message: Added documentation for MatrixMap.
diff: @@ -2331,6 +2331,9 @@ struct PointMatrixHash
  }
  };
  +/** Helper container to keep track of point matrices encountered during
  + * face/edge traversal and to assign unique indices to them.
  + */
  struct MatrixMap
  {
  int GetIndex(const NCMesh::PointMatrix &pm)
  