code: public void     getLocalPosition(int boneindex, Vector3f pos)
      {
          pos.x = mBones[boneindex].LocalMatrix.m30();
          pos.y = mBones[boneindex].LocalMatrix.m31();
          pos.z = mBones[boneindex].LocalMatrix.m32();
      }
docs: Gets the local position (relative to the parent) of a bone.
  <p>
  All bones in the skeleton start out at the origin oriented along the bone axis (usually 0,0,1).
  The pose orients and positions each bone in the skeleton with respect to this initial state.
  The local bone matrix expresses the orientation and position of the bone relative
  to it's parent. This function returns the translation component of that matrix.
  @param boneindex	zero based index of bone whose position is wanted.
  @return local translation for the designated bone.
  
  @see #setLocalRotation
  @see #setWorldRotations
  @see #setWorldMatrix
  @see GVRSkeleton#setBoneAxis