Tree generation

common/worldgen/overworld.ts

@@ -3,6 +3,7 @@
 import { CHUNK_AREA, CHUNK_HEIGHT, CHUNK_SIZE, SEA_LEVEL } from "$/common/constants.ts";
 import { OctaveNoise2D } from "./noise.ts";
 import { OverworldTerrain, TerrainColumn } from "./terrain.ts";
+import { BIOME_TREES, grow_tree, tree_sites } from "./trees.ts";
 
 // density is sampled every CELL_WIDTH blocks across and CELL_HEIGHT up, caves every CAVE_CELL_HEIGHT up since
 // tunnels are thinner than terrain features
@@ -28,6 +29,8 @@ export interface OverworldBlocks {
 	sand: number;
 	snow: number;
 	water: number;
+	log: number;
+	leaves: number;
 }
 
 type Palette = "stone" | "dirt" | "grass" | "sand" | "snow";
@@ -183,7 +186,8 @@ function generators_for(seed: string): SeedGenerators {
 	return found;
 }
 
-// fills blocks (indexed y * CHUNK_AREA + z * CHUNK_SIZE + x) and each column's surface height and biome
+// fills blocks (indexed y * CHUNK_AREA + z * CHUNK_SIZE + x) and each column's surface height and biome.
+// blocks trees put in other chunks go to spill
 export function generate_overworld(
 	blocks: Uint32Array,
 	heights: Int32Array,
@@ -192,6 +196,7 @@ export function generate_overworld(
 	chunk_z: number,
 	seed: string,
 	ids: OverworldBlocks,
+	spill: (x: number, y: number, z: number, block: number) => void,
 ) {
 	const { terrain, snow_line, strata } = generators_for(seed);
 	const x0 = chunk_x * CHUNK_SIZE;
@@ -236,6 +241,40 @@ export function generate_overworld(
 			fill_column(x, z);
 		}
 	}
+	grow_trees();
+
+	function grow_trees() {
+		const place = (x: number, y: number, z: number, block: "log" | "leaves") => {
+			if (y < 0 || y >= CHUNK_HEIGHT) return;
+			const lx = x - x0;
+			const lz = z - z0;
+			if (lx < 0 || lx >= CHUNK_SIZE || lz < 0 || lz >= CHUNK_SIZE) {
+				// the other chunk only takes it where it has air
+				spill(x, y, z, ids[block]);
+				return;
+			}
+			const i = y * CHUNK_AREA + lz * CHUNK_SIZE + lx;
+			const current = blocks[i];
+			if (current === 0 || (block === "log" && current === ids.leaves)) {
+				blocks[i] = ids[block];
+			}
+		};
+
+		for (const site of tree_sites(seed, chunk_x, chunk_z)) {
+			const column = (site.z - z0) * CHUNK_SIZE + (site.x - x0);
+			const trees = BIOME_TREES[biomes[column]];
+			if (!trees || site.rng.next() >= trees.chance) continue;
+
+			// on soil with air above it, so never under water or on bare rock
+			const ground_y = heights[column];
+			const ground = blocks[ground_y * CHUNK_AREA + column];
+			const above = blocks[(ground_y + 1) * CHUNK_AREA + column];
+			if ((ground !== ids.grass && ground !== ids.dirt && ground !== ids.snow) || above !== 0) continue;
+
+			const kind = trees.kinds[Math.floor(site.rng.next() * trees.kinds.length)];
+			grow_tree(kind, site.x, ground_y + 1, site.z, site.rng, place);
+		}
+	}
 
 	function fill_column(x: number, z: number) {
 		const cell_x = Math.min(Math.floor(x / CELL_WIDTH), CORNERS - 2);