Add a 3D sky shaders demo

This uses https://github.com/Rytelier/godot-sky-and-volumetric-clouds
as a base, with several changes made:

- Spheres are now used to represent radiance map reflections of varying
  roughness and metallic values.
- A day/night cycle is now featured.
- Mipmaps are enabled on the weather texture as an optimization.
- The default radiance map settings are more conservative to account
  for the real-time sky shader.
  - This makes reflections lower quality, but it's not too noticeable
    in most real world scenes (especially if using GI techniques for reflections).
- Debanding is now applied in the project settings, rather than on the sky shader.
  This is significantly faster (over 0.1 ms saved on a RX 6900 XT in 3840×2160).
  It also has the benefit of working on materials, which can exhibit banding
  if not textured.
  - The sky shader has debanding commented out in case it's needed.
    This debanding also applies to the lower half of the sky as well in this case,
    as it was required to get rid of noticeable banding on the lower half.
- Cloud coverage and density uniform hints now allow values as low as 0.001.

Co-authored-by: Rytelier <[email protected]>
Co-authored-by: Clay John <[email protected]>

3d/sky_shaders/README.md

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+# 3D Sky Shaders
+
+An example of a sky shader in Godot. This shader features real-time volumetric
+clouds and physical sky with Raleigh and Mie scattering, which causes the sky's
+colors to adjust automatically depending on the sun angle. The sun's angle is set
+automatically from the first DirectionalLight3D node in the scene
+(unless its sky mode is **Light Only**).
+
+Physical sky features are based on the built-in PhysicalSkyMaterial, while
+volumetric clouds were added after converting PhysicalSkyMaterial to a
+ShaderMaterial using the **Convert to ShaderMaterial** button in the editor
+resource dropdown.
+
+> **Warning**
+>
+> Sky shaders are rendered every frame if they use the `TIME` variable or are
+> otherwise updated every frame (e.g. if an uniform is updated in `_process()`
+> or with an AnimationPlayer). This has a significant performance impact for
+> complex sky shaders. The performance impact can be reduced by adjusting the
+> radiance map properties in Environment, but it will remain significant.
+>
+> The shader in this demo project is expensive, and is intended to be used in
+> games where most of the sky remains visible at all times (such as flight
+> simulators).
+>
+> Optimizations to sky shader rendering are planned in future Godot releases.
+
+Language: GDScript
+
+Renderer: Forward Plus
+
+## How does it work?
+
+The day/night cycle is performed using an AnimationPlayer node that adjusts node
+properties and the sky shader parameters in real-time.
+
+Spheres with varying levels of roughness and metallic materials are instanced using
+a [`@tool` script](https://docs.godotengine.org/en/latest/tutorials/plugins/running_code_in_the_editor.html)
+so that they don't have to be created manually in the editor, yet they can still be previewed within the editor.
+
+## Screenshots
+
+![Screenshot](screenshots/sky_shaders.webp)

3d/sky_shaders/default_env.tres

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+[gd_resource type="Environment" load_steps=2 format=2]
+
+[sub_resource type="ProceduralSky" id=1]
+
+[resource]
+background_mode = 2
+sky = SubResource( 1 )

3d/sky_shaders/icon.png.import

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+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://ckaq2n0hvlwq1"
+path="res://.godot/imported/icon.png-487276ed1e3a0c39cad0279d744ee560.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://icon.png"
+dest_files=["res://.godot/imported/icon.png-487276ed1e3a0c39cad0279d744ee560.ctex"]
+
+[params]
+
+compress/mode=0
+compress/high_quality=false
+compress/lossy_quality=0.7
+compress/hdr_compression=1
+compress/normal_map=0
+compress/channel_pack=0
+mipmaps/generate=false
+mipmaps/limit=-1
+roughness/mode=0
+roughness/src_normal=""
+process/fix_alpha_border=true
+process/premult_alpha=false
+process/normal_map_invert_y=false
+process/hdr_as_srgb=false
+process/hdr_clamp_exposure=false
+process/size_limit=0
+detect_3d/compress_to=1

