fix clam surface spawn validation

network/network_world_spawn_service.gd

@@ -518,7 +518,12 @@ func _sample_surface_position(
 	)
 	if triangles.is_empty() or total_area <= 0.0:
 		return Vector3(INF, INF, INF)
-	var attempts: int = 48 if is_finite(maximum_distance) else 1
+	var validates_diggable_surface := not entry.diggable_area_id.is_empty()
+	var attempts: int = (
+		48
+		if validates_diggable_surface or is_finite(maximum_distance)
+		else 1
+	)
 	var fallback: Vector3 = Vector3(INF, INF, INF)
 	for _attempt: int in attempts:
 		var roll: float = _rng.randf() * total_area
@@ -534,12 +539,22 @@ func _sample_surface_position(
 			+ triangle[2] * barycentric_c
 		)
 		fallback = point
-		if (
+		var within_requested_distance := (
 			not is_finite(maximum_distance)
 			or Vector2(point.x - origin.x, point.z - origin.z).length()
 			<= maximum_distance
-		):
+		)
+		var valid_diggable_surface := (
+			not validates_diggable_surface
+			or _world.is_diggable_surface_point_valid(
+				entry.diggable_area_id,
+				point,
+			)
+		)
+		if within_requested_distance and valid_diggable_surface:
 			return point
+	if validates_diggable_surface:
+		return Vector3(INF, INF, INF)
 	if origin.is_finite() and is_finite(maximum_distance):
 		return origin
 	return fallback

tests/digging_prototype_validation.gd

@@ -14,11 +14,11 @@ const Gatherables: GatherableCatalog = preload(
 class PrimaryTerrainProvider:
 	extends Node3D
 
-	var primary_mesh: MeshInstance3D
+	var primary_meshes: Array[MeshInstance3D] = []
 
 
 	func get_primary_terrain_meshes() -> Array[MeshInstance3D]:
-		return [primary_mesh] if primary_mesh != null else []
+		return primary_meshes
 
 
 func _initialize() -> void:
@@ -98,9 +98,17 @@ func _validate_primary_terrain_provider() -> void:
 	var provider := PrimaryTerrainProvider.new()
 	provider.name = "Provider"
 	fixture.add_child(provider)
-	provider.primary_mesh = _flat_sand_triangle(0.0)
+	var clear_sand := _flat_surface_triangle(0.0, 0.0, &"sand")
-	provider.add_child(provider.primary_mesh)
+	var covered_sand := _flat_surface_triangle(10.0, 0.0, &"sand")
-	var buried_base := _flat_sand_triangle(10.0)
+	var covering_grass := _flat_surface_triangle(10.0, 0.01, &"grass_lite")
+	for mesh_instance: MeshInstance3D in [
+		clear_sand,
+		covered_sand,
+		covering_grass,
+	]:
+		provider.add_child(mesh_instance)
+		provider.primary_meshes.append(mesh_instance)
+	var buried_base := _flat_surface_triangle(20.0, 0.0, &"sand")
 	buried_base.name = "BuriedSandBase"
 	provider.add_child(buried_base)
 	var area := DiggableArea3D.new()
@@ -111,28 +119,34 @@ func _validate_primary_terrain_provider() -> void:
 	area.generation_bounds = Rect2(-20.0, -20.0, 40.0, 40.0)
 	fixture.add_child(area)
 	var triangles := area.get_surface_triangles()
-	assert(triangles.size() == 1)
+	assert(triangles.size() == 2)
-	var center := (triangles[0][0] + triangles[0][1] + triangles[0][2]) / 3.0
+	var clear_center := Vector3(1.0 / 3.0, 0.0, 1.0 / 3.0)
-	assert(center.x < 2.0)
+	var covered_center := Vector3(10.0 + 1.0 / 3.0, 0.0, 1.0 / 3.0)
+	assert(area.is_surface_point_valid(clear_center))
+	assert(not area.is_surface_point_valid(covered_center))
 	fixture.free()
 
 
-func _flat_sand_triangle(x_offset: float) -> MeshInstance3D:
+func _flat_surface_triangle(
+	x_offset: float,
+	height: float,
+	material_name: StringName,
+) -> MeshInstance3D:
 	var arrays: Array = []
 	arrays.resize(Mesh.ARRAY_MAX)
 	arrays[Mesh.ARRAY_VERTEX] = PackedVector3Array([
-		Vector3(x_offset, 0.0, 0.0),
+		Vector3(x_offset, height, 0.0),
-		Vector3(x_offset, 0.0, 1.0),
+		Vector3(x_offset, height, 1.0),
-		Vector3(x_offset + 1.0, 0.0, 0.0),
+		Vector3(x_offset + 1.0, height, 0.0),
 	])
 	arrays[Mesh.ARRAY_INDEX] = PackedInt32Array([0, 1, 2])
 	var mesh := ArrayMesh.new()
 	mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)
 	var material := StandardMaterial3D.new()
-	material.resource_name = "sand"
+	material.resource_name = str(material_name)
 	mesh.surface_set_material(0, material)
 	var mesh_instance := MeshInstance3D.new()
-	mesh_instance.name = "PrimarySand"
+	mesh_instance.name = "Primary%s" % str(material_name).capitalize()
 	mesh_instance.mesh = mesh
 	return mesh_instance
 

