CGAL users discussion list

[Damian Sheehy <>]

Hi Kim,

According to the code you posted 
>> void ReadPoly(std::istream& is,Polygon_2& pgn, std::string& nextPolyType)

pgn is of type Polygon_2 which has a is_simple() function.
If you cannot view your polygon, then you are working in the dark.
I think you should get some basic plotting capability in place to visually inspect your polygon, and then work from there.


Good luck!


Damian

On Thu, May 14, 2009 at 5:12 PM, Kim <> wrote:

Hi Damian ..

Ones again , thanks for your time .

Unfortunately "is_simple" is not member pgn

Error   1       error C2039: 'is_simple' : is not a member of
'CGAL::General_polygon_2<Arr_traits>'
c:\cgal\projects\likedemo\likedemo\likedemo\likedemo.cpp        117
 likedemo


7 (1.74193e+006 44602.1 1.61312e+006 1) [1.74193e+006 43332 -->
1.7432e+006 44602]
 (1.73489e+006 44595.5 6.90773e+007 1) [1.7432e+006 44602 -->
1.73847e+006 52099]
 (1.73792e+006 50955.1 1.60508e+006 1) [1.73847e+006 52099 -->
1.73792e+006 52222]
 (1.73792e+006 50951.9 1.61312e+006 1) [1.73792e+006 52222 -->
1.73665e+006 50952]
 (1.73792e+006 50952 1.61415e+006 1) [1.73665e+006 50952 --> 1.73737e+006 49805]
 (1.73491e+006 44606.1 3.31029e+007 -1) [1.73737e+006 49805 -->
1.74066e+006 44602]
 (1.74193e+006 44602.1 1.61312e+006 1) [1.74066e+006 44602 -->
1.74193e+006 43332]


as you see, it consist of 7 segments , both start and end are the same
 and the 7 arc as I sent into
as a 3 points arcs they  are not intersecting .


Do anyone have maded a graphic reader for this format which could
check the view.
(Did not get the QT to work ) .

I will try to make a more simple polygon with only one arc and see how
that goes.

