Add sunlit shallows site with localized sun shafts

New visual test site under game/world/sites: flat sandy floor at
-40 m, calm surface at 0 m, fixed daytime sun ahead of and above
the submarine. Light shafts come from a shadow-only surface
occluder whose alpha-scissor ripples open only inside a pool a few
tens of metres ahead; a subtractive FogVolume cancels the global
volumetric fog above the water, and an unshaded ceiling mesh shows
the lit underside of the surface inside that pool. A composed
world (sunlit_shallows_world.tscn) mounts the submarine, cockpit
and camera rig in it, with the projectors kept out of the fog.

Cockpit: the porthole glass moves to its own render layer with a
rougher material and the porthole fill light excludes that layer,
so interior lamps no longer mirror as hard specular points.

Quality gate: new integration suite for the site (42 checks), three
glass assertions in the foundation suite, and the Input-access
architecture rule now matches both path separators so the gate runs
on Windows. project.godot raises the volumetric fog froxel grid to
128 so the shafts stay readable.

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

game/world/sites/sunlit_shallows_caustic_floor.gdshader

@@ -0,0 +1,28 @@
+// Flat sandy floor with slowly drifting caustic lines. The pattern is purely
+// presentational and time-driven by the shader clock; no gameplay reads it.
+shader_type spatial;
+
+uniform vec3 sand_color : source_color = vec3(0.34, 0.32, 0.25);
+uniform vec3 caustic_tint : source_color = vec3(0.55, 0.82, 0.92);
+uniform sampler2D caustic_noise : repeat_enable, filter_linear_mipmap;
+uniform float caustic_scale = 0.055;
+uniform float caustic_speed = 0.018;
+uniform float caustic_strength : hint_range(0.0, 2.0) = 0.25;
+
+varying vec2 world_xz;
+
+void vertex() {
+	world_xz = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xz;
+}
+
+void fragment() {
+	vec2 drift_a = TIME * caustic_speed * vec2(1.0, 0.6);
+	vec2 drift_b = TIME * caustic_speed * vec2(-0.7, 1.0);
+	float layer_a = texture(caustic_noise, world_xz * caustic_scale + drift_a).r;
+	float layer_b = texture(caustic_noise, world_xz * caustic_scale * 1.35 + drift_b).r;
+	float caustic = pow(clamp(min(layer_a, layer_b) * 1.9, 0.0, 1.0), 4.0);
+	ALBEDO = sand_color;
+	ROUGHNESS = 0.95;
+	METALLIC = 0.0;
+	EMISSION = caustic_tint * caustic * caustic_strength;
+}