world/digging/diggable_area_3d.gd

@@ -2,6 +2,10 @@
 class_name DiggableArea3D
 extends Node3D
 
+const SURFACE_HEIGHT_TOLERANCE := 0.015
+const SURFACE_BOUNDS_TOLERANCE := 0.001
+const MINIMUM_VALIDATION_UP_DOT := 0.01
+
 @export var area_id: StringName
 @export_node_path("Node3D") var terrain_source: NodePath
 @export var surface_materials: Array[StringName] = []
@@ -10,9 +14,14 @@ extends Node3D
 @export_range(-100.0, 100.0, 0.01) var maximum_global_y: float = 100.0
 @export_range(0.0, 1.0, 0.01) var minimum_up_dot: float = 0.6
 
+var _surface_validation_groups: Array[Dictionary] = []
+var _surface_validation_ready := false
+
 
 func get_surface_triangles() -> Array[PackedVector3Array]:
 	var triangles: Array[PackedVector3Array] = []
+	_surface_validation_groups.clear()
+	_surface_validation_ready = false
 	if area_id.is_empty() or surface_materials.is_empty():
 		return triangles
 	var terrain_root: Node = get_node_or_null(terrain_source)
@@ -22,25 +31,90 @@ func get_surface_triangles() -> Array[PackedVector3Array]:
 		var mesh: Mesh = mesh_instance.mesh
 		if mesh == null:
 			continue
+		var validation_records: Array[Dictionary] = []
+		var validation_bounds := Rect2()
+		var has_validation_bounds := false
 		for surface_index: int in mesh.get_surface_count():
 			var material: Material = mesh_instance.get_active_material(surface_index)
-			if (
+			var allowed_surface := (
-				material == null
+				material != null
-				or not surface_materials.has(StringName(material.resource_name))
+				and surface_materials.has(StringName(material.resource_name))
-			):
+			)
-				continue
 			_append_surface_triangles(
 				triangles,
+				validation_records,
 				mesh_instance,
 				mesh.surface_get_arrays(surface_index),
+				allowed_surface,
 			)
+		for record: Dictionary in validation_records:
+			var record_bounds: Rect2 = record.get("bounds", Rect2())
+			if not has_validation_bounds:
+				validation_bounds = record_bounds
+				has_validation_bounds = true
+			else:
+				validation_bounds = validation_bounds.merge(record_bounds)
+		if not validation_records.is_empty():
+			_surface_validation_groups.append({
+				"bounds": validation_bounds,
+				"records": validation_records,
+			})
+	_surface_validation_ready = true
 	return triangles
 
 
+func invalidate_surface_cache() -> void:
+	_surface_validation_groups.clear()
+	_surface_validation_ready = false
+
+
+func is_surface_point_valid(point: Vector3) -> bool:
+	if not point.is_finite():
+		return false
+	if not _surface_validation_ready:
+		get_surface_triangles()
+	var sample := Vector2(point.x, point.z)
+	var highest_y := -INF
+	var highest_is_allowed := false
+	var found_surface := false
+	for group: Dictionary in _surface_validation_groups:
+		var group_bounds: Rect2 = group.get("bounds", Rect2())
+		if not group_bounds.grow(SURFACE_BOUNDS_TOLERANCE).has_point(sample):
+			continue
+		var records: Array = group.get("records", [])
+		for record: Dictionary in records:
+			var record_bounds: Rect2 = record.get("bounds", Rect2())
+			if not record_bounds.grow(SURFACE_BOUNDS_TOLERANCE).has_point(sample):
+				continue
+			var triangle := record.get(
+				"triangle", PackedVector3Array()
+			) as PackedVector3Array
+			var surface_y := _surface_height_at_point(triangle, sample)
+			if not is_finite(surface_y):
+				continue
+			var allowed := bool(record.get("allowed", false))
+			if surface_y > highest_y + SURFACE_HEIGHT_TOLERANCE:
+				highest_y = surface_y
+				highest_is_allowed = allowed
+				found_surface = true
+			elif absf(surface_y - highest_y) <= SURFACE_HEIGHT_TOLERANCE:
+				# Material seams may expose coplanar grass and sand triangles.
+				# Treat any tied disallowed surface as authoritative so a dig
+				# hotspot can never appear in visually grassy terrain.
+				highest_is_allowed = highest_is_allowed and allowed
+	return (
+		found_surface
+		and highest_is_allowed
+		and absf(highest_y - point.y) <= SURFACE_HEIGHT_TOLERANCE
+	)
+
+
 func _append_surface_triangles(
 	result: Array[PackedVector3Array],
+	validation_records: Array[Dictionary],
 	mesh_instance: MeshInstance3D,
 	arrays: Array,
+	allowed_surface: bool,
 ) -> void:
 	if arrays.size() <= Mesh.ARRAY_INDEX:
 		return
@@ -52,26 +126,49 @@ func _append_surface_triangles(
 		for vertex_index: int in range(0, vertices.size() - 2, 3):
 			_append_triangle(
 				result,
+				validation_records,
 				mesh_instance.to_global(vertices[vertex_index]),
 				mesh_instance.to_global(vertices[vertex_index + 1]),
 				mesh_instance.to_global(vertices[vertex_index + 2]),
+				allowed_surface,
 			)
 		return
 	for index_offset: int in range(0, indices.size() - 2, 3):
 		_append_triangle(
 			result,
+			validation_records,
 			mesh_instance.to_global(vertices[indices[index_offset]]),
 			mesh_instance.to_global(vertices[indices[index_offset + 1]]),
 			mesh_instance.to_global(vertices[indices[index_offset + 2]]),
+			allowed_surface,
 		)
 
