用我自己的 Point 类自定义 CGAL 内核

Customizing CGAL Kernel with my own Point class(用我自己的 Point 类自定义 CGAL 内核)

问题描述

我想使用带有 CGAL 约束 delaunay 三角剖分的自定义 Point 类.但是，使用以下 MyPoint 类(其行为应该与 CGAL::Point_2 不完全相同?)我得到分段错误.如果我将 MyKernel 中的 Point_2 typedef 设置为 CGAL::Exact_predicates_inexact_constructions_kernel::Point_2，它会完美运行.我做错了什么?

I would like to use a custom Point class with the CGAL constrained delaunay triangulation. However, with the following MyPoint class (which should behave the exact same as a CGAL::Point_2 no?) I get segmentation faults. It works perfectly if I set the Point_2 typedef inside MyKernel to CGAL::Exact_predicates_inexact_constructions_kernel::Point_2. What am I doing wrong?

template<class P>
struct MyPoint : public P {
    MyPoint() : P() {}
    MyPoint(const MyPoint& p) : P(p) {}

    MyPoint( int x, int y) : P(x,y) {}
    MyPoint( double x, double y) : P(x,y) {}
};

struct MyKernel : CGAL::Exact_predicates_inexact_constructions_kernel {
    typedef MyPoint<CGAL::Exact_predicates_inexact_constructions_kernel::Point_2> Point_2;
};

typedef MyKernel K;

typedef CGAL::Triangulation_vertex_base_2<K>                     Vb;
typedef CGAL::Constrained_triangulation_face_base_2<K>           Fb;
typedef CGAL::Triangulation_data_structure_2<Vb,Fb>              TDS;
typedef CGAL::Exact_predicates_tag                               Itag;
typedef CGAL::Constrained_Delaunay_triangulation_2<K, TDS, Itag> CDT;
typedef CDT::Point          Point;

最后一行出现段错误的代码:

Code which segfaults at last line:

CDT cdt;
Point cgal_p1;
Point cgal_p2;
cgal_p1 = Point(p1[1],p1[2]);
cgal_p2 = Point(p2[1],p2[2]);
cdt.insert_constraint(cgal_p1,
                      cgal_p2);

推荐答案

更改内核很棘手.这里发生的情况是，从三角剖分类来看，与内核相比唯一改变的是点类型，通过派生而来.这对于谓词函子来说已经足够了，但对于构​​造函子(例如 CDT 所需的交集)来说就不够了.

Changing the kernel is tricky. What happens here is that, seen from the triangulation class, the only thing that changes compared to the kernel is the point type, by deriving from it. This can be good enough for predicates functors, but not for constructions functors, like the intersection that is required by the CDT.

我认为你有两个选择:

1. 为 ConstrainedTriangulationTraits_2 适合您的类型.

使用 可扩展内核 应该做你想做的事情的机制.

Use the Extensible Kernel mechanism that is supposed to do what you want.

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