How to Build Large Open Worlds in Unity: 5 World-Building Tools Compared

One of the easiest mistakes to make when you first think about building an open-world game is imagining the problem as:

How do I make one enormous map?

That sounds reasonable. It is also slightly dangerous.

The games we think of as “one huge world” are usually not treated internally as one enormous piece of terrain sitting there permanently, fully loaded, waiting for the player to walk across it.

The Reddit Question#

A beginner on r/Unity3D asked how developers build a city map like Los Santos and whether the map is made in pieces, squares or circles. The strongest reply was essentially yes: large games commonly divide maps into chunks that load dynamically around the player, then layer buildings, roads and other props on top. It also pointed out the part procedural-generation marketing can hide: enormous worlds still involve a lot of human work.

The embed above is served by Reddit. If a privacy extension blocks it, open the original discussion directly.

A Giant Terrain Is Not a Giant World#

Suppose you generate a beautiful 20 km landscape: mountains, forests, rivers, grass, valleys and a suitably dramatic ruined castle. Congratulations. You have terrain. You do not necessarily have an open-world system.

The difficult question is not simply “how big is the terrain?” It is “what is loaded right now, what can sleep, what can become cheaper, and what must still be remembered when the player comes back?”

Chunks: The Basic Trick Behind Huge Worlds#

The fundamental idea is simple: break the world into smaller regions. Those regions might be terrain tiles, mesh chunks, additive scenes, Addressable areas, grid cells or a custom representation.

A recent Unity example on Reddit uses around 30 base chunks with variation systems, seed-based routes and points of interest, plus lazy loading, chunk loading/unloading, LOD and asset-reference loading around the player. The author also confirmed that floating-point precision still required periodic world shifting.

The Floating-Point Problem#

Unity GameObject transforms use floating-point coordinates. Close to the origin, that is usually fine. As the player travels farther away, the precision available for representing tiny positional differences decreases. Eventually you can see instability in camera movement, physics, joints, particles, placement and other systems.

Unity’s own public world-building discussions have included requests around large-world precision, terrain management and floating-origin workflows. This is a separate engineering problem from simply generating more terrain.

Runtime Generation Adds Another Layer#

Then there is a different category entirely: generate the world while the game is running. Instead of storing the whole environment beforehand, the game creates or assembles areas when they are needed.

Another recent Reddit developer spent more than eight months building a runtime world-generation system with mesh-based terrain, biomes, roads, vegetation, water, weather, day/night and continuous streaming. That kind of project demonstrates why “world generator” can mean something much larger than terrain sculpting.

Visual Scale Is Also an Optimization Problem#

A huge environment is not only a coordinate and loading problem. It is a rendering problem. Far-away vegetation does not need the same geometry, shadows or simulation as vegetation two metres from the player.

The illusion of a huge world survives because distant things get cheaper. The player sees continuity. The engine sees budgets.

Five Practical World-Building Routes in Unity#

The numbering below is not a best-to-worst ranking. These tools solve different parts of the problem. Unity’s free route comes first because it is the correct baseline for understanding what commercial tools are actually saving you from doing manually.

01. Unity Terrain + Terrain Tools#

This is the route I would recommend first if you are still learning. It teaches the actual building blocks without hiding them behind a commercial workflow. The trade-off is that the higher-level open-world architecture is yours to build.

02. Gaia Pro VS#

Gaia makes sense when the goal is a conventional land-based world and speed matters. Its current Asset Store listing shows a 50% sale price of $99.50 against a regular $199 price, a 4.8 GB package, and compatibility listed for Built-in, URP and HDRP on Unity 2022.3.

03. MicroVerse Core Collection#

MicroVerse is especially attractive when iteration matters more than one-click generation. The current listing shows the Core Collection at $99.50 during the same sale, normally $199, with Built-in, URP and HDRP compatibility listed for its supported Unity version.

04. MapMagic 2 Bundle#

MapMagic is particularly interesting when procedural rules are part of the game itself. The current listing describes it as a node-based procedural and infinite map generator that can create new terrain during Play Mode, with the Bundle including Objects, Splines, Biomes/Functions and Brush modules.

05. Runtime World Generation#

Runtime World Generation is closer to a runtime framework than a traditional editor terrain tool. Its current listing shows $28.99, Unity 6000.4 as the original version, URP/HDRP compatibility and no Built-in support. That makes its scope unusually clear.

How the Five Routes Compare#

Prices above reflect public listings checked on 28 September 2026 and can change, particularly during Asset Store sales.

Which Route Fits You?#

What If the World Is Actually Round?#

Almost every route above assumes a variation of the same spatial model: the world is fundamentally flat terrain. It may be enormous, tiled, streamed or generated forever, but “up” is still globally obvious and the terrain model is conventional.

That is the problem space Worldsmith is being built around: not another way to sculpt a prettier mountain, but a framework for turning a spherical world into an actual playable game world.

The Real Answer to the Reddit Question#

So how do developers make massive open worlds? They do not simply make a gigantic mesh and hope the GPU is feeling generous. They divide the problem.

Behind all of that sits tooling. Often a ridiculous amount of tooling. A huge world is impressive because dozens of systems cooperate closely enough that the player never notices where one piece ends and another begins.

What I Would Tell a Beginner#

1. 01
   Make one good 500-metre area.

   Prove the basic world, art and gameplay first.

2. 02
   Split several areas into chunks.

   Make loading boundaries explicit before scale hides the architecture.

3. 03
   Load and unload without visible hitches.

   Streaming quality matters more than theoretical map size.

4. 04
   Scale vegetation and rendering.

   Use LOD, culling and cheaper distant representations.

5. 05
   Preserve state.

   Make unloaded areas remember changes when the player returns.

6. 06
   Then make it larger.

   A broken 1 km architecture does not become healthy at 100 km.

Otherwise you do not get a bigger open world. You get a much larger crime scene.

Sources and Further Reading#

• How Do They Make Massive Open Worlds To Play?
• Chunk-Based World Generation System
• Runtime World Generation development discussion
• Open-world environment discussion
• Gaia world-building discussion
• Unity Terrain Tools documentation
• Unity 3D World Building roadmap
• Gaia Pro VS
• MicroVerse Core Collection
• MapMagic 2 Bundle
• Runtime World Generation

Product prices and compatibility reflect the public listings checked on 28 September 2026 and may change later.