3d/sky_shaders/main.gd

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+extends Node3D
+
+var base_height = ProjectSettings.get_setting("display/window/size/viewport_height")
+
+# The camera field of view to smoothly interpolate to.
+@onready var desired_fov = $YawCamera/Camera3D.fov
+
+func _ready():
+	Input.mouse_mode = Input.MOUSE_MODE_CAPTURED
+
+
+func _process(_delta):
+	# Make the slider follow the day/night cycle.
+	$Panel/MarginContainer/VBoxContainer/TimeOfDay/HSlider.value = $AnimationPlayer.current_animation_position
+	$WorldEnvironment.environment.sky.sky_material.set_shader_parameter("cloud_time_offset", $AnimationPlayer.current_animation_position)
+
+	$YawCamera/Camera3D.fov = lerpf($YawCamera/Camera3D.fov, desired_fov, 0.2)
+
+
+
+func _input(event):
+	if event.is_action_pressed("toggle_gui"):
+		$Panel.visible = not $Panel.visible
+		$Help.visible = not $Help.visible
+
+	if event.is_action_pressed("toggle_spheres"):
+		$Spheres.visible = not $Spheres.visible
+
+	if event.is_action_pressed("toggle_mouse_capture"):
+		if Input.mouse_mode == Input.MOUSE_MODE_CAPTURED:
+			Input.mouse_mode = Input.MOUSE_MODE_VISIBLE
+		else:
+			Input.mouse_mode = Input.MOUSE_MODE_CAPTURED
+
+	if Input.mouse_mode == Input.MOUSE_MODE_CAPTURED and event is InputEventMouseMotion:
+		# Mouselook.
+		# Compensate motion speed to be resolution-independent (based on the window height).
+		var relative_motion = event.relative * DisplayServer.window_get_size().y / base_height
+		$YawCamera.rotation.x += relative_motion.y * 0.001
+		$YawCamera.rotation.y += relative_motion.x * 0.001
+
+	# Mouse wheel currently doesn't work in input actions. Hardcode mouse wheel as a workaround.
+	if event.is_action_pressed("increase_camera_fov") or Input.is_mouse_button_pressed(MOUSE_BUTTON_WHEEL_DOWN):
+		desired_fov = clampf(desired_fov + 5.0, 20.0, 150.0)
+	if event.is_action_pressed("decrease_camera_fov") or Input.is_mouse_button_pressed(MOUSE_BUTTON_WHEEL_UP):
+		desired_fov = clampf(desired_fov - 5.0, 20.0, 150.0)
+
+
+func _on_time_of_day_value_changed(value):
+	# Update time of day.
+	$AnimationPlayer.seek(value)
+	# TODO: Display HH:MM time.
+	$Panel/MarginContainer/VBoxContainer/TimeOfDay/Value.text = str(value).pad_decimals(2)
+
+
+func _on_speed_minus_pressed():
+	# Allow minimum value to be zero so that the special case can be reached for pausing.
+	$AnimationPlayer.speed_scale = clampf($AnimationPlayer.speed_scale * 0.5, 0.0, 12.8)
+	if $AnimationPlayer.speed_scale < 0.0499:
+		# Going below 0.5× speed; pause.
+		$AnimationPlayer.speed_scale = 0.0
+
+	update_speed_label()
+
+
+func _on_speed_plus_pressed():
+	$AnimationPlayer.speed_scale = clampf($AnimationPlayer.speed_scale * 2.0, 0.05, 12.8)
+	if is_zero_approx($AnimationPlayer.speed_scale):
+		# Currently paused; resume playback.
+		$AnimationPlayer.speed_scale = 0.1
+
+	update_speed_label()
+
+
+func update_speed_label():
+	# The default speed scale for this AnimationPlayer is internally 0.1, so multiply the displayed value by 10.
+	if is_zero_approx($AnimationPlayer.speed_scale):
+		$Panel/MarginContainer/VBoxContainer/TimeOfDay/CurrentSpeed.text = "Pause"
+	else:
+		$Panel/MarginContainer/VBoxContainer/TimeOfDay/CurrentSpeed.text = "%.2f×" % ($AnimationPlayer.speed_scale * 10)
+
+
+func _on_cloud_coverage_value_changed(value):
+	$WorldEnvironment.environment.sky.sky_material.set_shader_parameter("cloud_coverage", value)
+	$Panel/MarginContainer/VBoxContainer/Clouds/CoverageValue.text = "%d%%" % (value * 100)
+
+
+func _on_cloud_density_value_changed(value):
+	$WorldEnvironment.environment.sky.sky_material.set_shader_parameter("cloud_density", value)
+	$Panel/MarginContainer/VBoxContainer/Clouds/DensityValue.text = "%d%%" % (value * 100)
+
+
+func _on_process_mode_item_selected(index):
+	match index:
+		0:
+			$WorldEnvironment.environment.sky.process_mode = Sky.PROCESS_MODE_QUALITY
+			$Panel/MarginContainer/VBoxContainer/RadianceSize.visible = true
+			# Reset radiance size as the engine forces radiance size to 256 after switching to the Real-Time process mode.
+			_on_radiance_size_item_selected($Panel/MarginContainer/VBoxContainer/RadianceSize/OptionButton.selected)
+		1:
+			$WorldEnvironment.environment.sky.process_mode = Sky.PROCESS_MODE_INCREMENTAL
+			$Panel/MarginContainer/VBoxContainer/RadianceSize.visible = true
+			# Reset radiance size as the engine forces radiance size to 256 after switching to the Real-Time process mode.
+			_on_radiance_size_item_selected($Panel/MarginContainer/VBoxContainer/RadianceSize/OptionButton.selected)
+		2:
+			$WorldEnvironment.environment.sky.process_mode = Sky.PROCESS_MODE_REALTIME
+			# Radiance size is forced to 256 by the engine when using Real-Time process mode.
+			$Panel/MarginContainer/VBoxContainer/RadianceSize.visible = false
+
+
+func _on_radiance_size_item_selected(index):
+	match index:
+		0:
+			$WorldEnvironment.environment.sky.radiance_size = Sky.RADIANCE_SIZE_32
+		1:
+			$WorldEnvironment.environment.sky.radiance_size = Sky.RADIANCE_SIZE_64
+		2:
+			$WorldEnvironment.environment.sky.radiance_size = Sky.RADIANCE_SIZE_128
+		3:
+			$WorldEnvironment.environment.sky.radiance_size = Sky.RADIANCE_SIZE_256
+		4:
+			$WorldEnvironment.environment.sky.radiance_size = Sky.RADIANCE_SIZE_512