game/world/sites/sunlit_shallows_environment.gd

@@ -0,0 +1,161 @@
+class_name SunlitShallowsEnvironment
+extends Node3D
+
+## Visual test site: flat floor, calm water, fixed daytime sun.
+## The hour never changes, so the sun transform is a constant and the only
+## motion is the slow ripple drift inside the two shaders.
+
+const SURFACE_LEVEL_M := 0.0
+const FLOOR_DEPTH_M := -40.0
+## Air above the calm surface holds no scattering medium: a subtractive
+## FogVolume cancels the global volumetric fog there so the view never shows
+## an unshadowed glow above the water.
+const AIR_VOLUME_HEIGHT_M := 80.0
+const VOLUMETRIC_FOG_DENSITY := 0.035
+const SITE_EXTENT_M := 240.0
+## Sun sits ahead of the observer (world -Z) and high: shafts travel down
+## toward the submarine, as in the cockpit visual target.
+const SUN_ROTATION_DEGREES := Vector3(-44.0, 162.0, 0.0)
+const NOISE_SEED := 7
+## Calm water: ripple drift stays well under 0.05 texture units per second.
+const SURFACE_DRIFT_SPEED := 0.012
+## Sunlight only breaks through a pool of surface a few tens of metres ahead of
+## the submarine (world -Z), so the shafts land in front of the porthole.
+const SHAFT_POOL_CENTER_XZ_M := Vector2(-14.0, -31.0)
+const SHAFT_POOL_RADIUS_M := 22.0
+const SHAFT_POOL_EDGE_M := 12.0
+## Coarser ripples give a few broken oblique shafts rather than a dense fan.
+const SURFACE_RIPPLE_SCALE := 0.025
+## The underside of the surface is drawn dark, lit only inside the pool.
+const SURFACE_CEILING_LIT_SCALE := 0.3
+
+const SURFACE_OCCLUDER_SHADER := preload(
+	"res://game/world/sites/sunlit_shallows_surface_occluder.gdshader"
+)
+const CAUSTIC_FLOOR_SHADER := preload(
+	"res://game/world/sites/sunlit_shallows_caustic_floor.gdshader"
+)
+const SURFACE_CEILING_SHADER := preload(
+	"res://game/world/sites/sunlit_shallows_surface_ceiling.gdshader"
+)
+
+
+func _ready() -> void:
+	_fix_sun()
+	_add_flat_floor()
+	_add_surface_occluder()
+	_add_surface_ceiling()
+	_add_air_fog_cut()
+
+
+func _fix_sun() -> void:
+	var sun := get_node_or_null("Sun") as DirectionalLight3D
+	if sun == null:
+		return
+	sun.rotation_degrees = SUN_ROTATION_DEGREES
+
+
+func _add_flat_floor() -> void:
+	var plane := PlaneMesh.new()
+	plane.size = Vector2(SITE_EXTENT_M, SITE_EXTENT_M)
+	plane.subdivide_width = 1
+	plane.subdivide_depth = 1
+
+	var material := ShaderMaterial.new()
+	material.shader = CAUSTIC_FLOOR_SHADER
+	material.set_shader_parameter("caustic_noise", _make_ripple_noise(0.007))
+
+	var body := StaticBody3D.new()
+	body.name = "FlatFloor"
+	body.position = Vector3(0.0, FLOOR_DEPTH_M, 0.0)
+	body.set_meta("sonar_material", 1)
+	body.set_meta("sonar_reflectivity", 0.6)
+
+	var mesh_instance := MeshInstance3D.new()
+	mesh_instance.name = "Mesh"
+	mesh_instance.mesh = plane
+	mesh_instance.material_override = material
+	body.add_child(mesh_instance)
+
+	var collision := CollisionShape3D.new()
+	collision.name = "Collision"
+	var shape := BoxShape3D.new()
+	shape.size = Vector3(SITE_EXTENT_M, 1.0, SITE_EXTENT_M)
+	collision.shape = shape
+	collision.position = Vector3(0.0, -0.5, 0.0)
+	body.add_child(collision)
+	add_child(body)
+
+
+func _add_surface_occluder() -> void:
+	var plane := PlaneMesh.new()
+	plane.size = Vector2(SITE_EXTENT_M, SITE_EXTENT_M)
+
+	var material := ShaderMaterial.new()
+	material.shader = SURFACE_OCCLUDER_SHADER
+	material.set_shader_parameter("ripple_noise", _make_ripple_noise(0.009))
+	material.set_shader_parameter("drift_speed", SURFACE_DRIFT_SPEED)
+	material.set_shader_parameter("ripple_scale", SURFACE_RIPPLE_SCALE)
+	material.set_shader_parameter("pool_center_xz", SHAFT_POOL_CENTER_XZ_M)
+	material.set_shader_parameter("pool_radius", SHAFT_POOL_RADIUS_M)
+	material.set_shader_parameter("pool_edge", SHAFT_POOL_EDGE_M)
+
+	var occluder := MeshInstance3D.new()
+	occluder.name = "CalmSurfaceOccluder"
+	occluder.position = Vector3(0.0, SURFACE_LEVEL_M, 0.0)
+	occluder.mesh = plane
+	occluder.material_override = material
+	occluder.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_SHADOWS_ONLY
+	add_child(occluder)
+
+
+func _add_surface_ceiling() -> void:
+	var plane := PlaneMesh.new()
+	plane.size = Vector2(SITE_EXTENT_M * 1.5, SITE_EXTENT_M * 1.5)
+
+	var material := ShaderMaterial.new()
+	material.shader = SURFACE_CEILING_SHADER
+	material.set_shader_parameter("ripple_noise", _make_ripple_noise(0.009))
+	material.set_shader_parameter("drift_speed", SURFACE_DRIFT_SPEED)
+	material.set_shader_parameter("pool_center_xz", SHAFT_POOL_CENTER_XZ_M)
+	material.set_shader_parameter("pool_radius", SHAFT_POOL_RADIUS_M)
+	material.set_shader_parameter("lit_scale", SURFACE_CEILING_LIT_SCALE)
+
+	var ceiling := MeshInstance3D.new()
+	ceiling.name = "SurfaceCeiling"
+	ceiling.position = Vector3(0.0, SURFACE_LEVEL_M, 0.0)
+	ceiling.mesh = plane
+	ceiling.material_override = material
+	ceiling.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
+	add_child(ceiling)
+
+
+func _add_air_fog_cut() -> void:
+	var air := FogVolume.new()
+	air.name = "AirFogCut"
+	air.shape = RenderingServer.FOG_VOLUME_SHAPE_BOX
+	air.size = Vector3(SITE_EXTENT_M * 1.5, AIR_VOLUME_HEIGHT_M, SITE_EXTENT_M * 1.5)
+	air.position = Vector3(0.0, SURFACE_LEVEL_M + AIR_VOLUME_HEIGHT_M * 0.5, 0.0)
+	var material := FogMaterial.new()
+	material.density = -VOLUMETRIC_FOG_DENSITY
+	material.edge_fade = 0.0
+	air.material = material
+	add_child(air)
+
+
+func _make_ripple_noise(frequency: float) -> NoiseTexture2D:
+	var noise := FastNoiseLite.new()
+	noise.seed = NOISE_SEED
+	noise.noise_type = FastNoiseLite.TYPE_SIMPLEX_SMOOTH
+	noise.frequency = frequency
+	noise.fractal_octaves = 3
+	noise.fractal_lacunarity = 2.1
+	noise.fractal_gain = 0.45
+
+	var texture := NoiseTexture2D.new()
+	texture.width = 512
+	texture.height = 512
+	texture.seamless = true
+	texture.generate_mipmaps = true
+	texture.noise = noise
+	return texture

