CGAL users discussion list

[ochyomdu <>]

Dear Bose,

Your small extracted code looks similar to my problem case. I also use
Polyhedron_3 and Nef_polyhedron_3.

And I have similar problems with using of traits/kernel.

I will be grateful when You can give me Your new small extracted code of
Your solution for this problem.

Much success to You in this new Year!



Bose wrote
> 
> Dear Marc,
> 
> Thanks, It works even with CGAL::Gmpq, after converting types in normal
> calculation.
> 
> With regards,
> 
> Bose
> 
> -----Original Message-----
> From: Marc Glisse 
> [mailto:marc.glisse@]
>  
> Sent: Monday, October 04, 2010 2:46 PM
> To: 
> cgal-discuss@.inria
> Subject: RE: [cgal-discuss] Operator Overloading problem for Vector in
> Gmpzf
> Kernel
> 
> Wow, you seem to be out of luck.
> 
> Nef_* looks very limited in the kernels it accepts (basically only those 
> where the number type is a quotient), and because the 
> Algebraic_structure_traits doesn't provide a default trivial gcd for field 
> types, you can't even provide a Fraction_trait for CORE::Expr and pretend 
> it is a quotient (or use a CGAL::Quotient<CORE::Expr>).
> 
> typedef CGAL::Simple_cartesian&lt;CGAL::Quotient&lt;CGAL::Gmpz&gt; >
> Kernel;
> may compile, though the square root will be far from accurate.
> 
> An Sqrt_extension of Gmpq looks promizing, but it also seems to be missing 
> required pieces.
> 
> You may be able to convert back and forth between types, say:
> n = n / Kernel::FT(CGAL::sqrt(CGAL::to_double(n.squared_length())));
> if you don't mind the lack of accuracy.
> 
> On Mon, 4 Oct 2010, S K BOSE wrote:
> 
>> Dear All,
>>
>> Here is my small extracted code. I want to use both Polyhedron_3 and Nef
>> Polyhedra.
>>
>> #include
>> &lt;CGAL/Exact_predicates_exact_constructions_kernel_with_sqrt.h&gt;
>>
>> #include &lt;CGAL/Polyhedron_3.h&gt;
>> #include &lt;CGAL/Nef_polyhedron_3.h&gt;
>>
>> typedef CGAL::Exact_predicates_exact_constructions_kernel_with_sqrt
> Kernel;
>> typedef CGAL::Polyhedron_3<Kernel> Polyhedron;
>> typedef CGAL::Nef_polyhedron_3<Kernel> Nef_polyhedron;
>> typedef Kernel::Point_3   Point_3;
>> typedef Polyhedron::Facet_iterator Facet_iterator;
>> typedef Polyhedron::Halfedge_around_facet_circulator HF_circulator;
>> typedef Kernel::Vector_3          Vector;
>>
>>
>>
>> int main() {
>>
>>  Point_3 p( 1.0, 0.0, 0.0);
>>  Point_3 q( 0.0, 1.0, 0.0);
>>  Point_3 r( 0.0, 0.0, 1.0);
>>  Point_3 s( 0.0, 0.0, 0.0);
>>
>>  Polyhedron P;
>>  P.make_tetrahedron( p, q, r, s);
>>  Nef_polyhedron N(P);
>>  //...........do some boolean operation
>>  if(N.is_simple())
>>  N.convert_to_Polyhedron(P);
>>  Facet_iterator f;
>>  for(f = P.facets_begin(); f != P.facets_end();f++)
>>  {
>>      HF_circulator he = f->facet_begin();
>>      HF_circulator end = he;
>>      CGAL_For_all(he,end)
>>       {
>>          const Point_3& prev = he->prev()->vertex()->point();
>>          const Point_3& curr = he->vertex()->point();
>>          const Point_3& next = he->next()->vertex()->point();
>>          //Vector n = CGAL::cross_product(next-curr,prev-curr);
>>          //  n = n / CGAL::sqrt(n.squared_length());
>>          Vector n = CGAL::unit_normal(prev,curr,next);
>>       }
>>  }
>> }
>>
>>
>> a) If I use "Exact_predicates_exact_constructions_kernel_with_sqrt", it
>> gives error in decomposer(h.b(),num,denom) from Nef_S2/Normalizing.h like
>> 1>G:\cgal\CGAL-3.7-beta1\include\CGAL/Nef_S2/Normalizing.h(306) : error
>> C2064: term does not evaluate to a function taking 3 arguments
>> 1>G:\cgal\CGAL-3.7-beta1\include\CGAL/Nef_S2/Normalizing.h(307) : error
>> C2676: binary '*=' : 'CGAL::Null_tag' does not define this operator or a
>> conversion to a type acceptable to the predefined operator
>> ....................
>> ...................
>>
>> b) If I use "Exact_predicates_exact_constructions_kernel", it gives the
> same
>> old problem as I was getting with homogeneous
>>
>> G:\cgal\CGAL-3.7-beta1\include\CGAL/Kernel/function_objects.h(1878) :
> error
>> C2678: binary '/' : no operator found which takes a left-hand operand of
>> type 'CGAL::Vector_3<R_>' (or there is no acceptable conversion) -----
>>
>> c) If I use "Exact_predicates_inexact_constructions_kernel", it gives
>>
>> G:\cgal\CGAL-3.7-beta1\include\CGAL/Nef_3/Bounding_box_3.h(89) : error
>> C2039: 'lo' : is not a member of
>> 'CGAL::Box_intersection_d::Box_d&lt;NT_,N&gt;'
>>
>> In this context what should be my kernel. My compiler is Microsoft Visual
>> Studio 2005
>>
>> With regards,
>>
>> Bose
>>
>> Original Message-----
>> From: Marc Glisse 
>> [mailto:marc.glisse@]
>> Sent: Tuesday, September 21, 2010 7:01 PM
>> To: 
>> cgal-discuss@.inria
>> Subject: RE: [cgal-discuss] Operator Overloading problem for Vector in
> Gmpzf
>> Kernel
>>
>> On Tue, 21 Sep 2010, S K BOSE wrote:
>>
>>> Thanks for reply. As Marc mentioned it is the problem for homogeneous
>>> Vector, But if I use Exact_predicates_exact_constructions_kernel (which
>>> I
>>> feel it is Cartesian) it gives same problem. Same problem for Gmpq
>>> kernel
>>> also (as what Bernd suggested).
>>
>> If you really need sqrt, you want either an approximate kernel
>> (Exact_predicates_inexact_constructions_kernel may work) or an exact
>> kernel that can handle it
>> (Exact_predicates_exact_constructions_kernel_with_sqrt).
> 
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