3d/sky_shaders/perlworlnoise.png.import

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+[remap]
+
+importer="3d_texture"
+type="CompressedTexture3D"
+uid="uid://48aujjq3b6pj"
+path="res://.godot/imported/perlworlnoise.png-3a040af7870a245e2e85a129517a2537.ctex3d"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://perlworlnoise.png"
+dest_files=["res://.godot/imported/perlworlnoise.png-3a040af7870a245e2e85a129517a2537.ctex3d"]
+
+[params]
+
+compress/mode=0
+compress/high_quality=false
+compress/lossy_quality=0.7
+compress/hdr_compression=1
+compress/channel_pack=0
+mipmaps/generate=true
+mipmaps/limit=-1
+slices/horizontal=128
+slices/vertical=1

3d/sky_shaders/project.godot

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+; Engine configuration file.
+; It's best edited using the editor UI and not directly,
+; since the parameters that go here are not all obvious.
+;
+; Format:
+;   [section] ; section goes between []
+;   param=value ; assign values to parameters
+
+config_version=5
+
+[application]
+
+config/name="3D Sky Shaders"
+config/description="A short educational sample showing one way of using sky shaders to render real time volumetric cloudscapes."
+run/main_scene="res://Main.tscn"
+config/features=PackedStringArray("4.0")
+config/icon="res://icon.png"
+
+[display]
+
+window/stretch/mode="canvas_items"
+window/stretch/aspect="expand"
+window/vsync/use_vsync=false
+
+[input]
+
+toggle_mouse_capture={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":4194305,"key_label":0,"unicode":0,"echo":false,"script":null)
+, Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":4194341,"key_label":0,"unicode":0,"echo":false,"script":null)
+]
+}
+toggle_gui={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":4194332,"key_label":0,"unicode":0,"echo":false,"script":null)
+]
+}
+toggle_spheres={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":4194333,"key_label":0,"unicode":0,"echo":false,"script":null)
+]
+}
+increase_camera_fov={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":4194322,"key_label":0,"unicode":0,"echo":false,"script":null)
+]
+}
+decrease_camera_fov={
+"deadzone": 0.5,
+"events": [Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"window_id":0,"alt_pressed":false,"shift_pressed":false,"ctrl_pressed":false,"meta_pressed":false,"pressed":false,"keycode":0,"physical_keycode":4194320,"key_label":0,"unicode":0,"echo":false,"script":null)
+]
+}
+
+[rendering]
+
+anti_aliasing/quality/msaa_3d=2
+anti_aliasing/quality/use_debanding=true
+vram_compression/import_etc2=false