game/world/sites/sunlit_shallows_environment.tscn

@@ -0,0 +1,64 @@
+[gd_scene load_steps=3 format=3]
+
+[ext_resource type="Script" path="res://game/world/sites/sunlit_shallows_environment.gd" id="1_environment"]
+
+[sub_resource type="Environment" id="EnvironmentSunlitShallows"]
+background_mode = 1
+background_color = Color(0.005, 0.03, 0.06, 1)
+ambient_light_source = 3
+ambient_light_color = Color(0.14, 0.32, 0.42, 1)
+ambient_light_energy = 0.22
+tonemap_mode = 2
+tonemap_exposure = 0.75
+glow_enabled = true
+glow_levels/1 = 0.6
+glow_levels/2 = 1.0
+glow_levels/3 = 0.8
+glow_levels/4 = 0.3
+glow_intensity = 0.35
+glow_blend_mode = 0
+glow_hdr_threshold = 1.6
+fog_enabled = true
+fog_light_color = Color(0.04, 0.16, 0.24, 1)
+fog_light_energy = 0.12
+fog_sun_scatter = 0.0
+fog_density = 0.003
+fog_aerial_perspective = 0.6
+fog_sky_affect = 1.0
+volumetric_fog_enabled = true
+volumetric_fog_density = 0.035
+volumetric_fog_albedo = Color(0.26, 0.52, 0.7, 1)
+volumetric_fog_emission_energy = 0.0
+volumetric_fog_anisotropy = 0.55
+volumetric_fog_length = 150.0
+volumetric_fog_detail_spread = 1.6
+volumetric_fog_ambient_inject = 0.015
+volumetric_fog_sky_affect = 1.0
+volumetric_fog_temporal_reprojection_enabled = true
+volumetric_fog_temporal_reprojection_amount = 0.92
+
+[node name="SunlitShallowsEnvironment" type="Node3D"]
+script = ExtResource("1_environment")
+
+[node name="WorldEnvironment" type="WorldEnvironment" parent="."]
+environment = SubResource("EnvironmentSunlitShallows")
+
+[node name="Sun" type="DirectionalLight3D" parent="."]
+rotation_degrees = Vector3(-44, 162, 0)
+light_color = Color(0.86, 0.95, 1, 1)
+light_energy = 1.0
+light_volumetric_fog_energy = 1.4
+shadow_enabled = true
+shadow_bias = 0.04
+shadow_normal_bias = 1.5
+shadow_blur = 2.5
+directional_shadow_mode = 1
+directional_shadow_split_1 = 0.2
+directional_shadow_blend_splits = true
+directional_shadow_max_distance = 160.0
+
+[node name="ObserverCamera" type="Camera3D" parent="."]
+transform = Transform3D(1, 0, 0, 0, 0.9962, 0.0872, 0, -0.0872, 0.9962, 0, -30, 0)
+fov = 72.0
+near = 0.1
+far = 400.0

