Worldgen (biomes, topology, and cliffs)

Worldgen is the step that turns your terrain into an actual Rust world. Up to this point you have a shape: hills, coastlines, mountains. Worldgen reads that finished shape and works out what every part of it is, the way Rust does: where the deserts and the snow belong, which slopes are cliffs, where forests grow, where the beaches start, and which water is ocean and which is a lake.

You get to it from the Worldgen button in the toolbar, or by pressing 9.

Here is the same map with worldgen off, and then generated. Nothing about the terrain changed. Only the world laid on top of it did:

What worldgen actually generates

Four layers, all derived from the terrain you already made:

• Biomes: the climate regions. Arid, Temperate, Tundra, Arctic and Jungle.
• Topology: the per-area terrain types Rust uses to decide what each patch of ground is (beach, cliff, forest, mountain, lake, and more).
• The world ground texture: a whole-map splat coat, tinted by the biome it sits in, so grass reads green in Temperate and dry in Arid.
• Lakes: land-locked water, given its own water body and its own shoreline.

Ticking Generate cliffs adds a fifth: Rust’s real cliff and rock models, placed on the steep ground.

All of it rides into the .map file you export, so RustEdit opens a finished world rather than a bare heightmap.

Generating the world

Open the panel and click Generate full map. The button becomes Regenerate map once a world exists, and the status line next to it reads Not generated, Deriving… or Generated, along with how many islands the map has.

The panel is non-modal, so the map stays live while it is open. You can generate, look, tweak a slider, and look again without closing anything. Press 9 again or Escape to close it.

Two more buttons sit on that row:

• Reset puts every worldgen value back to its default.
• Clear throws the generated world away and returns the map to bare terrain. It only becomes available once a world exists.

Auto-generate on conjure

Off by default. A conjure gives you terrain only, and you generate the world when the shape is finished. That is deliberate: worldgen is derived from the terrain, so there is little point deriving it against a shape you are still changing.

Tick Auto-generate on conjure and every new map arrives with its world already built.

Once a map is generated, Crucible keeps the world in step with your edits on its own. Move an island and drop it, release a slider, and the layers re-derive against the new shape. You do not have to press Regenerate after every change.

Salt and the world

The Salt reroll (H) is how you roll a different world without touching your terrain.

• Salt rerolls layers only (keep terrain) is on by default, so a salt reroll leaves your shape exactly as it is and only re-rolls the world on top.
• Salt rerolls: Biomes / Tiers / Topology decide which parts move. All three are on by default. Turn one off to lock that layer while you roll the others.

This is the fastest way to audition worlds. Get the landmass you want, then hit H until the climate falls where you like it.

Biomes

The biome tab sets the climate regions. Tick Show biome overlay on the terrain to paint them onto the map so you can see exactly where each one lands:

The five Rust biomes:

• Arid: hot, dry desert. Sandy and sparse.
• Temperate: the classic green Rust look, and the biome everything else borders against.
• Tundra: the cold, muted band that sits between temperate land and the arctic.
• Arctic: snow. This is what gives ground, trees and rocks their snowed-over look.
• Jungle: dense, humid, heavily forested.

Each row has a checkbox (allow this biome at all), a colour swatch, and a share slider with a live percentage.

The thing worth understanding: until you touch a slider, the sliders mirror what the salt rolled, so they move on every reroll and show you the mix you actually got. The moment you grab one, that becomes a target you have set, and Crucible holds the percentages there while salt rerolls keep relocating the biomes. Reset hands control back to the salt.

Biomes are placed from the terrain, not sprayed at random, so an arctic region settles on the cold end of the map and a desert lands on the dry flank. Regions finger into each other along the shape of the ground instead of meeting on a straight line.

If you want to overrule the result anywhere, use the biome brush.

Topology

Topology is Rust’s per-area terrain-type layer. It tags every part of the map as beach, cliff, forest, mountain, lake and so on, and Rust reads those tags to decide how each patch of ground behaves: where a shoreline is, which slopes get decorated as real cliffs, where forests and ore nodes belong, and how spawns and monuments treat the ground.

Unlike a ground texture, a single spot can carry several topology tags at once, so topology is a set of on/off layers rather than one colour.

The topology tab lists all 22 layers:

Ocean · Oceanside · Offshore · Beach · Beachside · Cliff · Cliffside · Decor · Clutter · Field · Forest · Forestside · Alt · Summit · Mountain · Hilltop · Lake · Lakeside · Tier0 · Tier1 · Tier2 · Mainland

Every row is two controls, and this catches people out:

• The row itself toggles that layer’s overlay on the map, so you can see where it sits. The tooltip reads “Click to show this layer”.
• The checkbox inside the row decides whether that layer gets generated at all. The tooltip reads “Generate this topology layer”.

So clicking the word Cliff shows you the cliffs. Clicking the box next to it stops them being generated. The Gen: all / none and Show: all / none buttons at the top of the list do both in bulk.

Leave the generate boxes alone unless you have a specific reason. The defaults produce a correct Rust world.

Tiers

Tier 0, Tier 1 and Tier 2 are Rust’s difficulty bands, and they drive what spawns where. The three sliders are constant-sum: drag one and the other two rescale so they always total 100%. Dragging a tier shows only the tier overlays and re-derives live, so you can see the bands move as you set them.

Rotation turns the tier bands across the map. Tick Auto (salt) to let each salt reroll turn them for you.

The world ground texture

The splat tab has a single option: Generate the world splat layer, on by default.

With it on, generating classifies a ground texture across the whole map from the settled terrain: seabed sand, shorelines, rock on the cliffs, snow caps, forest stands and grass, all tinted by the biome underneath. This is what makes the generated map look like a Rust map rather than a green blob.

Turn it off and the map keeps its simpler per-island base surface, while biomes and topology still derive normally.

This world texture is separate from anything you paint by hand with the splat brush. When you export, your hand painting is merged over the top of it, so you get the generated world with your own work laid on it.

Lakes

Any land-locked body of water big enough to count becomes a lake: it gets the Lake topology, its own shoreline ring, a gravel and stone bed, and a real Rust water body so it renders as an actual lake in game rather than a hole full of sea.

Lakes get their own colour in the in-game view so you can pick them out at a glance, and lake shores grow their own forest edges and, where the ground suits it, their own cliffs.

Cliffs

Generate cliffs places Rust’s real cliff and rock models on the steep ground: tall cliff walls on the sheer faces, hill cliffs and scattered rock on the softer slopes. They are baked into your .map, so they are there when the map opens in RustEdit and when players load in.

It is off by default, because standing up thousands of real models is heavy.

When cliffs are on, the in-game view becomes view-only. You can fly the camera and look, but the terrain brush, conjure, salt and the grid are locked there, because any of those would rewrite the terrain and respawn every cliff. Switch to the 3D view to keep editing. Splat painting still works in the in-game view with cliffs on.

You do not have to turn this on to ship cliffs. The MAP File + Cliffs export generates them at export time either way, so you can keep the viewer light and still export a cliffed map. See export a Rust .map file.

What ends up in the .map

Everything on this page. When you export a MAP File + Cliffs (the default output), the file carries your terrain, the biomes, all the topology layers, the world ground texture, the lakes as real water bodies, and the cliff and rock models. RustEdit opens it as a finished world.

A map you never generated still exports correctly. It simply ships as fully Temperate, with terrain and ground textures and no derived world.

Tips

• Get the terrain finished first, then generate. Worldgen reads the shape, so it is the last step, not the first.
• Use H (salt) to audition climates without losing the landmass you like.
• Turn the biome overlay on while you set shares. The percentages are much easier to judge when you can see where they land.
• Leave Generate cliffs off while you are shaping, and turn it on when you want to look at the finished thing.
• Reach for the biome and topology brushes only where the generated result is not what you want. The derive gets most maps right on its own.