The class Surface_mesh_complex_2_in_triangulation_3<Tr> implements a data structure to store the restricted Delaunay triangulation used by the surface mesh generator. The restricted Delaunay triangulation is stored as a two dimensional complex embedded in a three dimensional triangulation.
The class Surface_mesh_complex_2_in_triangulation_3<Tr> is a model of the concept SurfaceMeshComplex_2InTriangulation_3 and can be plugged as the template parameter C2T3 in the function template make_surface_mesh.
The template parameter Tr has to be instantiated with a model of the concept SurfaceMeshTriangulation_3. (Any three dimensional triangulation of CGAL is a model of Triangulation_3 provided that its vertex and cell base class be models of the concept SurfaceMeshVertexBase_3 and SurfaceMeshCellBase_3 respectively.)