feat(tools): Outcrop and BoulderField primitives with forced rock material

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/unit/run_site_baker_tests.gd

@@ -8,7 +8,7 @@ const SiteTerrainData = preload("res://game/domain/sites/site_terrain_data.gd")
 
 const ZONE1_TERRAIN_PATH := "res://content/sites/zone1_vigilant_terrain.res"
 
-const TEST_COUNT := 26
+const TEST_COUNT := 36
 
 var _failures: Array[String] = []
 
@@ -20,6 +20,8 @@ func _init() -> void:
 	_test_zone1_artefact_is_stable()
 	_test_canyon()
 	_test_escarpment()
+	_test_outcrop()
+	_test_boulder_field()
 
 	if _failures.is_empty():
 		print("Site baker unit tests: %d passed, 0 failed." % TEST_COUNT)
@@ -144,6 +146,34 @@ func _test_escarpment() -> void:
 	_expect(is_equal_approx(cliff.elevation_delta(0.0, 12.0), -15.0), "escarpment keeps falling at slope_beyond")
 
 
+func _test_outcrop() -> void:
+	var mesa := SiteTerrainBaker.Outcrop.new(Vector2.ZERO, 10.0, 10.0, 6.0, 4.0, 0, 0.0, true)
+	_expect(is_equal_approx(mesa.elevation_delta(0.0, 0.0), 6.0), "outcrop top is flat at height_m")
+	_expect(is_equal_approx(mesa.elevation_delta(0.0, 8.0), 3.0), "outcrop flank is half way down in the middle of the wall")
+	_expect(is_equal_approx(mesa.elevation_delta(0.0, 25.0), 0.0), "outcrop is zero past its outline")
+	_expect(mesa.material_at(0.0, 0.0) == SonarMaterial.Value.ROCK, "rock_top makes the flat summit rock")
+	_expect(mesa.material_at(0.0, 25.0) == SiteTerrainBaker.NO_MATERIAL, "outcrop leaves the surroundings to the slope rule")
+	var sand_top := SiteTerrainBaker.Outcrop.new(Vector2.ZERO, 10.0, 10.0, 6.0, 4.0, 0, 0.0, false)
+	_expect(sand_top.material_at(0.0, 0.0) == SiteTerrainBaker.NO_MATERIAL, "without rock_top the summit follows the slope rule")
+	var pit := SiteTerrainBaker.Outcrop.new(Vector2.ZERO, 10.0, 20.0, -5.0, 3.0, 0, 0.0, false)
+	_expect(is_equal_approx(pit.elevation_delta(0.0, 0.0), -5.0), "negative height digs a flat-bottomed pit")
+
+
+func _test_boulder_field() -> void:
+	var first := SiteTerrainBaker.BoulderField.new(Vector2(50.0, -50.0), 30.0, 11, 20, 2.0, 4.0, 0.8)
+	var second := SiteTerrainBaker.BoulderField.new(Vector2(50.0, -50.0), 30.0, 11, 20, 2.0, 4.0, 0.8)
+	_expect(first.boulders() == second.boulders(), "same seed scatters the same boulders")
+	var all_inside := true
+	for boulder in first.boulders():
+		all_inside = all_inside and Vector2(boulder.x, boulder.y).distance_to(Vector2(50.0, -50.0)) <= 30.0
+	_expect(all_inside and first.boulders().size() == 20, "boulders stay inside the field disc")
+	var top := first.boulders()[0]
+	_expect(first.elevation_delta(top.x, top.y) >= top.z * 0.8 - 0.001, "a boulder centre is at least its own height")
+	_expect(first.material_at(top.x, top.y) == SonarMaterial.Value.ROCK and first.material_at(200.0, 200.0) == SiteTerrainBaker.NO_MATERIAL, "boulders are rock, the sand around is not forced")
+	var stacked := SiteTerrainBaker.BoulderField.new(Vector2.ZERO, 0.0, 3, 5, 2.0, 4.0, 1.0)
+	_expect(stacked.elevation_delta(0.0, 0.0) <= 4.0 + 0.001, "overlapping boulders combine by maximum, not by sum")
+
+
 func _test_zone1_artefact_is_stable() -> void:
 	var versioned := load(ZONE1_TERRAIN_PATH) as SiteTerrainData
 	_expect(versioned != null, "versioned zone 1 terrain loads")

tools/site_terrain_baker.gd

@@ -243,6 +243,110 @@ class Escarpment extends Primitive:
 		return -(step + slope)
 
