feat(cockpit): replace procedural cockpit with twelve scripted models

Instance twelve Blender-scripted glTF models in the cockpit scene and
rebuild the cabin around them: gauge panel, sonar, switch panel, alert
box, speaker, porthole, hull wall, caged lamps, gas bottle, handrails
and side consoles. Presentation only; no domain, application or world
rule changes beyond enabling glow in the test environment.

- Needles, alert lamps and sonar screen are driven by the existing
  snapshots; the alert box now carries SYS/ATTN/ALRM.
- Depth dial reads percent of certified depth.
- Sonar display restyled as a turquoise holographic relief with a
  shader grid and height scale; SubViewport matches the glass (960x604).
- Cabin lighting retuned: warm pooled lamp light, cool porthole rim,
  lamp shadows, dial backlight.
- Procedural stand-ins removed (bulkhead, tanks, consoles, levers,
  indicator columns, placeholder pipe run, dial face PNGs).
- Tests adapted where nodes disappeared; one assertion removed
  (pipe_segment_count) until the pipe kit is placed.
- Model .glb files are committed without LFS; textures Godot extracts
  next to them at import are ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

game/presentation/sonar/sonar_display.gd

@@ -61,6 +61,10 @@ func built_grid_segment_count() -> int:
 	return _renderer.built_grid_segment_count()
 
 
+func depth_scale_texts() -> PackedStringArray:
+	return _renderer.depth_scale_texts()
+
+
 func idle_prompt_visible() -> bool:
 	return _renderer.idle_prompt_visible()
 

game/presentation/sonar/sonar_display.tscn

@@ -27,7 +27,7 @@ script = ExtResource("1_display")
 
 [node name="SonarReliefRenderer" type="SubViewport" parent="."]
 unique_name_in_owner = true
-size = Vector2i(960, 540)
+size = Vector2i(960, 604)
 render_target_update_mode = 4
 script = ExtResource("2_renderer")
 
@@ -77,4 +77,4 @@ text = "SONAR PRÊT · F POUR ÉMETTRE"
 [node name="Legend" type="Label" parent="ExpandedPanel/Layout"]
 layout_mode = 2
 theme_override_colors/font_color = Color(0.58, 0.7, 0.71, 1)
-text = "BLEU PROFOND · VERT/JAUNE HAUTEUR · ORANGE ANOMALIE · NOIR INCONNU · TAB FERMER"
+text = "TURQUOISE SOMBRE PROFOND · CYAN CLAIR HAUTEUR · ORANGE ANOMALIE · NOIR INCONNU · TAB FERMER"

game/presentation/sonar/sonar_relief_mesh_builder.gd

@@ -5,53 +5,59 @@ const SonarMaterial = preload("res://game/domain/sonar/sonar_material.gd")
 const SonarSample = preload("res://game/domain/sonar/sonar_sample.gd")
 const SonarScan = preload("res://game/domain/sonar/sonar_scan.gd")
 
-const COLOR_DEEP := Color("173f91")
-const COLOR_LOW := Color("168fc1")
-const COLOR_MIDDLE := Color("36b979")
-const COLOR_HIGH := Color("d7d93d")
-const COLOR_PEAK := Color("ee5734")
-const COLOR_METAL := Color("ff6b22")
+## Grid lines are drawn by the relief shader on the cell edges: every built
+## cell carries one row edge and one column edge of the grid.
+const GRID_SEGMENTS_PER_CELL := 2
+## Two triangles per cell, wound like the sample grid.
+const CELL_CORNER_ORDER: Array[int] = [0, 2, 1, 1, 2, 3]
 
 
-static func build_full_mesh(
-	scan: SonarScan,
-	material: StandardMaterial3D
-) -> ArrayMesh:
+static func build_full_mesh(scan: SonarScan, material: Material) -> ArrayMesh:
 	var mesh := ArrayMesh.new()
 	for row in range(1, scan.samples.rows):
 		add_row_band(mesh, scan, row, material)
 	return mesh
 
