
• Every biome required by a progression mod

The mod plans space for required content rather than simply hoping normal generation happens to include it.

Structure Control

Structures can be controlled in much the same way as biomes.

You can:

• Allow or deny structures.
• Use individual structures or structure tags.
• Create named structure groups.
• Restrict structures by distance.
• Restrict structures to certain regions or zones.
• Ensure important structures have suitable areas in which to generate.

This makes it much easier to create compact exploration-focused modpacks without players having to travel tens of thousands of blocks to find something important.

World Rim

The edge of the world can have its own biome or biome group.

Instead of abruptly cutting the world off, Bounded Not Free can influence normal terrain generation as players approach the edge, allowing the rim to feel like a natural part of the world.

For example, your world could be surrounded by:

• Mountains
• Ocean
• Frozen wasteland
• Desert
• A dangerous modded biome
• Any other configured biome or biome group

The transition can happen gradually rather than appearing as a hard biome line.

Outside the World

You can separately control what happens beyond the configured world boundary.

This allows the playable world shape and the terrain outside it to be treated differently.

You can also optionally create a one-block-thick barrier wall that follows the exact configured world shape from bottom to top.

Optional Gameplay Border

The actual gameplay border can follow the configured world shape rather than being limited to Minecraft's normal square world border.

This is especially useful for circular, hexagonal, star-shaped, or irregular worlds.

Regions and Progression Zones

Large portions of the world can be divided into named regions or zones.

These can be used to create things such as:

• Early-game areas
• Mid-game territories
• Dangerous outer regions
• Biome-themed continents
• Structure-specific regions
• Progression rings moving outward from spawn

Progression zones are completely optional. The mod can just as easily be used to create a compact world with controlled geography and no progression system at all.

Compatibility

Bounded Not Free is specifically designed to work alongside other world-generation mods rather than replace them.

It focuses primarily on deciding where things should appear, while the active terrain generator remains responsible for actually creating the terrain.

This makes it suitable for packs using mods such as:

• Tectonic
• Regions Unexplored
• TerraBlender-based biome mods
• Lithostitched-based worldgen mods
• Structure mods
• Datapack-added biomes and structures

The rim system also attempts to influence the active terrain generator naturally, so a mountain rim created with Tectonic should look like Tectonic terrain rather than terrain generated separately by Bounded Not Free.

C2ME

Bounded Not Free is designed to remain compatible with C2ME's threaded chunk generation.

Normal C2ME configurations can still use full terrain-aware world rims, including with Tectonic.

Some highly experimental C2ME world-generation options may prevent Bounded Not Free from safely influencing modded terrain. When that happens, the mod falls back to controlling the biomes only rather than risking broken or fragmented terrain.

Configuration

The main configuration file is:

config/boundednotfree/world-layout.json

The configuration controls things such as:

• Enabled dimensions
• World size
• World shape
• Biome rules
• Structure rules
• Required biomes and structures
• World rim
• Outside terrain
• Geographic layout style
• Regions
• Progression zones
• Barrier walls
• World-layout seed

World layouts are deterministic, meaning the same configuration and layout seed can reproduce the same overall geographic plan.

A world can also lock its generated layout so later configuration changes don't accidentally change the intended geography.

Previewing Your World

Before committing to a world, you can generate a preview of the configured layout with:

/worldlayout preview

The preview is saved inside:

<world>/boundednotfree-previews/

This makes it easier for modpack creators to check things such as:

• World shape
• Biome regions
• Required biome placement
• Progression zones
• Rim areas

without manually exploring the entire world.

Useful Commands

These commands require operator permissions.

/worldlayout info

Shows information about your current position, including the region or zone you're in and your distance from the world edge.

/worldlayout validate

Checks the configuration for missing biomes, structures, invalid rules, or required content that cannot be placed.

/worldlayout compat

Shows information about the active world generator and detected world-generation mods. This is mainly useful when troubleshooting a modpack.

/worldlayout preview

Generates a visual preview of the configured world layout.

Who Is This Mod For?

Bounded Not Free is mainly intended for modpack creators who want exploration to happen within a deliberately sized world.

It works particularly well for packs built around:

• Exploration
• Boss hunting
• Structure progression
• Adventure
• RPG-style progression
• Multiplayer worlds where players should remain relatively close together
• Curated biome progression
• Finite-world survival

You get much of the control of a custom-built adventure map while still keeping the unpredictability and replayability of procedural Minecraft world generation.