 
+## Flat-topped elliptical mound (or, with a negative height, a flat-bottomed pit) whose
+## flank spans wall_width_m inside a noise-roughened outline. With rock_top the whole
+## mound above 30 % of its height is rock, sommet plat compris.
+class Outcrop extends Primitive:
+	var centre: Vector2
+	var radius_x_m: float
+	var radius_z_m: float
+	var height_m: float
+	var wall_width_m: float
+	var edge_amplitude_m: float
+	var rock_top: bool
+	var _noise: FastNoiseLite
+	var _mean_radius_m: float
+
+	func _init(
+		p_centre: Vector2,
+		p_radius_x_m: float,
+		p_radius_z_m: float,
+		p_height_m: float,
+		p_wall_width_m: float,
+		p_edge_seed: int,
+		p_edge_amplitude_m: float,
+		p_rock_top: bool
+	) -> void:
+		centre = p_centre
+		radius_x_m = p_radius_x_m
+		radius_z_m = p_radius_z_m
+		height_m = p_height_m
+		wall_width_m = p_wall_width_m
+		edge_amplitude_m = p_edge_amplitude_m
+		rock_top = p_rock_top
+		_noise = edge_noise(p_edge_seed, p_edge_amplitude_m)
+		_mean_radius_m = (p_radius_x_m + p_radius_z_m) * 0.5
+
+	func elevation_delta(x_m: float, z_m: float) -> float:
+		var dx := (x_m - centre.x) / radius_x_m
+		var dz := (z_m - centre.y) / radius_z_m
+		var edge_distance := (sqrt(dx * dx + dz * dz) - 1.0) * _mean_radius_m
+		edge_distance += edge_offset(_noise, edge_amplitude_m, x_m, z_m)
+		return height_m * (1.0 - smoothstep(-wall_width_m, 0.0, edge_distance))
+
+	func material_at(x_m: float, z_m: float) -> int:
+		if rock_top and absf(elevation_delta(x_m, z_m)) > 0.3 * absf(height_m):
+			return SonarMaterial.Value.ROCK
+		return NO_MATERIAL
+
+
+## count half-ellipsoid boulders scattered uniformly in a disc by a seeded generator.
+## Boulders combine by maximum, so overlapping blocks never pile into one mound, and every
+## cell they cover is rock.
+class BoulderField extends Primitive:
+	var centre: Vector2
+	var radius_m: float
+	var height_ratio: float
+	var _boulders := PackedVector3Array()  # x, z, radius
+	var _reach_m: float
+
+	func _init(
+		p_centre: Vector2,
+		p_radius_m: float,
+		p_seed: int,
+		p_count: int,
+		p_boulder_radius_min_m: float,
+		p_boulder_radius_max_m: float,
+		p_height_ratio: float
+	) -> void:
+		centre = p_centre
+		radius_m = p_radius_m
+		height_ratio = p_height_ratio
+		_reach_m = p_radius_m + p_boulder_radius_max_m
+		var generator := RandomNumberGenerator.new()
+		generator.seed = p_seed
+		for _index in p_count:
+			var distance := p_radius_m * sqrt(generator.randf())
+			var angle := TAU * generator.randf()
+			var boulder_radius := generator.randf_range(p_boulder_radius_min_m, p_boulder_radius_max_m)
+			_boulders.append(Vector3(
+				p_centre.x + distance * cos(angle),
+				p_centre.y + distance * sin(angle),
+				boulder_radius
+			))
+
+	func boulders() -> PackedVector3Array:
+		return _boulders
+
+	func elevation_delta(x_m: float, z_m: float) -> float:
+		if Vector2(x_m, z_m).distance_to(centre) > _reach_m:
+			return 0.0
+		var highest := 0.0
+		for boulder in _boulders:
+			var dx := x_m - boulder.x
+			var dz := z_m - boulder.y
+			var squared := dx * dx + dz * dz
+			var radius_squared := boulder.z * boulder.z
+			if squared < radius_squared:
+				highest = maxf(highest, boulder.z * height_ratio * sqrt(1.0 - squared / radius_squared))
+		return highest
+
+	func material_at(x_m: float, z_m: float) -> int:
+		if elevation_delta(x_m, z_m) > 0.0:
+			return SonarMaterial.Value.ROCK
+		return NO_MATERIAL
+
+
 class Step extends Primitive:
 	var point: Vector2
 	var normal: Vector2