 
+## Adds the cells between `row - 1` and `row`; returns the triangle count.
+## Per vertex: UV = (column, row) of the sample grid, COLOR.r = height relative
+## to the scan (0 low, 1 peak), COLOR.g = 1 on metal, COLOR.b = echo intensity.
 static func add_row_band(
 	mesh: ArrayMesh,
 	scan: SonarScan,
 	row: int,
-	material: StandardMaterial3D
+	material: Material
 ) -> int:
 	var vertices := PackedVector3Array()
 	var normals := PackedVector3Array()
 	var colors := PackedColorArray()
+	var uvs := PackedVector2Array()
 	for column in range(scan.samples.columns - 1):
-		var top_left: SonarSample = scan.samples.sample_at(row - 1, column)
-		var top_right: SonarSample = scan.samples.sample_at(row - 1, column + 1)
-		var bottom_left: SonarSample = scan.samples.sample_at(row, column)
-		var bottom_right: SonarSample = scan.samples.sample_at(row, column + 1)
+		var corners: Array[SonarSample] = [
+			scan.samples.sample_at(row - 1, column),
+			scan.samples.sample_at(row - 1, column + 1),
+			scan.samples.sample_at(row, column),
+			scan.samples.sample_at(row, column + 1),
+		]
 		if not (
-			top_left.observed
-			and top_right.observed
-			and bottom_left.observed
-			and bottom_right.observed
+			corners[0].observed
+			and corners[1].observed
+			and corners[2].observed
+			and corners[3].observed
 		):
 			continue
-		_append_triangle(
-			vertices, normals, colors, scan,
-			top_left, bottom_left, top_right
-		)
-		_append_triangle(
-			vertices, normals, colors, scan,
-			top_right, bottom_left, bottom_right
-		)
+		var grid: Array[Vector2] = [
+			Vector2(column, row - 1),
+			Vector2(column + 1, row - 1),
+			Vector2(column, row),
+			Vector2(column + 1, row),
+		]
+		for corner: int in CELL_CORNER_ORDER:
+			var sample := corners[corner]
+			vertices.append(sample.position_m)
+			normals.append(sample.normal)
+			colors.append(_sample_data(scan, sample))
+			uvs.append(grid[corner])
 	if vertices.is_empty():
 		return 0
 	var arrays: Array = []
@@ -59,93 +65,21 @@ static func add_row_band(
 	arrays[Mesh.ARRAY_VERTEX] = vertices
 	arrays[Mesh.ARRAY_NORMAL] = normals
 	arrays[Mesh.ARRAY_COLOR] = colors
+	arrays[Mesh.ARRAY_TEX_UV] = uvs
 	mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)
 	mesh.surface_set_material(mesh.get_surface_count() - 1, material)
 	return vertices.size() / 3
 
