BoneIK

Inverse Kinematic addon for Godot.

Here is a short video (without sound) showing how to use 3 of the inverse kinematics.

Main differences between Godot IK and this addon are:

1. There is no Node like Skeleton2D to handle all bones.
   • Why? I don't know... My plan is to wait the "need" for it.
2. Inverse kinematics are not Resource, there is a Node for each IK.

Installation

• Download latest release
• Extract addons directory from ZIP
• Move addons directory to your project directory
  • If your project already have an addons directory, copy addons/bone_ik to your project addons
• Open Godot project
• Go to Project > Project Settings... > Plugins
  • You should be seeing BoneIk plugin there, otherwise something was done wrong
• Check Enable in BoneIK plugin
• Restart Godot

Good and Bad

Good:

• Scaling only one of the axis negatively works

Bad:

• Probably slower than Godot IK
  • Written in GDScript
  • Create Polygon2D to represent bone shapes
• Only contains logic of
  • SkeletonModification2DLookAt
  • SkeletonModification2DTwoBonesIK
  • SkeletonModification2DCCDIK
  • SkeletonModification2DFABRIK
• No integration with Godot default nodes
  • Can't add skeleton to Polygon2D.skeleton

Why

(11-dez-2023) After a long time reading Godot inverse kinematic and trying to fix (#83397, #83330, #81544, #81051, #81048), I started questioning myself if my changes were correct (comment).

So I started rewriting in GDScript to get a better knowledge of the logic! The difference is that I'm copying logic that makes sense to me and removing anything that I don't understand why exists (and writing my own logic).

This could be a bad decision, but rewriting will give me a better idea of the problems and solutions that others had.

Credits

• Godot.
• TwistedTwigleg for writing IK for Godot.
• Alan Zucconi for explaining Two Bones IK.
• Ryan Jucket for explaining CCDIK.
• Sean for explaining FABRIK.