Module bone_rigger 

Bone Rigger — click-to-place bone anchors on the SDF surface and define joint hierarchies for skeletal animation.

Overview

The rigger owns a BoneSkeleton — a flat list of BoneDesc values wired into a tree through parent–child relationships. Each bone has:

• a head and tail in object space (placed by clicking on the SDF surface)
• a roll angle around the bone’s Y axis
• optional weight envelope (capsule) parameters that control how much each surface particle is influenced by this bone
• FK and IK flags

Interaction flow

1. User enters PlacingHead mode; clicks on the SDF surface → sets head.
2. User clicks again → sets tail, finalises bone and enters Idle.
3. With a bone selected, user can parent it to another bone.
4. BoneSkeleton::bind_weights computes per-particle skinning weights from the envelope capsules using a dual-quaternion weighting scheme.

IK chains

IkChain represents a chain of bones from a root to an effector tip. IkChain::solve_ccd runs the Cyclic Coordinate Descent algorithm for n iterations, pulling the tip toward the target.

Structs

BoneConstraint

Rotation limits for a joint.

BoneDesc

Descriptor for a single bone in the skeleton.

BoneId

BoneRigger

Full bone rigging tool state.

BoneSkeleton

The full skeleton — flat map of bones plus hierarchy helpers.

IkChain

A chain of bone IDs from root to tip used for IK solving.

SkinWeight

Up to 4 bone influences per surface point.

Enums

BoneRole

Semantic role of a bone, used by the auto-rigger.

RiggerMode