 
-static func add_grid_band(
-	mesh: ArrayMesh,
-	scan: SonarScan,
-	row: int,
-	material: StandardMaterial3D
-) -> int:
-	var vertices := PackedVector3Array()
-	for column in scan.samples.columns:
-		if column % 6 != 0 and column != scan.samples.columns - 1:
-			continue
-		_append_grid_segment(
-			vertices,
-			scan.samples.sample_at(row - 1, column),
-			scan.samples.sample_at(row, column)
-		)
-	if row == 1 or row % 4 == 0 or row == scan.samples.rows - 1:
-		for column in range(scan.samples.columns - 1):
-			_append_grid_segment(
-				vertices,
-				scan.samples.sample_at(row, column),
-				scan.samples.sample_at(row, column + 1)
-			)
-	if vertices.is_empty():
-		return 0
-	var arrays: Array = []
-	arrays.resize(Mesh.ARRAY_MAX)
-	arrays[Mesh.ARRAY_VERTEX] = vertices
-	mesh.add_surface_from_arrays(Mesh.PRIMITIVE_LINES, arrays)
-	mesh.surface_set_material(mesh.get_surface_count() - 1, material)
-	return vertices.size() / 2
-
-
-static func _append_grid_segment(
-	vertices: PackedVector3Array,
-	a: SonarSample,
-	b: SonarSample
-) -> void:
-	if not a.observed or not b.observed:
-		return
-	vertices.append(a.position_m + a.normal * 0.08)
-	vertices.append(b.position_m + b.normal * 0.08)
-
-
-static func _append_triangle(
-	vertices: PackedVector3Array,
-	normals: PackedVector3Array,
-	colors: PackedColorArray,
-	scan: SonarScan,
-	a: SonarSample,
-	b: SonarSample,
-	c: SonarSample
-) -> void:
-	for sample: SonarSample in [a, b, c]:
-		vertices.append(sample.position_m)
-		normals.append(sample.normal)
-		colors.append(_sample_color(scan, sample))
-
-
-static func _sample_color(scan: SonarScan, sample: SonarSample) -> Color:
-	if sample.material == SonarMaterial.Value.METAL:
-		return COLOR_METAL
-	var height := inverse_lerp(
-		scan.minimum_elevation_m,
-		scan.maximum_elevation_m,
-		sample.elevation_m
-	)
-	var color: Color
-	if height <= 0.28:
-		color = COLOR_DEEP.lerp(COLOR_LOW, height / 0.28)
-	elif height <= 0.52:
-		color = COLOR_LOW.lerp(COLOR_MIDDLE, (height - 0.28) / 0.24)
-	elif height <= 0.76:
-		color = COLOR_MIDDLE.lerp(COLOR_HIGH, (height - 0.52) / 0.24)
-	else:
-		color = COLOR_HIGH.lerp(COLOR_PEAK, (height - 0.76) / 0.24)
-	var light_direction := Vector3(-0.35, 0.82, -0.45).normalized()
-	var slope_light := clampf(sample.normal.dot(light_direction), 0.0, 1.0)
-	var shade := lerpf(0.68, 1.0, slope_light)
-	var lit_color := color.lerp(Color.WHITE, sample.intensity * 0.08)
-	return Color(
-		lit_color.r * shade,
-		lit_color.g * shade,
-		lit_color.b * shade,
-		lit_color.a
+static func _sample_data(scan: SonarScan, sample: SonarSample) -> Color:
+	var height := clampf(
+		inverse_lerp(
+			scan.minimum_elevation_m,
+			scan.maximum_elevation_m,
+			sample.elevation_m
+		),
+		0.0,
+		1.0
 	)
+	var metal := 1.0 if sample.material == SonarMaterial.Value.METAL else 0.0
+	return Color(height, metal, clampf(sample.intensity, 0.0, 1.0))

game/presentation/sonar/sonar_relief_renderer.gd

@@ -5,15 +5,32 @@ const SonarScan = preload("res://game/domain/sonar/sonar_scan.gd")
 const SonarReliefMeshBuilder = preload(
 	"res://game/presentation/sonar/sonar_relief_mesh_builder.gd"
 )
+const SonarReliefStyle = preload("res://game/presentation/sonar/sonar_relief_style.gd")
+
+## Matches the glass of the cockpit sonar monitor (0.690 × 0.434, ratio 1.59).
+const RENDER_SIZE := Vector2i(960, 604)
+## Ground width framed by the orthographic camera, independent of the ratio.
+const VIEW_WIDTH_M := 178.0
+## Table-like oblique view from behind the vehicle. The aim point sits right
+## of the scan axis so the relief leaves the right edge to the height scale.
+const CAMERA_AIM_POINT := Vector3(14.0, -46.0, 50.0)
+const CAMERA_ELEVATION_DEGREES := 44.0
+const CAMERA_DISTANCE_M := 120.0
+const IDLE_PROMPT_SIZE := Vector2(600.0, 64.0)
+## Height scale drawn at the right edge of the screen, in viewport pixels.
+const SCALE_BAR_RECT := Rect2(920.0, 70.0, 12.0, 464.0)
+const SCALE_TICK_COUNT := 3
+const SCALE_LABEL_SIZE := Vector2(112.0, 40.0)
+const SCALE_FONT_SIZE := 34
 
