# [name]

A solver for IK with `CCD Algorithm`.
[name] solves Inverse Kinematics Problem with CCD Algorithm. [name] is designed to work with [page:SkinnedMesh] but also can be used with [page:MMDLoader] or [page:GLTFLoader] skeleton.

## Import

[name] is an add-on, and must be imported explicitly. See [link:#manual/introduction/Installation Installation / Addons].

`import { CCDIKSolver } from 'three/addons/animation/CCDIKSolver.js';`

## Code Example

`let ikSolver; // // Bones hierarchy: // // root // ├── bone0 // │ └── bone1 // │ └── bone2 // │ └── bone3 // └── target // // Positioned as follow on the cylinder: // // o <- target (y = 20) // // +----o----+ <- bone3 (y = 12) // | | // | o | <- bone2 (y = 4) // | | // | o | <- bone1 (y = -4) // | | // +----oo---+ <- root, bone0 (y = -12) // let bones = [] // "root" let rootBone = new Bone(); rootBone.position.y = -12; bones.push( rootBone ); // "bone0" let prevBone = new Bone(); prevBone.position.y = 0; rootBone.add( prevBone ); bones.push( prevBone ); // "bone1", "bone2", "bone3" for ( let i = 1; i <= 3; i ++ ) { const bone = new Bone(); bone.position.y = 8; bones.push( bone ); prevBone.add( bone ); prevBone = bone; } // "target" const targetBone = new Bone(); targetBone.position.y = 24 + 8 rootBone.add( targetBone ); bones.push( targetBone ); // // skinned mesh // const mesh = new SkinnedMesh( geometry, material ); const skeleton = new Skeleton( bones ); mesh.add( bones[ 0 ] ); // "root" bone mesh.bind( skeleton ); // // ikSolver // const iks = [ { target: 5, // "target" effector: 4, // "bone3" links: [ { index: 3 }, { index: 2 }, { index: 1 } ] // "bone2", "bone1", "bone0" } ]; ikSolver = new CCDIKSolver( mesh, iks ); function render() { ikSolver?.update(); renderer.render( scene, camera ); }`

## Examples

[example:webgl_animation_skinning_ik]
[example:webgl_loader_mmd]
[example:webgl_loader_mmd_pose]
[example:webgl_loader_mmd_audio]

## Constructor

### [name]( [param:SkinnedMesh mesh], [param:Array iks] )

[page:SkinnedMesh mesh] — [page:SkinnedMesh] for which [name] solves IK problem.
[page:Array iks] — An array of [page:Object] specifying IK parameter. target, effector, and link-index are index integers in .skeleton.bones. The bones relation should be "links[ n ], links[ n - 1 ], ..., links[ 0 ], effector" in order from parent to child.

- [page:Integer target] — Target bone.
- [page:Integer effector] — Effector bone.
- [page:Array links] — An array of [page:Object] specifying link bones.
  - [page:Integer index] — Link bone.
  - [page:Vector3 limitation] — (optional) Rotation axis. Default is undefined.
  - [page:Vector3 rotationMin] — (optional) Rotation minimum limit. Default is undefined.
  - [page:Vector3 rotationMax] — (optional) Rotation maximum limit. Default is undefined.
  - [page:Boolean enabled] — (optional) Default is true.
- [page:Integer iteration] — (optional) Iteration number of calculation. Smaller is faster but less precise. Default is 1.
- [page:Number minAngle] — (optional) Minimum rotation angle in a step. Default is undefined.
- [page:Number maxAngle] — (optional) Maximum rotation angle in a step. Default is undefined.

Creates a new [name].

## Properties

### [property:Array iks]

An array of IK parameter passed to the constructor.

### [property:SkinnedMesh mesh]

[page:SkinnedMesh] passed to the constructor.

## Methods

### [method:CCDIKHelper createHelper]()

Return [page:CCDIKHelper]. You can visualize IK bones by adding the helper to scene.

### [method:this update]()

Update IK bones quaternion by solving CCD algorithm.

### [method:this updateOne]( [param:Object ikParam] )

Update an IK bone quaternion by solving CCD algorithm.

## Source

[link:https://github.com/mrdoob/three.js/blob/master/examples/jsm/animation/CCDIKSolver.js examples/jsm/animation/CCDIKSolver.js]