@modoki/engine / index / BoneAttachment

Variable: BoneAttachment

const BoneAttachment: Trait<{ bone: string; target: string; }>

BoneAttachment — pin this entity to a bone of a SkinnedModel's skeleton (an Unreal-style socket). Put it on a normal entity that also has a Renderable3D/Renderable3DPrimitive + Transform: a weapon in the hand, a VFX on a joint, a hat on the head.

Each frame the render sync finds bone in target's animated skeleton and drives this entity to follow the bone's world POSITION + ROTATION, so it tracks the animation. The entity's own Transform seats the prop: position is a world-unit offset rotated into the bone's orientation, rotation composes onto the bone's, and SCALE is the prop's own world scale (NOT inherited from the rig — so a prop stays its authored size even on a heavily-scaled model).

Cheap by design: O(attachments), not O(bones) — the bones themselves stay plain Three objects, never ECS entities.

• target — GUID of the entity carrying the SkinnedModel.
• bone — bone name as authored in the GLB skeleton (see getBoneNames).