 var _current_mesh_instance: MeshInstance3D
-var _current_grid_instance: MeshInstance3D
 var _previous_mesh_instance: MeshInstance3D
 var _contact_root: Node3D
 var _idle_prompt: Label
-var _current_material: StandardMaterial3D
-var _grid_material: StandardMaterial3D
-var _previous_material: StandardMaterial3D
+var _current_material: ShaderMaterial
+var _previous_material: ShaderMaterial
+var _depth_scale: TextureRect
+var _scale_labels: Array[Label] = []
 var _current_scan_id: StringName = &""
 var _previous_scan_id: StringName = &""
 var _built_current_rows := 0
@@ -22,9 +39,8 @@ var _built_current_grid_segment_count := 0
 
 
 func _ready() -> void:
-	size = Vector2i(960, 540)
+	size = RENDER_SIZE
 	render_target_update_mode = SubViewport.UPDATE_ALWAYS
-	positional_shadow_atlas_size = 1024
 	own_world_3d = true
 	_build_render_world()
 
@@ -41,11 +57,11 @@ func present(
 	if current_scan.scan_id != _current_scan_id:
 		_current_scan_id = current_scan.scan_id
 		_current_mesh_instance.mesh = ArrayMesh.new()
-		_current_grid_instance.mesh = ArrayMesh.new()
 		_built_current_rows = 0
 		_built_current_triangle_count = 0
 		_built_current_grid_segment_count = 0
 		_rebuild_contacts(current_scan)
+		_update_depth_scale(current_scan)
 	_build_current_rows(current_scan, clampi(visible_rows, 0, current_scan.samples.rows))
 	_update_contact_visibility(current_scan, visible_rows)
 
@@ -61,7 +77,7 @@ func present(
 				previous_scan,
 				_previous_material
 			)
-		_previous_material.albedo_color.a = clampf(previous_opacity, 0.0, 1.0)
+		SonarReliefStyle.set_opacity(_previous_material, previous_opacity)
 
 
 func render_texture() -> Texture2D:
@@ -84,6 +100,16 @@ func idle_prompt_visible() -> bool:
 	return _idle_prompt != null and _idle_prompt.visible
 
 
+## Elevation labels of the height scale, top (highest) to bottom; empty until
+## a scan has been presented.
+func depth_scale_texts() -> PackedStringArray:
+	var texts := PackedStringArray()
+	if _depth_scale != null and _depth_scale.visible:
+		for label: Label in _scale_labels:
+			texts.append(label.text)
+	return texts
+
+
 func visible_contact_count() -> int:
 	var count := 0
 	for child: Node in _contact_root.get_children():
@@ -96,24 +122,17 @@ func _build_render_world() -> void:
 	var environment_node := WorldEnvironment.new()
 	var environment := Environment.new()
 	environment.background_mode = Environment.BG_COLOR
-	environment.background_color = Color("020407")
-	environment.ambient_light_source = Environment.AMBIENT_SOURCE_COLOR
-	environment.ambient_light_color = Color(0.18, 0.31, 0.34)
-	environment.ambient_light_energy = 0.42
+	environment.background_color = SonarReliefStyle.COLOR_BACKGROUND
+	environment.ambient_light_source = Environment.AMBIENT_SOURCE_DISABLED
 	environment_node.environment = environment
 	add_child(environment_node)
 
