"Procedural generation in games: where the scatter has to stop"

Development covered 16 Sep 2026 to 18 Sep 2026 (commit dates).

Two kinds of thing make up the overworld of Myriad Immortal Sect. There are authored places, the sect compounds, the city, the landmarks, laid out by hand. And there is wilderness, filled in by a generator that scatters trees, rocks, herbs, ore veins and beasts according to the biome. Both are necessary. A world drawn entirely by hand would be tiny, and one drawn entirely by rules would have nowhere worth arriving at.

This week was about the seam between them. Every problem I found lived exactly where one kind of content leaked into the other, and each one turned into a rule I want to keep for procedural generation in games.

246 herbs on a plaza

Standing at the centre of Medicine King Valley, a disciple of that sect had 273 interactable things loaded inside the dome. After the fix, 27.

The generator had been told to keep clear of the player's home compound, and it did. It had not been told about the other three sects' compounds, so their paved plazas were carpeted with wild herb patches, ore veins and beast ranges. On the plaza of a valley famous for cultivating herbs properly in its gardens, the ground was covered in random roadside herbs. It read as a meadow with buildings standing in it.

The rule now is that procedural scatter never enters any sect's dome. Authored spawn zones inside a compound still work, because they were placed on purpose. The test is whether a person decided this belongs here; whether it is the player's home never enters into it.

If you are wondering what each compound is meant to feel like, the site's write-up of the herb-growing valley sect describes the place the scatter was trampling.

The approach belongs to the place too

The second leak was subtler. The generator's exclusion zone around a compound stopped well inside its dome, so wilderness scatter grew right up the road to each gate. A gate you walk towards through a thicket reads as abandoned.

The approach is part of the arrival. That stretch of road is now kept clear as well, so the last few dozen tiles before a gate are composed rather than generated. It is a small strip of map and it changes the first impression of every sect.

Generators pick the wrong art in plausible ways

Some of the scatter was wrong in a way no rule about location would catch. The foothill outcrops in one biome were being drawn using a frame meant for a wet pebble 38 pixels across, scaled up into a hill. At a distance it read as a rock. Up close it was a blurry stretched stone, repeated across the landscape.

I ended up writing a small survey tool that ranks every piece of art by how many times it is placed multiplied by how much it is magnified. A blurry asset placed once is a curiosity. A blurry asset placed four hundred times at triple size is what the player's eye spends the whole session on. That ranking is now how I decide what to redraw first.

Hand edits have to survive the next run

On the authored side the lesson was the reverse: the generator must never undo a person's decision. One sect's centrepiece was a hand edit that the zone tool would quietly put back on its next run, because the tool had its own idea of where that sect's gate was. The working rule is that anything a person moves is recorded as authored, and the generator treats authored items as fixed points it builds around.

A related surprise: swapping one frame for another of the same height still changed the footprint width, because the width comes from the art. "Same size" in a layout tool is not the same as "same shape on the ground", and a borrowed pond in Black Iron Valley's desert became an oasis with palms and shore stones once someone looked at what it actually was. For a wider view of how the land fits together, the map of the Mortal World shows the regions the generator fills between the authored places.

A rule worth stealing

The one line I would hand to anyone else working on procedural generation in games is a rule about intent: generated content fills space nobody chose, and authored content is space somebody did. Then make every tool respect it in both directions. Most of my map bugs this month were one side forgetting that the other existed.

The compounds are clear of weeds now: walk through one free in your browser.