CGAL detect_features() creates unprotectable features - mesh

Question

Based on this example (Remeshing a Polyhedral Domain with Surfaces in the 3D Mesh Generation Manual), I want to mesh a cube-shaped domain with its midplane protected (see the code below). However, make_mesh_3 throws an assertion violation:
CGAL ERROR: assertion violation!
Expr: minimal_size_ > 0 || sq_d > 0
Nevermind the triviality of the example, it's just to show the problem. Based on this discussion, I think the issue is that detect_features creates polylines that intersect each other (perimeter of the midplane intersects the cube edges, and both are added as features).
Are intersecting polyhedra not allowed in the meshdomain? If so, is there a way to access and manipulate the results of detect_features to process conflicting features? I'm trying to figure out how polylines are stored in the mesh domain, but I'm getting nowhere.
Cube with Midplane
// --- External Includes ---
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Mesh_polyhedron_3.h>
#include <CGAL/Polyhedral_mesh_domain_with_features_3.h>
#include <CGAL/Mesh_triangulation_3.h>
#include <CGAL/Mesh_complex_3_in_triangulation_3.h>
#include <CGAL/Mesh_criteria_3.h>
#include <CGAL/make_mesh_3.h>
// CGAL types
namespace cgal {
using Kernel = CGAL::Exact_predicates_inexact_constructions_kernel;
using ConcurrencyTag = CGAL::Sequential_tag;
using PolyhedronSurface = CGAL::Mesh_polyhedron_3<Kernel>::type;
using MeshDomain = CGAL::Polyhedral_mesh_domain_with_features_3<Kernel>;
using Tr = CGAL::Mesh_triangulation_3<MeshDomain,CGAL::Default,ConcurrencyTag>::type;
using Triangulation = CGAL::Mesh_complex_3_in_triangulation_3<Tr>;
using MeshCriteria = CGAL::Mesh_criteria_3<Tr>;
using Point = cgal::MeshDomain::Point_3;
}
int main()
{
// Define points for the cube and midPlane
std::vector<cgal::Point> points =
{
cgal::Point( 1.0, 0.0, 0.0),
cgal::Point( 1.0, 1.0, 0.0),
cgal::Point( 0.0, 1.0, 0.0),
cgal::Point( 0.0, 0.0, 0.0),
cgal::Point( 1.0, 0.0, 1.0),
cgal::Point( 1.0, 1.0, 1.0),
cgal::Point( 0.0, 1.0, 1.0),
cgal::Point( 0.0, 0.0, 1.0),
cgal::Point( 1.0, 0.0, 0.5),
cgal::Point( 1.0, 1.0, 0.5),
cgal::Point( 0.0, 1.0, 0.5),
cgal::Point( 0.0, 0.0, 0.5)
};
// Create polyhedra
cgal::PolyhedronSurface cube, midPlane;
cube.make_triangle( points[0], points[3], points[1]);
cube.make_triangle( points[1], points[3], points[2]);
cube.make_triangle( points[4], points[5], points[7]);
cube.make_triangle( points[5], points[6], points[7]);
cube.make_triangle( points[0], points[4], points[3]);
cube.make_triangle( points[3], points[4], points[7]);
cube.make_triangle( points[1], points[2], points[5]);
cube.make_triangle( points[2], points[6], points[5]);
cube.make_triangle( points[2], points[3], points[6]);
cube.make_triangle( points[3], points[7], points[6]);
cube.make_triangle( points[0], points[1], points[5]);
cube.make_triangle( points[0], points[5], points[4]);
midPlane.make_triangle( points[8], points[9], points[10]);
midPlane.make_triangle( points[8], points[10], points[11]);
// Triangulation
cgal::MeshDomain meshDomain( midPlane, cube );
meshDomain.detect_features();
cgal::MeshCriteria meshCriteria( CGAL::parameters::facet_angle = 30,
CGAL::parameters::edge_size = 0.2 );
auto triangulation = CGAL::make_mesh_3<cgal::Triangulation>( meshDomain,
meshCriteria );
return 0;
}

Answer 1

From here:
This surface must be free of intersection.
In your case, the bounding box and midplane intersect. If you want to mesh this geometry, those meshes need to be connected together ahead of meshing.
If you look at the example in section 3.3.2 here, you see a similar example with an internal geometry that is enclosed away from the bounding box.
detect_features() doesn't intersect non-intersecting inputs: it just looks for features in an existing mesh (and adds them to the domain so meshing will respect them).

Answer 2

For your cube it should be easy to construct a polyhedral complex, that is three surfaces, namely the upper and lower part of the cube, and the mid-square. Have a look at this example.