-	_current_material = _relief_material(false)
-	_grid_material = _surface_grid_material()
-	_previous_material = _relief_material(true)
+	_current_material = SonarReliefStyle.relief_material(false)
+	_previous_material = SonarReliefStyle.relief_material(true)
 	_current_mesh_instance = MeshInstance3D.new()
 	_current_mesh_instance.name = "CurrentRelief"
 	_current_mesh_instance.mesh = ArrayMesh.new()
 	add_child(_current_mesh_instance)
-	_current_grid_instance = MeshInstance3D.new()
-	_current_grid_instance.name = "CurrentReliefGrid"
-	_current_grid_instance.mesh = ArrayMesh.new()
-	add_child(_current_grid_instance)
 	_previous_mesh_instance = MeshInstance3D.new()
 	_previous_mesh_instance.name = "PreviousRelief"
 	_previous_mesh_instance.mesh = ArrayMesh.new()
@@ -128,72 +147,88 @@ func _build_render_world() -> void:
 	var camera := Camera3D.new()
 	camera.name = "SonarCamera"
 	camera.projection = Camera3D.PROJECTION_ORTHOGONAL
-	camera.size = 116.0
+	camera.keep_aspect = Camera3D.KEEP_WIDTH
+	camera.size = VIEW_WIDTH_M
 	camera.far = 240.0
-	camera.position = Vector3(0.0, 65.0, -30.0)
+	var elevation := deg_to_rad(CAMERA_ELEVATION_DEGREES)
+	camera.position = CAMERA_AIM_POINT + CAMERA_DISTANCE_M * Vector3(
+		0.0, sin(elevation), -cos(elevation)
+	)
 	add_child(camera)
-	camera.look_at(Vector3(0.0, -38.0, 58.0), Vector3.UP)
+	camera.look_at(CAMERA_AIM_POINT, Vector3.UP)
 	camera.current = true
 
-	var key_light := DirectionalLight3D.new()
-	key_light.rotation_degrees = Vector3(-52.0, -28.0, 0.0)
-	key_light.light_energy = 1.25
-	key_light.shadow_enabled = true
-	add_child(key_light)
-	var fill_light := DirectionalLight3D.new()
-	fill_light.rotation_degrees = Vector3(-28.0, 145.0, 18.0)
-	fill_light.light_energy = 0.38
-	add_child(fill_light)
+	_build_depth_scale()
 	_build_idle_prompt()
 
 
 func _build_idle_prompt() -> void:
 	_idle_prompt = Label.new()
 	_idle_prompt.name = "IdlePrompt"
-	_idle_prompt.position = Vector2(180.0, 238.0)
-	_idle_prompt.size = Vector2(600.0, 64.0)
+	_idle_prompt.position = (Vector2(RENDER_SIZE) - IDLE_PROMPT_SIZE) * 0.5
+	_idle_prompt.size = IDLE_PROMPT_SIZE
 	_idle_prompt.text = "SONAR PRÊT · F POUR ÉMETTRE"
 	_idle_prompt.horizontal_alignment = HORIZONTAL_ALIGNMENT_CENTER
 	_idle_prompt.vertical_alignment = VERTICAL_ALIGNMENT_CENTER
 	_idle_prompt.add_theme_font_size_override("font_size", 26)
-	_idle_prompt.add_theme_color_override("font_color", Color(0.38, 0.88, 0.86))
+	_idle_prompt.add_theme_color_override("font_color", SonarReliefStyle.COLOR_MIDDLE)
 	_idle_prompt.add_theme_color_override("font_outline_color", Color(0.0, 0.04, 0.05))
 	_idle_prompt.add_theme_constant_override("outline_size", 6)
 	add_child(_idle_prompt)
 
 
-func _relief_material(transparent: bool) -> StandardMaterial3D:
-	var material := StandardMaterial3D.new()
-	material.vertex_color_use_as_albedo = true
-	material.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
-	material.cull_mode = BaseMaterial3D.CULL_DISABLED
-	if transparent:
-		material.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
-		material.albedo_color = Color(1.0, 1.0, 1.0, 0.0)
-	return material
+## Height legend: the relief palette is relative to the scan, so the bar shows
+## the real elevations of its two ends and of the steps in between.
+func _build_depth_scale() -> void:
+	var gradient := GradientTexture2D.new()
+	gradient.gradient = SonarReliefStyle.height_gradient()
+	gradient.fill_from = Vector2(0.0, 1.0)
+	gradient.fill_to = Vector2(0.0, 0.0)
+	gradient.width = int(SCALE_BAR_RECT.size.x)
+	gradient.height = int(SCALE_BAR_RECT.size.y)
+	_depth_scale = TextureRect.new()
+	_depth_scale.name = "DepthScale"
+	_depth_scale.texture = gradient
+	_depth_scale.position = SCALE_BAR_RECT.position
+	_depth_scale.size = SCALE_BAR_RECT.size
+	_depth_scale.visible = false
+	add_child(_depth_scale)
+	for tick in SCALE_TICK_COUNT:
+		var label := Label.new()
+		label.size = SCALE_LABEL_SIZE
+		label.position = Vector2(
+			-label.size.x - 8.0,
+			SCALE_BAR_RECT.size.y * tick / float(SCALE_TICK_COUNT - 1) - label.size.y * 0.5
+		)
+		label.horizontal_alignment = HORIZONTAL_ALIGNMENT_RIGHT
+		label.vertical_alignment = VERTICAL_ALIGNMENT_CENTER
+		label.add_theme_font_size_override("font_size", SCALE_FONT_SIZE)
+		label.add_theme_color_override("font_color", SonarReliefStyle.COLOR_MIDDLE)
+		_depth_scale.add_child(label)
+		_scale_labels.append(label)
 
