conversion between tri meshes and poly meshes
To my knowledge, there are no methods to convert back and forth between triangle and polygon meshes.
The conversion from tri mesh to poly mesh should be straightforward as no modifications are required.
The conversion from poly mesh to tri mesh requires to perform some kind of triangulation (i.e.,
PolyConnectivity::triangulate). It will also create some new mesh entities (edges, halfedges) which will have no meaningful property values.