Fix fall-through (spawn on terrain after collision built) and B&W (assign sky env)

scripts/world/terrain.gd

@@ -2,27 +2,35 @@ extends Node3D
 ## Terrain generator — M0 placeholder.
 ##
 ## Builds ONE heightmap chunk from deterministic noise, so the world already
-## looks like rolling ground rather than a flat plane. This is intentionally
-## simple: a single chunk, generated at _ready(). Chunk streaming, biomes and
-## server-side determinism (see docs/ARCHITECTURE.md §4) come in later milestones.
+## looks like rolling ground rather than a flat plane. Single chunk, generated at
+## _ready(). Chunk streaming, biomes and server-side determinism (see
+## docs/ARCHITECTURE.md §4) come in later milestones.
 ##
 ## The mesh is generated in code (no asset needed) so the project runs the moment
 ## Godot opens it, with nothing to import.
+##
+## Exposes `sample_height(x, z)` so other systems (player spawn, prop placement)
+## can sit exactly on the surface instead of guessing a Y and falling through.
+
+signal ready_built   ## emitted once the mesh + collision exist
 
 @export var size: int = 128          # chunk is size x size metres
 @export var resolution: int = 96     # vertices per side (higher = smoother/heavier)
 @export var height_scale: float = 10.0
 @export var noise_seed: int = 1337
 
+var _noise: FastNoiseLite
+var built: bool = false
+
 func _ready() -> void:
 	_build()
 
 func _build() -> void:
-	var noise := FastNoiseLite.new()
-	noise.seed = noise_seed
-	noise.noise_type = FastNoiseLite.TYPE_PERLIN
-	noise.frequency = 0.012
-	noise.fractal_octaves = 4
+	_noise = FastNoiseLite.new()
+	_noise.seed = noise_seed
+	_noise.noise_type = FastNoiseLite.TYPE_PERLIN
+	_noise.frequency = 0.012
+	_noise.fractal_octaves = 4
 
 	var st := SurfaceTool.new()
 	st.begin(Mesh.PRIMITIVE_TRIANGLES)
@@ -40,21 +48,21 @@ func _build() -> void:
 			var x1 := (x + 1) * step - half
 			var z1 := (z + 1) * step - half
 
-			var p00 := Vector3(x0, _height(noise, x0, z0), z0)
-			var p10 := Vector3(x1, _height(noise, x1, z0), z0)
-			var p01 := Vector3(x0, _height(noise, x0, z1), z1)
-			var p11 := Vector3(x1, _height(noise, x1, z1), z1)
+			var p00 := Vector3(x0, sample_height(x0, z0), z0)
+			var p10 := Vector3(x1, sample_height(x1, z0), z0)
+			var p01 := Vector3(x0, sample_height(x0, z1), z1)
+			var p11 := Vector3(x1, sample_height(x1, z1), z1)
 
 			_add_tri(st, p00, p01, p11, half, uv_scale)
 			_add_tri(st, p00, p11, p10, half, uv_scale)
 
 	# Normals give the lighting its shape. Tangents are only needed for normal
-	# maps, which this low-poly material doesn't use — so we skip them (and avoid
-	# the "UVs required to generate tangents" error).
+	# maps, which this low-poly material doesn't use — so we skip them.
 	st.generate_normals()
 
 	var mesh := st.commit()
 	var mi := MeshInstance3D.new()
+	mi.name = "TerrainMesh"
 	mi.mesh = mesh
 
 	# Simple ground material. Low-poly look = flat-ish colour + lighting does the rest.
@@ -64,16 +72,28 @@ func _build() -> void:
 	mi.material_override = mat
 	add_child(mi)
 
-	# Collision so the player can walk on it.
+	# Collision so the player can walk on it. Build the body BEFORE marking built
+	# so anything spawning on ready_built already has ground under it.
 	var body := StaticBody3D.new()
+	body.name = "TerrainBody"
 	var shape := CollisionShape3D.new()
-	var col := mesh.create_trimesh_shape()
-	shape.shape = col
+	shape.shape = mesh.create_trimesh_shape()
 	body.add_child(shape)
 	add_child(body)
 
-func _height(noise: FastNoiseLite, x: float, z: float) -> float:
-	return noise.get_noise_2d(x, z) * height_scale
+	built = true
+	ready_built.emit()
+
+## World-space ground height at (x, z). Safe to call before or after _build()
+## because it lazily creates the noise object.
+func sample_height(x: float, z: float) -> float:
+	if _noise == null:
+		_noise = FastNoiseLite.new()
+		_noise.seed = noise_seed
+		_noise.noise_type = FastNoiseLite.TYPE_PERLIN
+		_noise.frequency = 0.012
+		_noise.fractal_octaves = 4
+	return _noise.get_noise_2d(x, z) * height_scale
 
 func _add_tri(st: SurfaceTool, a: Vector3, b: Vector3, c: Vector3, half: float, uv_scale: float) -> void:
 	st.set_uv(Vector2((a.x + half) * uv_scale, (a.z + half) * uv_scale))