WiggleBone Skeleton Modifier for Godot Engine 4.3

Adds jiggle physics to a Skeleton3D bone using SkeletonModifier3D nodes.

Note

Requires Godot 4.3. As Godot 4.2 and lower does not support SkeletonModifier3D nodes, the branch godot-4.2 has an alternative implementation using Node3D and can be used as a fallback for existing projects.

• Installation
• Usage
• Wiggle rotation
• Wiggle position
• Testing in editor
• References

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Installation

1. Search for wigglebone in the AssetLib editor tab
2. Download and install the plugin
3. Enable the plugin in the project settings via the Plugins tab

or...

1. Clone this repository or download the archive
2. Copy the folder addons/wigglebone to your project's addons folder (create it if needed)
3. Enable the plugin in the project settings via the Plugins tab

Usage

You can now add DMWBWiggleRotationModifier3D or DMWBWigglePositionModifier3D nodes to a Skeleton3D. See the example scenes in examples.

Note: Poses modified in SkeletonModifier3D nodes are only temporary for the current frame. Modifiers for parent bones should come first (above) in the scene tree, otherwise it may have not the desired effect.

Warning

The WiggleBone node is deprecated and should be replaced with either DMWBWiggleRotationModifier3D or DMWBWigglePositionModifier3D.

Wiggle rotation

DMWBWiggleRotationModifier3D

Rotates the bone around the current bone pose. The current pose direction acts as the spring's rest position.

Modifier properties

Property	Description
properties	Properties used to move the bone. (DMWBWiggleRotationProperties3D)
force_global	Applies a constant global force.
force_local	Applies a constant force relative to the bone's pose.
handle_distance	Sets the distance of the editor handle on the bone's Y axis.

Property resource

DMWBWiggleRotationProperties3D

Used to set the modifier properties. Can be shared by multiple modifiers.

Property	Description
spring_freq	The spring's oscillation frequency. Note: Adding forces may change the frequency.
angular_damp	Damping factor of the angular velocity.
force_scale	Defines how much the rotation is influenced by forces.
linear_scale	Defines how much the rotation is influenced by global movement.
swing_span	Maximum angle the bone can rotate around its pose.
gravity	Applies a constant global force.

Methods

Method	Description
void reset()	Reset rotation and angular velocity.
void add_torque_impulse(torque: Vector3)	Add a global torque impulse.
void add_force_impulse(force: Vector3)	Add a global force impulse.

Free rotation

To allow the bone to rotate freely, the spring frequency (spring_freq) can be set to 0.0 or a very low value.

Limitations

• Rotations near 180° have a "pole", which means that the bone spins around its forward axis near that limit.
• Rotation with exactly 180° have no unique solution and the bone's forward axis rotation snaps to a fallback axis.
• When the rotation approaches 180° while using a low spring frequency, the angular rotation may change its direction in certain cases.

Note: Some of these problems can be avoided by setting the bone pose rotation already to the desired rest position. For example, if a bone is hanging down, the bone pose should already be pointing down.

Wiggle position

DMWBWigglePositionModifier3D

Moves the bone around the current bone pose without rotating. The current pose position acts as the spring's rest position.

Modifier properties

Property	Description
properties	Properties used to move the bone. (DMWBWigglePositionProperties3D)
force_global	Applies a constant global force.
force_local	Applies a constant local force relative to the bone's pose.

Property resource

DMWBWigglePositionProperties3D

Used to set the modifier properties. Can be shared by multiple modifiers.

Property	Description
spring_freq	The spring's oscillation frequency. Note: Adding forces may change the frequency.
linear_damp	Damping factor of the velocity.
force_scale	Defines how much the position is influenced by forces.
linear_scale	Defines how much the position is influenced by global movement.
max_distance	Maximum distance the bone can move around its pose position.
gravity	Applies a constant global force.

Methods

Method	Description
void reset()	Reset position and velocity.
void add_force_impulse(force: Vector3)	Add a global force impulse.

Testing in Editor

When a DMWBWiggleRotationModifier3D or DMWBWigglePositionModifier3D node is selected in the scene tree, a force can be applied to it by dragging its handle. Another way is to drag or rotate the Skeleton3D or one of its parents.

Disabling Editor Gizmo

The editor gizmo (cone/sphere) can be hidden in the 3D viewport by disabling it in View > Gizmos > DMWBWiggleRotationModifier3D or View > Gizmos > DMWBWigglePositionModifier3D, respectively.

References

Springs

Based on Springs: From Hooke's law to a time based equation by EgoMooses
https://www.youtube.com/watch?v=FZekwtIO0I4

Time-independent lerp

Lerp smoothing is broken by Freya Holmér
https://www.youtube.com/watch?v=LSNQuFEDOyQ