Draw a building once and let generated worlds fill themselves with it.
Structure Prefabs
Generated terrain gives you hills, rivers and forests. Structure prefabs give you the things people built on them.
A prefab is not a description of a building — it is a building. You draw a cottage on an ordinary map, exactly as you would draw any map, and mark it as a prefab. When a world is generated, copies of that map are stamped onto ground that suits it: the same tiles, the same objects, the same walls and roof, placed as you drew them. Nothing is invented, so nothing can appear that you have not made.
Where to Author It#
| What | Where |
|---|---|
| Draw the building | Maps → New Map, then paint it like any other map |
| Mark it as a prefab | Maps → right-click the map in the map tree → Structure Prefab… |
| See structures appear | Maps → open a large map → Generate Zone |
Setting One Up#
- Create a map at the size of the building. A cottage might be 6×6 tiles; a keep might be 24×24. The map's own size is the footprint, so do not leave a wide margin of empty grass around it — that margin gets stamped too, and will erase the terrain it lands on.
- Draw it. Ground tiles, walls, objects, fringe, roof. Anything a map can hold, a prefab can hold.
- Right-click the map in the map tree and choose Structure Prefab….
- Tick "Stamp this map into generated worlds", choose a Kind, and save. That is enough — a prefab with nothing else set will stand anywhere walkable.
- Add biomes if you want it restricted. A prefab with an empty biome list appears anywhere; the moment you add one biome, it appears only in the biomes you listed.
- Generate a large map. Structures are placed as part of generation, not as a separate step.
The Fields#
| Field | What it does |
|---|---|
| Stamp this map into generated worlds | Turns the prefab on and off without losing its settings. An unticked prefab is skipped entirely. |
| Kind | Building, ruin, camp, landmark, farm or bridge. Grouping only — it never changes where a prefab may stand. Choosing a kind re-suggests a sensible spacing for it, since a landmark and a shed want very different amounts of room. Choosing bridge also fills in a starting crossing rule, because a bridge without one stands in a field. |
| Ground it needs | Dry land, water, the water's edge, or anything. This is what lets a structure stand somewhere other than a field — see Water & Crossings. |
| How often it is chosen | Relative weight against the other prefabs eligible on the same ground. A cottage at 300 beside a chapel at 100 appears three times as often. Zero withdraws it from every draw without deleting it. |
| Clear tiles between structures | Measured from this footprint's edge to the next structure's. This is what turns a scatter of buildings into a landscape with breathing room. When two prefabs disagree, the larger value wins — a landmark that wants sixty tiles of isolation is never overruled by a shed that wants two. |
| Ground kept clear around it | Tiles around the footprint where nothing is scattered, so a forest cannot close over the door. |
| Most per map | A hard ceiling on copies in one generated map. Leave blank for as many as fit; set 1 for a unique landmark. |
| Fewest per map | A floor. If the ordinary sweep comes up short, generation searches again just for this prefab before giving up, and reports the shortfall if even that cannot meet it. Leave blank for no guarantee. |
| Kept back from the map's edge | Tiles. Stops half a building being cut off at the border. |
| At least / at most this far from water | Inland-only or coastal-only, without needing a beach biome to exist. A fishing hut set to at most 6 never appears in the hills. |
| Lowest / highest ground it accepts | An elevation band, 0 at sea level and 1 at the highest peak. A mountaintop shrine, a valley farm. |
| Steepest ground it will accept | How much the land under the footprint is allowed to rise and fall. A stamp cannot flatten the hill beneath it, so a building placed on ground steeper than it tolerates ends up half-buried. Flat ground only is the safe choice for anything with a foundation. |
| Biomes it may stand in | Which biomes are eligible, with a weight per biome. The weight belongs to the pair, so one fishing hut can be common on a coast and rare inland without needing two prefabs. |
Where a Structure Will Not Go#
Placement is judged against the terrain that was actually generated, not against the terrain that was intended. A site is refused when the footprint would:
- leave the map — a stamp clipped mid-wall looks broken
- not match the ground it needs — an ordinary building never straddles a shoreline or stands in a lake
- cover a cliff, even partly, whatever ground it asked for. A cliff is a hole in the map rather than a surface, and a stamp cannot regrade the land beneath it
- span more slope than the prefab tolerates
- fall outside its edge, elevation or water-distance band
- crowd a structure already placed, once spacing is taken into account
- break one of its relation rules — see Structure Relations
Gotchas#
The map's size is the footprint. Empty tiles inside the prefab map are still stamped, replacing whatever terrain they land on. Crop the map to the building.
A prefab with no biomes listed stands anywhere. That is deliberate — marking a map and doing nothing else should produce a prefab that appears. If you want it restricted, add at least one biome. Removing the last biome puts it back to "anywhere", not "nowhere".
A map is never its own prefab. Marking the map you are generating has no effect on that map.
Structures land the first time a chunk is generated. Like scattered objects, they are not re-stamped over an already-generated chunk — that is what protects your hand-placed edits from being overwritten. To re-place structures on a map you have already generated, tick Also erase my placed content when generating.
A prefab whose map was never painted stamps nothing. Generation reports it rather than leaving a silent hole.
Nothing appeared? The generation log names the rule that refused, per prefab. A line reads like "Stone Bridge (E–W): 0 placed — refused by span=214 spacing=6", which is the difference between tuning a number and guessing. A prefab no site was even found for says so too, rather than going unmentioned. An all-water map and a map of cliffs both end up empty, and the log is what tells them apart.
Guarantees are reported when they fail. A prefab set to at least 3 that only fits twice says so in the log rather than quietly placing two.
Studio or Enterprise tier. Like the rest of map generation, prefabs are gated in the browser editor. The desktop app behaves as full-tier.