Best regards
Kim

On Thu, May 14, 2009 at 6:59 PM, Damian Sheehy <> wrote:
> Hi Kim,
>
> The documentation says;
>
>           Returns the orientation of pgn. If the number of vertices
>           p.size() < 3 then COLLINEAR is returned.
>           Precondition: p.is simple().
>
> The precondition means the code will assert if the polygon is not simple.
> Is your polygon simple? Does it self-intersect?
>
> Check the outcome of pgn.is_simple() to see if your polygon passes the test.
>
> Damian
>
> On Thu, May 14, 2009 at 8:13 AM, Kim <> wrote:
>>
>> Hi Damian , thank for you interest in my problem .
>>
>> if it easier or more helpfull , I can attach my full project , just
>> let me know if needed
>> I had no problem until  I introduced Circle arcs in my X_monotone curves.
>>
>> typeDefs comes longer down for readability
>>
>> void ReadPoly(std::istream& is,Polygon_2& pgn, std::string& nextPolyType)
>> {
>>  XCurve curve;
>>  std::list<XCurve>  xcvs;
>> ..
>> ..
>> //some pseudo code begin
>>
>> do
>>     data<<new data from file
>>      readSegment(data,curve);
>>       xcvs.push_back(curve);
>>
>> loop until no_more_lines.
>> //some pseudo code ends
>>
>> pgn = Polygon_2 (xcvs.begin(), xcvs.end());
>>
>> if (pgn.orientation()==CGAL::CLOCKWISE )  <<--failes -Precondition
>> violation.
>>
>>   pgn.reverse_orientation();
>> }
>>
>> void readSegment(std::string s, XCurve& curve)
>> {
>>  int t;
>>
>>  readSegment_field(s,t);
>>  switch (t)
>>  {
>>  case 0: { // line curvesegment
>>         int sx,sy,ex,ey;
>>         readSegment_line(s,sx,sy,ex,ey);
>>                 Point_2 ps = Point_2(sx,sy);
>>         Point_2 pe = Point_2(ex,ey);
>>
>>         curve = XCurve(ps,pe);
>>
>>                };break;
>>  case 1: { //arc  curvesegment
>>         int sx,sy,mx,my,ex,ey;
>>                 readSegment_arc(s,sx,sy,mx,my,ex,ey);
>>         Point_2 ps = Point_2(sx,sy);  //startpoint
>>         Point_2 pm = Point_2(mx,my); //midpoint
>>         Point_2 pe = Point_2(ex,ey);   //endpoint
>>         Curve c =Curve( ps,pm,pe);
>>          curve =
>> XCurve(c.supporting_circle(),c.source(),c.target(),c.orientation(),0);
>>
>>          //   curve = XCurve(ps,pe); // this did work perfect if used
>> instead of above line
>>                };break;
>>  case 2: {
>>
>>                };break;
>>
>>  } //switch
>> }
>>
>> my typedefs :
>>
>> typedef CGAL::Gmpq                                    Base_nt;
>> typedef CGAL::Lazy_exact_nt<Base_nt>                  Coord_type;
>>
>> struct Kernel : public CGAL::Cartesian<Coord_type> {};
>>
>> typedef Kernel::Point_2                               Point_2;
>> typedef Kernel::Circle_2                              Circle;
>> typedef CGAL::Gps_circle_segment_traits_2<Kernel>     Traits;
>> typedef Traits::Curve_2                               Curve;
>> typedef Traits::X_monotone_curve_2                    XCurve;
>> typedef Traits::Point_2                               Circular_point_2;
>> typedef Traits::Polygon_2                             Polygon_2;
>>
>> best regards
>> kim
>>
>> On Thu, May 14, 2009 at 2:06 PM, Kim Pedersen <> wrote:
>> > Hi Damian , thank for you interest in my problem .
>> >
>> > if it easier or more helpfull , I can attach my full project , just
>> > let me know if needed
>> > I had no problem until  I introduced Circle arcs in my X_monotone
>> > curves.
>> >
>> > typeDefs comes longer down for readability
>> >
>> > void ReadPoly(std::istream& is,Polygon_2& pgn, std::string&
>> > nextPolyType)
>> > {
>> >  XCurve curve;
>> >  std::list<XCurve>  xcvs;
>> > ..
>> > ..
>> > do //some pseudo code
>> >       data<<new data from file
>> >       readSegment(data,curve);
>> >        xcvs.push_back(curve);
>> >
>> > loop until no_more_lines.   //some pseudo code ends
>> >
>> > pgn = Polygon_2 (xcvs.begin(), xcvs.end());
