Add a 3D antialiasing demo

3d/antialiasing/README.md

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+# 3D Anti-Aliasing
+
+This project showcases the various 3D antialiasing techniques supported by Godot.
+
+- **Multisample antialiasing (MSAA):** High quality, high performance cost.
+  Does not blur the image.
+  - Does not affect shader-induced aliasing (such as specular aliasing) or alpha
+	scissor materials, so these will remain aliased.
+- **Fast approximate antialiasing (FXAA):** Medium quality, low performance cost.
+  Slightly blurs the image.
+- **Temporal antialiasing (TAA):** High-quality, low performance cost. Slightly
+  blurs the image (but less so than FXAA).
+  - Antialiasing quality is worse on fast-moving objects than other methods,
+	especially at lower framerates since the TAA won't have enough time to
+	converge on those objects.
+  - Can introduce ghosting artifacts on moving objects, especially if motion
+	vectors are not correctly generated from a given material shader.
+- **Supersampling (SSAA):** The highest-quality technique, but also the most
+  expensive. Does not blur the image.
+  - 200% resolution scale is equivalent to 4× SSAA, as each dimension is
+	doubled. For example, if running in a 1920×1080 window at 200% render scale,
+	the 3D framebuffer will be 3840×2160.
+  - SSAA can be used together with FXAA or TAA to counter the blurring added by
+	those algorithms, while further improving antialiasing quality.
+
+Godot allows using multiple antialiasing techniques at the same time. This can
+be useful to obtain the best possible quality, or to find a better performance
+tradeoff.
+
+Language: GDScript
+
+Renderer: Vulkan Clustered
+
+## Screenshots
+
+![Screenshot](screenshots/3d_anti_aliasing.png)
+
+## Licenses
+
+Files in the `polyhaven/` folder are downloaded from <https://polyhaven.com/a/dutch_ship_medium>
+and are licensed under CC0 1.0 Universal.

3d/antialiasing/anti_aliasing.gd

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+extends Node
+
+const ROT_SPEED = 0.003
+const ZOOM_SPEED = 0.125
+const MAIN_BUTTONS = MOUSE_BUTTON_MASK_LEFT | MOUSE_BUTTON_MASK_RIGHT | MOUSE_BUTTON_MASK_MIDDLE
+
+var tester_index = 0
+var rot_x = -TAU / 16  # This must be kept in sync with RotationX.
+var rot_y = TAU / 8  # This must be kept in sync with CameraHolder.
+var camera_distance = 2.0
+var base_height = ProjectSettings.get_setting("display/window/size/viewport_height")
+
+@onready var testers = $Testers
+@onready var camera_holder = $CameraHolder # Has a position and rotates on Y.
+@onready var rotation_x = $CameraHolder/RotationX
+@onready var camera = $CameraHolder/RotationX/Camera3D
+
+
+func _ready():
+	camera_holder.transform.basis = Basis.from_euler(Vector3(0, rot_y, 0))
+	rotation_x.transform.basis = Basis.from_euler(Vector3(rot_x, 0, 0))
+	update_gui()
+
+
+func _unhandled_input(event):
+	if event.is_action_pressed("ui_left"):
+		_on_previous_pressed()
+	if event.is_action_pressed("ui_right"):
+		_on_next_pressed()
+
+	if event is InputEventMouseButton:
+		if event.button_index == MOUSE_BUTTON_WHEEL_UP:
+			camera_distance -= ZOOM_SPEED
+		if event.button_index == MOUSE_BUTTON_WHEEL_DOWN:
+			camera_distance += ZOOM_SPEED
+		camera_distance = clamp(camera_distance, 1.5, 6)
+
+	if event is InputEventMouseMotion and event.button_mask & MAIN_BUTTONS:
+		# Compensate motion speed to be resolution-independent (based on the window height).
+		var relative_motion = event.relative * DisplayServer.window_get_size().y / base_height
+		rot_y -= relative_motion.x * ROT_SPEED
+		rot_x -= relative_motion.y * ROT_SPEED
+		rot_x = clamp(rot_x, -1.57, 0)
+		camera_holder.transform.basis = Basis.from_euler(Vector3(0, rot_y, 0))
+		rotation_x.transform.basis = Basis.from_euler(Vector3(rot_x, 0, 0))
+
+
+func _process(delta):
+	var current_tester = testers.get_child(tester_index)
+	# This code assumes CameraHolder's X and Y coordinates are already correct.
+	var current_position = camera_holder.global_transform.origin.z
+	var target_position = current_tester.global_transform.origin.z
+	camera_holder.global_transform.origin.z = lerp(current_position, target_position, 3 * delta)
+	camera.position.z = lerp(camera.position.z, camera_distance, 10 * delta)
+
+
+func _on_previous_pressed():
+	tester_index = max(0, tester_index - 1)
+	update_gui()
+
+
+func _on_next_pressed():
+	tester_index = min(tester_index + 1, testers.get_child_count() - 1)
+	update_gui()
+
+
+func update_gui():
+	$TestName.text = str(testers.get_child(tester_index).name).capitalize()
+	$Previous.disabled = tester_index == 0
+	$Next.disabled = tester_index == testers.get_child_count() - 1
+
+
+func _on_fxaa_toggled(button_pressed):
+	get_viewport().screen_space_aa = Viewport.SCREEN_SPACE_AA_FXAA if button_pressed else Viewport.SCREEN_SPACE_AA_DISABLED
+
+
+func _on_temporal_antialiasing_toggled(button_pressed):
+	get_viewport().use_taa = button_pressed
+
+
+func _on_msaa_item_selected(index):
+	get_viewport().msaa = index
+
+
+func _on_render_scale_item_selected(index):
+	match index:
+		0:
+			get_viewport().scaling_3d_scale = 0.5
+		1:
+			get_viewport().scaling_3d_scale = 0.75
+		2:
+			get_viewport().scaling_3d_scale = 1.0
+		3:
+			get_viewport().scaling_3d_scale = 1.25
+		4:
+			get_viewport().scaling_3d_scale = 1.5
+		5:
+			get_viewport().scaling_3d_scale = 1.75
+		6:
+			get_viewport().scaling_3d_scale = 2.0