Add a 3D ragdoll physics demo

3d/ragdoll_physics/README.md

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+# Ragdoll Physics
+
+This demo includes an example of ragdoll simulation for characters.
+
+The ragdoll setup in this demo was performed by following the [Ragdoll system](https://docs.godotengine.org/en/stable/tutorials/physics/ragdoll_system.html)
+tutorial. The character script also has an `initial_velocity` variable implemented,
+which will give an impulse to all bones part of the ragdoll system.
+This initial impulse is typically used in games to make ragdoll effects more impactful,
+e.g. giving additional recoil after taking a punch.
+
+Impact sounds are played according to the impact speed, and are played with
+reduced pitch when slow motion mode is engaged. This uses
+`AudioServer.playback_speed_scale` which affects all audio,
+so in a more complex project, you would want to use
+[audio buses](https://docs.godotengine.org/en/stable/tutorials/audio/audio_buses.html)
+which can make the effect only apply to certain sounds. This can be used to keep
+music unaffected by the pitch shifting effect.
+
+Character models use outlines provided by the BaseMaterial3D **Stencil > Mode**
+property. The scene's static geometry is designed using CSG nodes and is baked to a
+static mesh and collision to improve load times and allow for global illumination
+with LightmapGI.
+
+Controls:
+
+- <kbd>Space</kbd>: Add a ragdoll at the mouse cursor position
+- <kbd>Shift</kbd> (hold): Enable slow motion mode (1/4 speed)
+- <kbd>R</kbd>: Reset ragdoll simulation and remove user-placed ragdolls
+- <kbd>Right Mouse Button</kbd>: Orbit camera
+- <kbd>Mouse Wheel</kbd>: Zoom
+
+Language: GDScript
+
+Renderer: Forward+
+
+## Screenshots
+
+![Screenshot](screenshots/ragdoll_physics.webp)

3d/ragdoll_physics/characters/mannequiny.LICENSE.md

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+# License for `mannequiny.glb`
+
+Copyright (c) 2020 GDQuest and contributors (https://www.gdquest.com/)
+
+Licensed under CC BY 4.0 International
+
+Downloaded from <https://github.com/gdquest-demos/godot-3d-mannequin/issues/19#issuecomment-582235299>.

3d/ragdoll_physics/characters/mannequiny.glb.import

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+[remap]
+
+importer="scene"
+importer_version=1
+type="PackedScene"
+uid="uid://s42h0rnuf2hf"
+path="res://.godot/imported/mannequiny.glb-c63c284f6fd6b41bb34b1c5bea848ecd.scn"
+
+[deps]
+
+source_file="res://characters/mannequiny.glb"
+dest_files=["res://.godot/imported/mannequiny.glb-c63c284f6fd6b41bb34b1c5bea848ecd.scn"]
+
+[params]
+
+nodes/root_type=""
+nodes/root_name=""
+nodes/root_script=null
+nodes/apply_root_scale=true
+nodes/root_scale=1.0
+nodes/import_as_skeleton_bones=false
+nodes/use_name_suffixes=true
+nodes/use_node_type_suffixes=true
+meshes/ensure_tangents=true
+meshes/generate_lods=true
+meshes/create_shadow_meshes=true
+meshes/light_baking=3
+meshes/lightmap_texel_size=0.2
+meshes/force_disable_compression=false
+skins/use_named_skins=true
+animation/import=true
+animation/fps=30
+animation/trimming=false
+animation/remove_immutable_tracks=true
+animation/import_rest_as_RESET=false
+import_script/path=""
+materials/extract=0
+materials/extract_format=0
+materials/extract_path=""
+_subresources={
+"materials": {
+"Azul_COLOR_0": {
+"use_external/enabled": true,
+"use_external/fallback_path": "res://materials/blue.tres",
+"use_external/path": "uid://ch6ctajgm6nyy"
+},
+"Blanco_COLOR_0": {
+"use_external/enabled": true,
+"use_external/fallback_path": "res://materials/white.tres",
+"use_external/path": "uid://dyij7l6ir0ixa"
+},
+"Negro_COLOR_0": {
+"use_external/enabled": true,
+"use_external/fallback_path": "res://materials/black.tres",
+"use_external/path": "uid://brpxmsr7g2gh6"
+}
+}
+}
+gltf/naming_version=2
+gltf/embedded_image_handling=1

3d/ragdoll_physics/characters/mannequiny_ragdoll.gd

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+extends Node3D
+
+const IMPACT_SOUND_SPEED_SMALL = 0.3
+const IMPACT_SOUND_SPEED_BIG = 1.0
+
+## The velocity to apply on the first physics frame.
+@export var initial_velocity: Vector3
+
+var has_applied_initial_velocity := false
+
+# Used to play an impact sound on sudden velocity changes.
+# We use the pelvis bone as it's close to the center of mass of the character model.
+# For more detailed impact sounds, you could place multiple AudioStreamPlayer nodes as a child
+# of each limb.
+var previous_pelvis_speed := 0.0
+
+@onready var pelvis := $"root/root_001/Skeleton3D/PhysicalBoneSimulator3D/Physical Bone pelvis"
+
+
+func _ready() -> void:
+	$root/root_001/Skeleton3D/PhysicalBoneSimulator3D.physical_bones_start_simulation()
+	if not initial_velocity.is_zero_approx():
+		for physical_bone in $root/root_001/Skeleton3D/PhysicalBoneSimulator3D.get_children():
+			# Give the ragdoll an initial motion by applying velocity on all its bones upon being spawned.
+			physical_bone.apply_central_impulse(initial_velocity)
+
+
+func _physics_process(_delta: float) -> void:
+	var pelvis_speed: float = pelvis.linear_velocity.length()
+	# Ensure the speed used to determine the threshold doesn't change with time scale.
+	var impact_speed := (previous_pelvis_speed - pelvis_speed) / Engine.time_scale
+	if impact_speed > IMPACT_SOUND_SPEED_BIG:
+		$ImpactSoundBig.play()
+	elif impact_speed > IMPACT_SOUND_SPEED_SMALL:
+		$ImpactSoundSmall.play()
+
+	previous_pelvis_speed = pelvis_speed

3d/ragdoll_physics/characters/mannequiny_ragdoll.gd.uid

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+uid://bvbikscp01gbc