game/world/sites/sunlit_shallows_surface_ceiling.gdshader

@@ -0,0 +1,32 @@
+// Underside of the calm surface as seen from below: dark everywhere, lit with
+// drifting crests only inside the pool where the occluder lets the sun through.
+// Purely visual; shadows and shafts come from the occluder mesh.
+shader_type spatial;
+render_mode unshaded, cull_disabled;
+
+uniform sampler2D ripple_noise : repeat_enable, filter_linear_mipmap;
+uniform vec2 pool_center_xz = vec2(-14.0, -31.0);
+uniform float pool_radius = 22.0;
+uniform float ripple_scale = 0.03;
+uniform float drift_speed = 0.012;
+uniform float lit_scale : hint_range(0.0, 1.0) = 0.3;
+uniform vec3 dark_color : source_color = vec3(0.01, 0.05, 0.09);
+uniform vec3 lit_color : source_color = vec3(0.5, 0.85, 1.0);
+
+varying vec2 world_xz;
+
+void vertex() {
+	world_xz = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xz;
+}
+
+void fragment() {
+	vec2 slow_drift = vec2(TIME * drift_speed);
+	vec2 cross_drift = vec2(-TIME * drift_speed * 0.7);
+	float broad = texture(ripple_noise, world_xz * ripple_scale + slow_drift).r;
+	float fine = texture(ripple_noise, world_xz * ripple_scale * 1.9 + cross_drift).r;
+	float crest = smoothstep(0.45, 0.7, broad * 0.65 + fine * 0.35);
+	float pool = 1.0 - smoothstep(
+		pool_radius * 0.6, pool_radius * 1.6, distance(world_xz, pool_center_xz)
+	);
+	ALBEDO = mix(dark_color, lit_color * (0.35 + crest) * lit_scale, pool);
+}

game/world/sites/sunlit_shallows_surface_occluder.gdshader

@@ -0,0 +1,39 @@
+// Calm-water surface seen only through its shadow: the mesh is invisible
+// (SHADOW_ONLY) and the alpha-scissor cut-outs let the fixed daytime sun carve
+// light shafts into the volumetric fog below.
+shader_type spatial;
+render_mode cull_disabled, unshaded, depth_prepass_alpha;
+
+uniform sampler2D ripple_noise : repeat_enable, filter_linear_mipmap;
+uniform float ripple_scale = 0.025;
+uniform float drift_speed = 0.012;
+uniform float coverage : hint_range(0.0, 1.0) = 0.30;
+// World-space pool where the surface lets sunlight through. Outside it the
+// surface is fully opaque, so shafts only form in that patch of water.
+uniform vec2 pool_center_xz = vec2(-14.0, -31.0);
+uniform float pool_radius = 22.0;
+uniform float pool_edge = 12.0;
+
+varying vec2 world_xz;
+
+void vertex() {
+	world_xz = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xz;
+}
+
+void fragment() {
+	vec2 slow_drift = TIME * drift_speed * vec2(1.0, 0.35);
+	vec2 cross_drift = TIME * drift_speed * vec2(-0.4, 0.9);
+	float broad = texture(ripple_noise, world_xz * ripple_scale + slow_drift).r;
+	float fine = texture(ripple_noise, world_xz * ripple_scale * 1.9 + cross_drift).r;
+	float raw_ripple = broad * 0.65 + fine * 0.35;
+	// Inside the pool the crests are sharpened so the gaps cut crisp shafts.
+	float pool_ripple = smoothstep(0.35, 0.65, raw_ripple);
+	// Outside the pool only the deepest troughs open: a dim dapple, not darkness.
+	float dim_ripple = smoothstep(0.16, 0.30, raw_ripple);
+	float pool = 1.0 - smoothstep(
+		pool_radius - pool_edge, pool_radius, distance(world_xz, pool_center_xz)
+	);
+	ALBEDO = vec3(0.0);
+	ALPHA = mix(dim_ripple, pool_ripple, pool);
+	ALPHA_SCISSOR_THRESHOLD = coverage;
+}