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Fix CDT_2 errors, using snapping of intersection points 

When `Constrained_triangulation_2` computes the intersection of two
segments, with a floating-point number type, and with
`Exact_predicates_tag`, the computed intersection point is snapped to an
extremity of the two segments, if it is closest to 4 ulp (with the l-inf
distance).

That value `4` can be changed by defining the macro
`CGAL_CDT_2_INTERSECTION_SNAPPING_ULP_DISTANCE` to another value.
This commit is contained in:
Laurent Rineau 2018-05-18 17:47:01 +02:00
parent 5d0858a379
commit c40d7124d0
1 changed files with 63 additions and 1 deletions
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64
Triangulation_2/include/CGAL/Constrained_triangulation_2.h
View File

@ -37,6 +37,9 @@
#include <boost/mpl/if.hpp>
#include <boost/iterator/filter_iterator.hpp>
#include <boost/math/special_functions/next.hpp>
#include <boost/type_traits/is_floating_point.hpp>
namespace CGAL {
struct No_intersection_tag{};
@ -1422,11 +1425,70 @@ intersection(const Gt& gt,
const typename Gt::Point_2& pc,
const typename Gt::Point_2& pd,
typename Gt::Point_2& pi,
Exact_predicates_tag)
Exact_predicates_tag,
CGAL::Tag_false /* not a FT is not floating-point */)
{
return compute_intersection(gt,pa,pb,pc,pd,pi);
}
template<class Gt>
inline bool
intersection(const Gt& gt,
const typename Gt::Point_2& pa,
const typename Gt::Point_2& pb,
const typename Gt::Point_2& pc,
const typename Gt::Point_2& pd,
typename Gt::Point_2& pi,
Exact_predicates_tag,
CGAL::Tag_true /* FT is a floating-point type */)
{
const bool result = compute_intersection(gt,pa,pb,pc,pd,pi);
if(!result) return result;
if(pi == pa || pi == pb || pi == pc || pi == pd) {
#ifdef CGAL_CDT_2_DEBUG_INTERSECTIONS
std::cerr << " CT_2::intersection: intersection is an existing point "
<< pi << std::endl;
#endif
return result;
}
using boost::math::float_advance;
#ifdef CGAL_CDT_2_INTERSECTION_SNAPPING_ULP_DISTANCE
const int dist = CGAL_CDT_2_INTERSECTION_SNAPPING_ULP_DISTANCE;
#else
const int dist = 4;
#endif
const Bbox_2 bbox(float_advance(pi.x(), -dist), float_advance(pi.y(), -dist),
float_advance(pi.x(), +dist), float_advance(pi.y(), +dist));
if(do_overlap(bbox, pa.bbox())) pi = pa;
if(do_overlap(bbox, pb.bbox())) pi = pb;
if(do_overlap(bbox, pc.bbox())) pi = pc;
if(do_overlap(bbox, pd.bbox())) pi = pd;
#ifdef CGAL_CDT_2_DEBUG_INTERSECTIONS
if(pi == pa || pi == pb || pi == pc || pi == pd) {
std::cerr << " CT_2::intersection: intersection SNAPPED to an existing point "
<< pi << std::endl;
}
#endif
return result;
}
template<class Gt>
inline bool
intersection(const Gt& gt,
const typename Gt::Point_2& pa,
const typename Gt::Point_2& pb,
const typename Gt::Point_2& pc,
const typename Gt::Point_2& pd,
typename Gt::Point_2& pi,
Exact_predicates_tag exact_predicates_tag)
{
typedef typename Gt::FT FT;
return intersection(gt,pa,pb,pc,pd,pi,
exact_predicates_tag,
Boolean_tag<boost::is_floating_point<FT>::value>());
}
template<class Gt>
bool