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fix the test ``collapse_does_not_invert_face()` 

Testing orientation of normals per patch (identified by their Id) is not a
good solution, because it can happen that we are trying to collapse an edge
that is sharp but which has both of its incident faces on the same surface
patch (wrt ids).

The new test is a lot simpler : for each non-degenerate face of the link of
the edge to be collapsed, simply check if its own normal has changed
orientation or not. The adjacent faces do not need to be taken into account
This commit is contained in:
Jane Tournois 2019-03-05 16:50:30 +01:00
parent 56d1559dc7
commit 6f12a4ab6f
1 changed files with 35 additions and 7 deletions
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42
Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/remesh_impl.h
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@ -39,6 +39,7 @@
#include <CGAL/iterator.h>
#include <CGAL/boost/graph/Euler_operations.h>
#include <CGAL/boost/graph/properties.h>
#include <CGAL/boost/graph/helpers.h>
#include <boost/graph/graph_traits.hpp>
#include <boost/foreach.hpp>
#include <CGAL/tags.h>
@ -1421,19 +1422,46 @@ private:
{
vertex_descriptor vs = source(h, mesh_);
vertex_descriptor vt = target(h, mesh_);
//collect normals to faces around vs AND vt
boost::unordered_map<halfedge_descriptor, Vector_3> normals_before_collapse;
BOOST_FOREACH(halfedge_descriptor hd,
boost::range::join(halfedges_around_target(h, mesh_),
halfedges_around_target(opposite(h, mesh_), mesh_)))
{
normals_before_collapse[hd] = compute_normal(face(hd, mesh_));
//note `compute_normal()` returns CGAL::NULL_VECTOR for degenerate faces
}
//backup source point
Point ps = get(vpmap_, vs);
//move source at target
put(vpmap_, vs, get(vpmap_, vt));
//collect normals to faces around vs AND vt
//vertices are at the same location, but connectivity is still be same,
//now vertices are at the same location, but connectivity is still the same,
//with plenty of degenerate triangles (which are common to both stars)
bool res = check_normals(
boost::range::join(
halfedges_around_target(h, mesh_),
halfedges_around_target(opposite(h, mesh_), mesh_)));
//check that normals to non-degenerate faces have not been inverted
//(i.e. they are still pointing in the same direction)
bool res = true;
BOOST_FOREACH(halfedge_descriptor hd,
boost::range::join(
halfedges_around_target(h, mesh_),
halfedges_around_target(opposite(h, mesh_), mesh_)))
{
face_descriptor fd = face(hd, mesh_);
if ( fd == boost::graph_traits<PM>::null_face()
|| is_degenerate_triangle_face(fd, mesh_, vpmap_, GeomTraits()))
continue;
Vector_3 n_after = compute_normal(face(hd, mesh_)); //deals with degenerate faces
Vector_3 n_before = normals_before_collapse[hd];
if (n_after * n_before <= 0)
{
res = false;
break;
}
}
//restore position
put(vpmap_, vs, ps);