 
-func _surface_grid_material() -> StandardMaterial3D:
-	var material := StandardMaterial3D.new()
-	material.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
-	material.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
-	material.albedo_color = Color(0.32, 0.95, 0.91, 0.34)
-	material.emission_enabled = true
-	material.emission = Color(0.18, 0.78, 0.76)
-	material.emission_energy_multiplier = 1.35
-	return material
+func _update_depth_scale(scan: SonarScan) -> void:
+	for tick in _scale_labels.size():
+		var elevation := lerpf(
+			scan.maximum_elevation_m,
+			scan.minimum_elevation_m,
+			tick / float(_scale_labels.size() - 1)
+		)
+		_scale_labels[tick].text = "%.0f m" % elevation
+	_depth_scale.visible = true
 
 
 func _build_current_rows(scan: SonarScan, visible_rows: int) -> void:
 	var mesh := _current_mesh_instance.mesh as ArrayMesh
-	var grid_mesh := _current_grid_instance.mesh as ArrayMesh
 	while _built_current_rows < visible_rows:
 		if _built_current_rows > 0:
-			_built_current_triangle_count += SonarReliefMeshBuilder.add_row_band(
+			var triangles := SonarReliefMeshBuilder.add_row_band(
 				mesh, scan, _built_current_rows, _current_material
 			)
-			_built_current_grid_segment_count += SonarReliefMeshBuilder.add_grid_band(
-				grid_mesh, scan, _built_current_rows, _grid_material
+			_built_current_triangle_count += triangles
+			_built_current_grid_segment_count += (
+				triangles / 2 * SonarReliefMeshBuilder.GRID_SEGMENTS_PER_CELL
 			)
 		_built_current_rows += 1
 
@@ -210,13 +245,9 @@ func _rebuild_contacts(scan: SonarScan) -> void:
 		marker.position = contact.center_m + Vector3.UP * 1.4
 		marker.visible = false
 		marker.set_meta("forward_distance_m", contact.center_m.z)
-		var material := StandardMaterial3D.new()
-		material.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
-		material.albedo_color = SonarReliefMeshBuilder.COLOR_METAL
-		material.emission_enabled = true
-		material.emission = SonarReliefMeshBuilder.COLOR_METAL
-		material.emission_energy_multiplier = 4.0
-		marker.material_override = material
+		marker.material_override = SonarReliefStyle.marker_material(
+			SonarReliefStyle.COLOR_METAL
+		)
 		_contact_root.add_child(marker)
 
 
@@ -244,11 +275,7 @@ func _add_submarine_marker() -> void:
 	box.size = Vector3(3.2, 1.1, 5.8)
 	marker.mesh = box
 	marker.position = Vector3(0.0, 0.0, 1.0)
-	var material := StandardMaterial3D.new()
-	material.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
-	material.albedo_color = Color.WHITE
-	material.emission_enabled = true
-	material.emission = Color.WHITE
-	material.emission_energy_multiplier = 2.4
-	marker.material_override = material
+	marker.material_override = SonarReliefStyle.marker_material(
+		SonarReliefStyle.COLOR_VEHICLE
+	)
 	add_child(marker)