 
 func _append_triangle(
 	result: Array[PackedVector3Array],
+	validation_records: Array[Dictionary],
 	a: Vector3,
 	b: Vector3,
 	c: Vector3,
+	allowed_surface: bool,
 ) -> void:
+	var cross := (b - a).cross(c - a)
+	if cross.length_squared() <= 0.0000001:
+		return
+	var up_dot := absf(cross.normalized().dot(Vector3.UP))
+	var triangle := PackedVector3Array([a, b, c])
+	var projected_bounds := _projected_bounds(triangle)
+	if (
+		up_dot >= MINIMUM_VALIDATION_UP_DOT
+		and generation_bounds.intersects(projected_bounds, true)
+	):
+		validation_records.append({
+			"allowed": allowed_surface,
+			"bounds": projected_bounds,
+			"triangle": triangle,
+		})
+	if not allowed_surface:
+		return
 	if (
 		a.y < minimum_global_y
 		or b.y < minimum_global_y
@@ -84,12 +181,56 @@ func _append_triangle(
 	var center := (a + b + c) / 3.0
 	if not generation_bounds.has_point(Vector2(center.x, center.z)):
 		return
-	var cross := (b - a).cross(c - a)
+	if up_dot < minimum_up_dot:
-	if cross.length_squared() <= 0.0000001:
 		return
-	if absf(cross.normalized().dot(Vector3.UP)) < minimum_up_dot:
+	result.append(triangle)
-		return
+
-	result.append(PackedVector3Array([a, b, c]))
+
+static func _projected_bounds(triangle: PackedVector3Array) -> Rect2:
+	var minimum := Vector2(triangle[0].x, triangle[0].z)
+	var maximum := minimum
+	for index: int in range(1, triangle.size()):
+		var point := Vector2(triangle[index].x, triangle[index].z)
+		minimum = minimum.min(point)
+		maximum = maximum.max(point)
+	return Rect2(minimum, maximum - minimum)
+
+
+static func _surface_height_at_point(
+	triangle: PackedVector3Array,
+	point: Vector2,
+) -> float:
+	if triangle.size() != 3:
+		return INF
+	var a := Vector2(triangle[0].x, triangle[0].z)
+	var b := Vector2(triangle[1].x, triangle[1].z)
+	var c := Vector2(triangle[2].x, triangle[2].z)
+	var denominator := (
+		(b.y - c.y) * (a.x - c.x)
+		+ (c.x - b.x) * (a.y - c.y)
+	)
+	if absf(denominator) <= 0.0000001:
+		return INF
+	var weight_a := (
+		(b.y - c.y) * (point.x - c.x)
+		+ (c.x - b.x) * (point.y - c.y)
+	) / denominator
+	var weight_b := (
+		(c.y - a.y) * (point.x - c.x)
+		+ (a.x - c.x) * (point.y - c.y)
+	) / denominator
+	var weight_c := 1.0 - weight_a - weight_b
+	if (
+		weight_a < -SURFACE_BOUNDS_TOLERANCE
+		or weight_b < -SURFACE_BOUNDS_TOLERANCE
+		or weight_c < -SURFACE_BOUNDS_TOLERANCE
+	):
+		return INF
+	return (
+		triangle[0].y * weight_a
+		+ triangle[1].y * weight_b
+		+ triangle[2].y * weight_c
+	)
 
 
 func _terrain_mesh_instances(terrain_root: Node) -> Array[MeshInstance3D]:

world/generation/generated_world_region.gd

@@ -191,6 +191,7 @@ func get_spawn_surface_triangles(
 
 
 func _on_generation_completed(summary: Dictionary) -> void:
+	_diggable_beach.invalidate_surface_cache()
 	var records: Array[Dictionary] = _generator.placement_records()
 	_assign_biomes(records, summary)
 	var spawn_position := Vector3.ZERO

world/test_world.gd

@@ -207,6 +207,16 @@ func get_diggable_area_triangles(
 	return []
 
 
+func is_diggable_surface_point_valid(
+	area_id: StringName,
+	point: Vector3,
+) -> bool:
+	if _active_region == null:
+		return false
+	var area: DiggableArea3D = _active_region.get_diggable_area(area_id)
+	return area != null and area.is_surface_point_valid(point)
+
+
 func get_gatherable_spawn_positions(
 	anchor_set_id: StringName,
 ) -> PackedVector3Array: