Channels, cut water through your map

A channel is open water cut clean across the map. It is not a bay: it runs from one edge to the other and severs every landmass in its path, so one cut turns a continent into two islands with a real strait between them. Every cut is aimed through your land, so even on a small island each one makes a strait. An inlet is the other kind of cut: it runs in from the open sea and stops inland, for a fjord or a harbour.

That makes Channels the fastest way to add water to a map you already like. The land, the mountains and the coastline you rolled stay exactly where they are, and the water is cut through them.

Open the tool

Channels is its own tool, the square button to the right of the brush buttons in the toolbar. Click it, or press L.

A small dock opens over the map, the same way the brush docks do. Opening Channels closes whichever brush was open, and pressing Escape closes it again.

The dock

Every one of these starts at nothing, so a map only gets channels when you ask for them.

• Cuts (0 to 16): how many channels cross the map. Because a cut is global, the count means the same thing on a one-island map and a thirty-island one. Start at 1 or 2 for a map split into a few big pieces, go higher for a broken, waterway-heavy world.
• Inlets (0 to 12): how many inlets are cut into the coast. Each opens about 200 to 280 m wide at the sea and narrows toward its head inland, which is room for a harbour or a fishing village at the mouth.
• Variant (0 to 1): slides the cuts and inlets to a different layout without touching your seed, the same way Shape variant rerolls an outline. Use it when you like the map but not where the water runs.
• Width: how wide the rolled cuts are, shown in metres of open water. The widest player boat is 18 m across, so 36 m or more takes any boat with room to steer; on a small map the bottom of the slider goes narrower than that, and the readout turns amber when it does.
• Width random (0 to 1, default 0): spreads the widths apart. At 0 every cut is the same size, and at 1 some cuts are creeks while others open into wide straits.
• Edge variation (0 to 1, default 1): how ragged the banks are. At 0 a cut has two straight sides. The default gives it bays, headlands and peninsulas along its length, so it reads as a natural waterway rather than a canal.
• Depth (2 to 30 m, default Sea): how deep the water in the cuts gets. At the top it is as deep as the open sea. Water bases only place in 2 to 4 m of water, and 12 m or less stays in reach of a bridge pier in Crucible Creator.

Draw your own channels

Draw cuts opens a pad showing your map in the colours of an exported map, and you draw the water on it by hand. The same dock rows sit beside the pad, so you can roll cuts and draw them without closing anything.

With the Draw tool (1):

• Left-drag cuts a channel. It follows your line, with the same banks and the same edge variation a rolled cut gets. Hold Shift for a straight line.
• Right-drag puts the land back. It is an eraser for the channels you painted, so it only ever removes water you added, and it cannot invent land that was never there.
• The ring on the cursor is the width the next stroke will be.

Draw width sets that width in metres, from 20 up to 600, so it means the same thing whatever size your map is. [ and ] nudge it while you draw. Smoothing rounds the line you draw next, so a shaky hand still makes a smooth channel.

The pad opens with Preview on: the real map with your cuts in it, banks and shallows included. Turn it off to draw over the plain map, where drawn cuts show in channel blue with a light outline. The wheel zooms up to 6x, Space-drag or middle-drag pans, and 0 goes back to the whole map.

Edit a cut you drew

The Pick tool (2) works on cuts you already drew. Click a cut to pick it. Ctrl + click picks more cuts or drops one, and Shift + click picks every cut in the list from the first pick to that one. Then:

• Drag it to move it, or nudge it with the arrow keys. With several picked, they all move together.
• Change its Cut width and Smoothing; with several picked, every one takes the new value. Smoothing always starts from the line as you drew it, so 0 puts the original back.
• Taper narrows it toward the end you finished drawing it at, for a fjord running to a head, or below 0 widens it toward that end, for a bay opening to the sea. Its average width stays the same. The row is always there and greys out while nothing is picked.
• Delete removes it, or every picked cut.
• Merge, at the bottom of the panel under the cut list, makes the picked cuts one cut exactly as they are: each keeps its own shape, place, width, smoothing and taper. From then on they show as one row and pick, move, delete and take slider changes together. Cuts and land you put back are never merged together.

The pad also lists every drawn cut, filling the space under the controls before it scrolls. Hover a row to see the cut on the map, click it to pick it; Ctrl and Shift work there too.

A cut that never reaches the open sea is flagged in that list. Rust only counts low water as ocean where it joins the map’s edge, so a cut sealed off from the sea ships as an enclosed pool, not a channel. The extend button beside its width carries its nearer end straight on until it meets open sea.

Keep a rolled cut

Pick a rolled cut and the pad offers Keep this cut (K). It turns that cut into one of your drawn cuts, on the same path and width: from then on it is yours to move, resize, taper and delete, Variant and Conjure stop moving it, and Cuts drops by one.

Undo, apply, cancel

Undo and redo cover every stroke, move, resize, delete, merge, clear and keep. Apply cuts what you drew into the real map and closes the pad, and you can reopen it later and keep editing the same cuts. Cancel closes the pad and puts everything back how it was, sliders included. Escape drops a pick first; with nothing picked it closes the pad, asking first if you changed anything.

The pad’s keys are listed in keyboard shortcuts, and you can rebind them in Settings, Keybinds.

Drawn and rolled cuts live together

Anything you draw is added to the cuts the sliders roll, never instead of them. You can roll two straits, then hand-draw the one creek you actually wanted in the north. Width random and Variant give your drawn cuts their own random width too, never a different path. The rolled Width leaves them alone.

Your drawn strokes and the channel settings are part of the map, so they survive a conjure or a salt reroll: the land re-rolls underneath and your channels stay where you put them. The bin beside Draw cuts discards the hand-drawn ones and leaves the rolled ones alone.

Make a cut belong to its island

A drawn cut normally sits on the map, not on the land it crosses, so moving an island afterwards slides it out from under its own channel. Bake into islands fixes that: each stroke is handed to the island it cuts, and from then on the cut moves, turns and resizes with that island. Nothing about the terrain changes when you bake.

Inlets belong to their island from the start, so they move with it too. With an island selected, the dock lists its baked cuts and inlets, each with a button to remove it and bring the land back.

Rolled cuts stay on the map by design, since they are a property of the map rather than of any one island. They re-aim through your land whenever it changes, so moving or resizing an island moves them with it; Keep a cut to pin it in place.

What a channel does to the rest of the map

Channels change the terrain itself, not just the picture. That means they carry into everything downstream with no extra work:

• The exported .map file and the RAW heightmap.
• The in-game view, where you can fly the strait and see the scale of it.
• The worldgen: the water in a cut that reaches the sea is real ocean, with the Ocean and Oceanside topology layers to match, so Rust treats it as sea and not as a hole in the ground.

Tips

• 20 m is the narrowest drawn cut that still opens water. A second pass over the same line widens it.
• Draw the line you want and leave the raggedness to Edge variation. Trying to draw the wobble by hand fights the bank noise that is already there.
• For a harbour, raise Inlets rather than drawing one: an inlet starts at open sea by construction, so it never ends up as an enclosed pool.
• If you want water between separate landmasses rather than through one, full multi-island maps roll that shape from the start, and Channels still works on top of it.

Next steps

• Generate the world so the new shorelines get their biomes, splats and topology.
• Export your map and open it in RustEdit.