private void OnAddRigBuilderCallback(RigBuilder rigBuilder)
        {
            if (m_RigBuilder != rigBuilder)
            {
                return;
            }

            if (m_RigBuilder.graph.IsValid())
            {
                m_RigBuilder.Clear();
                SetBaseTransform(); //before RigBuilder.Build
                m_RigBuilder.Build();
            }
        }