game/presentation/sonar/sonar_relief_style.gd

@@ -0,0 +1,157 @@
+class_name SonarReliefStyle
+extends RefCounted
+
+## Single owner of the holographic look of the sonar relief: palette, grid
+## spacing, line widths and intensities. Display only: nothing here is a
+## gameplay value.
+
+## Near-black table the hologram floats on. Black also means "unknown".
+const COLOR_BACKGROUND := Color("010507")
+## Height ramp, relative to the scan: dark teal low, cyan mid, pale on peaks.
+const COLOR_DEEP := Color("06404a")
+const COLOR_MIDDLE := Color("17b8c4")
+const COLOR_PEAK := Color("d8fbff")
+## Metal returns keep one warm accent so an anomaly never reads as terrain.
+const COLOR_METAL := Color("ff7a2a")
+const COLOR_VEHICLE := Color("f2ffff")
+
+## Grid lines follow the sample grid: one minor line every N cells.
+const GRID_MINOR_CELLS := 2.0
+const GRID_MAJOR_CELLS := 6.0
+const GRID_MINOR_WIDTH_PX := 1.2
+const GRID_MAJOR_WIDTH_PX := 2.2
+const GRID_MINOR_INTENSITY := 0.30
+const GRID_MAJOR_INTENSITY := 0.80
+## Iso-height contours, in fractions of the scan's height span.
+const CONTOUR_STEP := 0.125
+const CONTOUR_WIDTH_PX := 1.0
+const CONTOUR_INTENSITY := 0.20
+## Translucent surface under the grid and the rim that outlines ridges.
+const SURFACE_INTENSITY := 0.50
+const RIM_INTENSITY := 0.35
+const RIM_POWER := 2.5
+## How much brighter the peaks' lines are than the deep ones.
+const PEAK_LINE_BOOST := 0.55
+
+const _SHADER_CODE := """
+shader_type spatial;
+render_mode unshaded, cull_disabled, depth_draw_always;
+
+uniform vec3 background : source_color;
+uniform vec3 color_deep : source_color;
+uniform vec3 color_middle : source_color;
+uniform vec3 color_peak : source_color;
+uniform vec3 color_metal : source_color;
+uniform float grid_minor_cells;
+uniform float grid_major_cells;
+uniform float grid_minor_width_px;
+uniform float grid_major_width_px;
+uniform float grid_minor_intensity;
+uniform float grid_major_intensity;
+uniform float contour_step;
+uniform float contour_width_px;
+uniform float contour_intensity;
+uniform float surface_intensity;
+uniform float rim_intensity;
+uniform float rim_power;
+uniform float peak_line_boost;
+uniform float opacity = 1.0;
+
+// Anti-aliased line on every multiple of `spacing`, `width_px` wide on screen.
+// Fades out when lines would be closer than a few pixels, so it never shimmers.
+float grid_line(float coordinate, float spacing, float width_px) {
+	float scaled = coordinate / spacing;
+	float pixel = max(fwidth(scaled), 1e-5);
+	float distance_px = abs(fract(scaled - 0.5) - 0.5) / pixel;
+	float line = 1.0 - smoothstep(width_px * 0.5 - 0.5, width_px * 0.5 + 0.5, distance_px);
+	return line * clamp((1.0 / pixel - 2.0) / 3.0, 0.0, 1.0);
+}
+
+void fragment() {
+	// UV carries (column, row) of the sample grid; COLOR.r the relative height,
+	// COLOR.g the metal flag, COLOR.b the echo intensity.
+	float height = clamp(COLOR.r, 0.0, 1.0);
+	vec3 ramp = mix(color_deep, color_middle, smoothstep(0.0, 0.55, height));
+	ramp = mix(ramp, color_peak, smoothstep(0.55, 1.0, height));
+	// The translucent surface stays in the teal-to-cyan range so peaks do not
+	// wash out to grey; only the lines reach the pale peak colour.
+	vec3 fill = mix(color_deep, color_middle, smoothstep(0.0, 0.85, height));
+	float metal = step(0.5, COLOR.g);
+	ramp = mix(ramp, color_metal, metal);
+	fill = mix(fill, color_metal, metal);
