applyMatrix4 method
Applies matrix m to every Vector3 element of this
BufferAttribute.
Implementation
void applyMatrix4(Matrix4 m) {
  for (int i = 0, l = count; i < l; i++) {
    _vector.fromBuffer( this, i );
    _vector.applyMatrix4(m);
    setXYZ(i, _vector.x, _vector.y, _vector.z);
  }
}