Clear the canvas?
This wipes your painted terrain to a blank ocean. There's no undo.
Paint a landmass and a GPU erosion filter carves realistic gullies, ridges, and drainage networks into it in real time — built for making terrain heightmaps and topographic wallpapers.
Hit Paint in the top switch and drag on the map to raise land (hold Shift or right-drag to lower, or set the brush to Smooth to even out rough spots). Switch to 3D View to orbit the rendered landscape by dragging. Tune the Erosion and Gully Shape sliders, or try a Preset, to restyle the carving live. The Layer chips switch between relief, height, slope, surface normals, ridges, and drainage. Bring in your own shape from the Import Shape panel — a filled outline becomes a landmass boundary that terrain auto-generates inside (great for mapping a D&D world), or a grayscale heightmap loads as terrain directly. Export a 4K wallpaper, a 16-bit heightmap, or a 3D-printable STL — or record a 360° turn as an MP4 from the View panel.
Erosion-filter technique by Rune Skovbo Johansen, building on work by Clay John and Fewes. Shader released under MPL-2.0.
Gullywash is a free, browser-based terrain painter and heightmap generator. You paint a landmass and a GPU erosion filter carves realistic gullies, ridges, and drainage networks into it in real time. No account, no download, no signup.
Hit Paint, drag to shape your landmass, let the erosion settle, then open the panel and click Heightmap 16-bit. You get a grayscale PNG you can import as terrain in any engine.
A 16-bit grayscale PNG at 1024×1024, following the standard convention: white is the highest ground, black is the lowest. The wallpaper export is a 4K (3840×2160) full-color landscape render of your island in the ocean.
In Unreal, use Landscape › Import from File and pick the PNG. In Unity, import it as a raw/PNG heightmap on a Terrain. In Godot, feed it to a HeightMapShape3D or a displacement material. In Blender, drop it into a Displace modifier or a displacement node. Cities: Skylines also takes 16-bit grayscale heightmaps. If an engine wants a specific size, resample the PNG first.
An 8-bit heightmap only has 256 height levels, which shows up as visible steps or "terracing" on smooth slopes. 16-bit gives you 65,536 levels, so gentle gradients stay smooth. Most engines accept 16-bit, so it's worth using.
Yes. Choose STL in the Output panel and click Generate STL to download a watertight solid relief tile — a 120 mm square with your terrain raised on top — ready to slice in Bambu Studio, Cura, or PrusaSlicer.
Yes. In the View panel, set the turn length and video size, then click Record a Turn to capture one full 360° rotation. It downloads as an MP4 (or WebM in Firefox) that plays in standard players and editors. Keep the tab in front while it records so the video stays smooth.
Yes — that's the whole point. Most free generators only give you noise or real-world data. In Gullywash you paint the landmass by hand in Paint mode (drag to raise, Shift or right-drag to lower), and the erosion filter does the realistic carving on top of your shape.
World Machine and Gaea are powerful paid desktop apps with deep node graphs and a learning curve. Gullywash is free, runs in a browser tab, and trades depth for speed: paint, carve, export in under a minute. Great for prototyping, jam games, and quick wallpapers rather than AAA final terrain.
No. Everything runs on your own device's GPU. Nothing is uploaded, stored, or sent to a server — exports download straight to your computer. If your browser supports WebGL2 with floating-point render targets, you're good to go.
Yes. In Import Shape, choose Boundary and load a filled silhouette or transparent PNG of your landmass — terrain auto-generates inside that outline, so you can detail a continent or a floating D&D island within a coastline you already drew. Turn on Lock painting and land can't be brushed past the shape, so even a skull icon stays skull-shaped. Hit Vary Terrain to re-roll what's inside, or Invert if the wrong half came in as land. Or choose Heightmap to load a grayscale image as the terrain directly, then let erosion carve it.
Tune the Erosion and Gully Shape sliders, hit Randomize, or pick a preset like Alpine, Canyon, Badlands, Mesa, Rolling Hills, or Continent. For a softer, gentler landscape generator, try Rolling Hills.
This terrain painter needs WebGL2 with floating-point render targets — the eroded heightmap is computed in full-precision GPU buffers.
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Erosion-filter technique by Rune Skovbo Johansen, after Clay John & Fewes (MPL-2.0).