       vec3.copy( this._rootPos, this._bonePos[ 0 ] ); // Save initial position of root for anchoring
    }

    _passFwdBack( chain, debug ){
        const bpos = this._bonePos;
        const cnt  = chain.count;

        // Starting at Effector Bone, loop forward skipping the starting bone
        this._applyDistanceConstraint( chain.links, this._effectorIdx, cnt,  1, 1, cnt ); 

        // Starting at Effector Bone, loop backwards skipping the starting bone
        this._applyDistanceConstraint( chain.lin