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Fix Compare_xy_2 for the generic 3D projection traits (#8810) 

## Summary of Changes

The previous implementation defined `Compare_xy_2` as simply
`Compare_xyz_3`. This does define an order over the projected points,
but it has a strong downside: it ignores the direction of the normal, so
its order can be the opposite of the lexicographical order
would give. This new order is in conflict with the existing
`Compare_x_2` and `Compare_y_2`, which take the normal's direction into
account.

(Also with the `Less_x_2`, `Less_y_2`, and `Less_xy_2` family, which
also exist for the projection traits.)

## Release Management

* Affected package(s): `Kernel_23`
* Issue(s) solved (if any): -
* Feature/Small Feature (if any): - 
* License and copyright ownership: no change
This commit is contained in:
Sebastien Loriot 2025-04-03 15:54:37 +02:00 committed by GitHub
parent a838073ec7 b4422374a0
commit b45c29edd4
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GPG Key ID: B5690EEEBB952194
1 changed files with 37 additions and 4 deletions
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41
Kernel_23/include/CGAL/Kernel_23/internal/Projection_traits_base_3.h
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@ -372,6 +372,35 @@ public:
}
}; // end class Less_xy_along_axis
template <class Traits>
class Compare_xy_along_axis
{
// private members
typedef typename Traits::Vector_3 Vector_3;
typedef typename Traits::Point_2 Point;
Vector_3 base1, base2;
public:
Compare_xy_along_axis(const Vector_3& base1, const Vector_3& base2) : base1(base1), base2(base2)
{
CGAL_PROFILER("Construct Compare_xy_along_axis")
CGAL_TIME_PROFILER("Construct Compare_xy_along_axis")
}
typedef Comparison_result result_type;
Comparison_result operator()(const Point& p, const Point& q) const
{
Compare_along_axis<Traits> cx(base1);
Comparison_result crx = cx(p, q);
if (crx != EQUAL) {
return crx;
}
Compare_along_axis<Traits> cy(base2);
return cy(p, q);
}
}; // end class Compare_xy_along_axis
} // end namespace TriangulationProjectionTraitsCartesianFunctors
@ -426,12 +455,13 @@ public:
typedef typename K::Line_3 Line_2;
typedef typename K::Angle_3 Angle_2;
typedef typename K::Compare_xyz_3 Compare_xy_2;
typedef TriangulationProjectionTraitsCartesianFunctors::
Compare_along_axis<Self> Compare_x_2;
typedef TriangulationProjectionTraitsCartesianFunctors::
Compare_along_axis<Self> Compare_y_2;
typedef TriangulationProjectionTraitsCartesianFunctors::
Compare_xy_along_axis<Self> Compare_xy_2;
typedef TriangulationProjectionTraitsCartesianFunctors::
Less_along_axis<Self> Less_x_2;
@ -498,6 +528,12 @@ public:
return Compare_y_2(this->base2());
}
Compare_xy_2
compare_xy_2_object() const
{
return Compare_xy_2(this->base1(), this->base2());
}
Orientation_2
orientation_2_object() const
{
@ -525,9 +561,6 @@ public:
Angle_2 angle_2_object() const
{return Angle_2();}
Compare_xy_2 compare_xy_2_object() const
{return Compare_xy_2();}
Construct_point_2 construct_point_2_object() const
{return Construct_point_2();}