Tree generation

MODS.md

@@ -714,7 +714,7 @@ produce identical terrain. So worldgen scripts must be **deterministic**.
 
 Each chunk is generated in three passes:
 
-1. **Terrain.** One terrain generator fills in the ground and water.
+1. **Terrain.** One terrain generator fills in the ground, water and trees.
 2. **Ores.** Every mod's `worldgen/ores.json`, in load order.
 3. **Features.** Every mod's registered features, in load order.
 
@@ -724,8 +724,9 @@ the Terralith datapack: continentalness, erosion and weirdness noises feed neste
 height, jaggedness and roughness, a 3D density around that height is sampled on a coarse grid and interpolated, and
 caves are cut out of it. On top of that come Terralith-style shapes: terraced plateaus, shattered hills, river valleys
 and gorges, jagged peaks and rare sky islands. Its biome ids (`biome_at`) are the keys of `BIOMES` in
-`common/worldgen/overworld.ts`, like `bworld:yosemite_cliffs` or `bworld:skylands`. It places no trees or other
-features yet. `deno run -A tools/worldgen_preview.ts [seed]` renders it to PNG files.
+`common/worldgen/overworld.ts`, like `bworld:yosemite_cliffs` or `bworld:skylands`. Trees
+(`common/worldgen/trees.ts`) are spread out like Poisson disk sampling, never closer than 4 blocks, and each biome sets
+how many grow and which kinds. `deno run -A tools/worldgen_preview.ts [seed]` renders it to PNG files.
 
 ### Terrain generators