+
+	float minor = max(
+		grid_line(UV.x, grid_minor_cells, grid_minor_width_px),
+		grid_line(UV.y, grid_minor_cells, grid_minor_width_px)
+	);
+	float major = max(
+		grid_line(UV.x, grid_major_cells, grid_major_width_px),
+		grid_line(UV.y, grid_major_cells, grid_major_width_px)
+	);
+	float contour = grid_line(height, contour_step, contour_width_px);
+	float rim = pow(1.0 - abs(dot(normalize(NORMAL), normalize(VIEW))), rim_power);
+
+	float lines = max(minor * grid_minor_intensity, major * grid_major_intensity);
+	lines = max(lines, contour * contour_intensity);
+	lines *= 1.0 + peak_line_boost * height;
+	float surface = surface_intensity * (0.22 + 0.78 * height) * (0.8 + 0.2 * COLOR.b);
+	vec3 glow = fill * (surface + rim * rim_intensity) + ramp * lines;
+
+	ALBEDO = background + glow;
+	//FADE ALPHA = opacity;
+}
+"""
+
+static var _opaque_shader: Shader
+static var _fading_shader: Shader
+
+
+## The current scan is opaque: depth-tested, so ridges hide what lies behind
+## them and nothing depends on draw order. The previous scan fades out with the
+## same shader, alpha-blended and still writing depth.
+static func relief_material(fading: bool) -> ShaderMaterial:
+	if _opaque_shader == null:
+		_opaque_shader = Shader.new()
+		_opaque_shader.code = _SHADER_CODE
+		_fading_shader = Shader.new()
+		_fading_shader.code = _SHADER_CODE.replace("//FADE ", "")
+	var material := ShaderMaterial.new()
+	material.shader = _fading_shader if fading else _opaque_shader
+	material.set_shader_parameter("background", COLOR_BACKGROUND)
+	material.set_shader_parameter("color_deep", COLOR_DEEP)
+	material.set_shader_parameter("color_middle", COLOR_MIDDLE)
+	material.set_shader_parameter("color_peak", COLOR_PEAK)
+	material.set_shader_parameter("color_metal", COLOR_METAL)
+	material.set_shader_parameter("grid_minor_cells", GRID_MINOR_CELLS)
+	material.set_shader_parameter("grid_major_cells", GRID_MAJOR_CELLS)
+	material.set_shader_parameter("grid_minor_width_px", GRID_MINOR_WIDTH_PX)
+	material.set_shader_parameter("grid_major_width_px", GRID_MAJOR_WIDTH_PX)
+	material.set_shader_parameter("grid_minor_intensity", GRID_MINOR_INTENSITY)
+	material.set_shader_parameter("grid_major_intensity", GRID_MAJOR_INTENSITY)
+	material.set_shader_parameter("contour_step", CONTOUR_STEP)
+	material.set_shader_parameter("contour_width_px", CONTOUR_WIDTH_PX)
+	material.set_shader_parameter("contour_intensity", CONTOUR_INTENSITY)
+	material.set_shader_parameter("surface_intensity", SURFACE_INTENSITY)
+	material.set_shader_parameter("rim_intensity", RIM_INTENSITY)
+	material.set_shader_parameter("rim_power", RIM_POWER)
+	material.set_shader_parameter("peak_line_boost", PEAK_LINE_BOOST)
+	return material
+
+
+static func set_opacity(material: ShaderMaterial, opacity: float) -> void:
+	material.set_shader_parameter("opacity", clampf(opacity, 0.0, 1.0))
+
+
+static func marker_material(color: Color) -> StandardMaterial3D:
+	var material := StandardMaterial3D.new()
+	material.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
+	material.albedo_color = color
+	return material
+
+
+## Colour of a relative height (0 low, 1 peak), for the depth scale legend.
+static func height_gradient() -> Gradient:
+	var gradient := Gradient.new()
+	gradient.offsets = PackedFloat32Array([0.0, 0.55, 1.0])
+	gradient.colors = PackedColorArray([COLOR_DEEP, COLOR_MIDDLE, COLOR_PEAK])
+	return gradient