How to use A3DMatrix4x4 acquired by Exchange in HoopsCommunicator's authoring library?

The matrix used by Exchange(A3DMatrix4x4) or Communicator is a 4 by 4 matrix, but the SC::Store::Matrix3d used by the Communicator authoring library is a 3 by 3 matrix, how can this be converted to each other, and I want to use the authoring library to associate the assembly stream cache object.