feat(biome): Milestone 1 — Biome Foundation + Terrain Shape Variation

[maxfelker]

Milestone 1: Biome Configuration Foundation + Terrain Shape Variation

Overview

Adds the core biome system to the terrain generation engine. Each region of the world now has a distinct biome (Grassland, Desert, Mountains, Valley, Swamp, or Forest), each generating visually different terrain shapes.

How Biome Selection Works

Two low-frequency noise maps (temperature + humidity) are sampled at each chunk center with domain warping to create organic, curved biome boundaries (no grid lines). The temperature × humidity pair maps to a biome via a simplified Whittaker biome classification chart, which naturally enforces valid adjacency — desert and swamp are never neighbors.

Biome Terrain Parameters

Biome	Octaves	Frequency	Persistence	Height Mult	Effect
Grassland	5	0.0008	0.50	1.0×	Gentle rolling hills
Desert	3	0.0004	0.40	0.8×	Long smooth dunes
Mountains	7	0.002	0.60	3.0×	Steep jagged peaks
Valley	4	0.0006	0.45	0.6×	Wide, gentle lowlands
Swamp	2	0.001	0.35	0.25×	Nearly flat
Forest	5	0.001	0.55	1.2×	Moderate hilly terrain

Files Changed

Go WASM (new package wasm/biome/):

• biome.go — BiomeType, BiomeDefinition structs
• registry.go — 6 biome configs + ScaleHeightmap helper
• selector.go — Domain-warped temperature/humidity noise → Whittaker classification
• world_config.go — WorldConfig (seed, biomeScale)
• biome_test.go — 9 tests covering determinism, Whittaker rules, registry completeness

Go WASM (modified wasm/main.go):

• goGenerateChunk: applies biome noise params, scales heightmap and extended heightmap, returns biomeId appended to combined buffer
• goLoadWorldConfig: new WASM export for loading WorldConfig JSON

TypeScript:

• src/engine/biome/BiomeTypes.ts — BiomeType const object, WorldConfig type
• src/engine/biome/BiomeRegistry.ts — client-side biome metadata
• WasmBridge.ts — updated global declarations
• terrain.worker.ts — decodes biomeId from combined buffer, handles loadWorldConfig
• WasmClient.ts — generateChunk returns biomeId; adds loadWorldConfig()
• ChunkManager.ts — ChunkGPUData stores biomeId

Test Results

• ✅ All Go tests pass (go test ./...)
• ✅ All 56 TypeScript tests pass (npm test)
• ✅ Docker prod build passes and serves 200 OK

Visual Result

Walking in the world now encounters dramatically different terrain shapes: flat swamp regions, towering jagged mountains (3× standard height), smooth desert dunes, and moderate rolling forest terrain.