>> >
>> > if (pgn.orientation()==CGAL::CLOCKWISE )  <<--failes here Precondition
>> > violation. , se below
>> >    pgn.reverse_orientation();
>> > }
>> >
>> > void readSegment(std::string s, XCurve& curve)
>> > {
>> >  int t;
>> >
>> >  readSegment_field(s,t);
>> >  switch (t)
>> >  {
>> >   case 0: {
>> >          int sx,sy,ex,ey;
>> >          readSegment_line(s,sx,sy,ex,ey);
>> >                  Point_2 ps = Point_2(sx,sy);
>> >          Point_2 pe = Point_2(ex,ey);
>> >
>> >          curve = XCurve(ps,pe);
>> >
>> >                 };break;
>> >   case 1: {
>> >          int sx,sy,mx,my,ex,ey;
>> >                  readSegment_arc(s,sx,sy,mx,my,ex,ey);
>> >          Point_2 ps = Point_2(sx,sy);  //startpoint
>> >          Point_2 pm = Point_2(mx,my); //midpoint
>> >          Point_2 pe = Point_2(ex,ey);   //endpoint
>> >          Curve c =Curve( ps,pm,pe);
>> >           curve =
>> > XCurve(c.supporting_circle(),c.source(),c.target(),c.orientation(),0);
>> >
>> >           //   curve = XCurve(ps,pe); // this did work perfect if used
>> > instead of above line
>> >                 };break;
>> >   case 2: {
>> >
>> >                 };break;
>> >
>> >   } //switch
>> > }
>> >
>> > my typedefs :
>> >
>> > typedef CGAL::Gmpq                                    Base_nt;
>> > typedef CGAL::Lazy_exact_nt<Base_nt>                  Coord_type;
>> >
>> > struct Kernel : public CGAL::Cartesian<Coord_type> {};
>> >
>> > typedef Kernel::Point_2                               Point_2;
>> > typedef Kernel::Circle_2                              Circle;
>> > typedef CGAL::Gps_circle_segment_traits_2<Kernel>     Traits;
>> > typedef Traits::Curve_2                               Curve;
>> > typedef Traits::X_monotone_curve_2                    XCurve;
>> > typedef Traits::Point_2                               Circular_point_2;
>> > typedef Traits::Polygon_2                             Polygon_2;
>> >
>> > best regards
>> > kim
>> >
>> > On Thu, May 14, 2009 at 3:26 AM, Damian Sheehy <>
>> > wrote:
>> >> Hi Kim,
>> >>
>> >> You need to provide more details.  Which orientation test are you
>> >> using?
>> >> CGAL::orientation(ForwardIterator,ForwardIterator)? It takes two
>> >> arguments.
>> >>
>> >>>> if (pgn.orientation()==CGAL::CLOCKWISE )
>> >> What is png - Portable Network Graphics?
>> >> Damian
>> >> On Wed, May 13, 2009 at 5:49 PM, Kim <> wrote:
>> >>>
>> >>> Hi
>> >>> sorry ! this is a repost ,,,  but I am really stopped.
>> >>>
>> >>> noone has any idear at all ? any clue is appreciated!
>> >>> I am sure the start and endpoint are the same ,, since if I input the
>> >>> same , just as linesegment then it works perfect.
>> >>>
>> >>> Why is the polygon below failing when
>> >>> trying to
>> >>> if (pgn.orientation()==CGAL::CLOCKWISE )   <-- fails with error , see
>> >>> below
>> >>> Precondition violation.
>> >>>
>> >>> I can not see any thing wrong !!
>> >>>
>> >>> Polygon_2(
>> >>>  (Circle_2(PointC2(1.74193e+006, 44602.1),
>> >>> 1.61312e+006,counterclockwise)) [1.74193e+006 43332 --> 1.7432e+006
>> >>> 44602]
>> >>>  (Circle_2(PointC2(1.73489e+006, 44595.5),
>> >>> 6.90773e+007,counterclockwise)) [1.7432e+006 44602 --> 1.73847e+006
>> >>> 52099]
>> >>>  (Circle_2(PointC2(1.73792e+006, 50955.1),
>> >>> 1.60508e+006,counterclockwise)) [1.73847e+006 52099 --> 1.73792e+006
>> >>> 52222]
>> >>>  (Circle_2(PointC2(1.73792e+006, 50951.9),
>> >>> 1.61312e+006,counterclockwise)) [1.73792e+006 52222 --> 1.73665e+006
>> >>> 50952]
>> >>>  (Circle_2(PointC2(1.73792e+006, 50952),
>> >>> 1.61415e+006,counterclockwise)) [1.73665e+006 50952 --> 1.73737e+006
>> >>> 49805]
>> >>>  (Circle_2(PointC2(1.73491e+006, 44606.1), 3.31029e+007,
>> >>> clockwise))[1.73737e+006 49805 --> 1.74066e+006 44602]
>> >>>  (Circle_2(PointC2(1.74193e+006, 44602.1),
>> >>> 1.61312e+006,counterclockwise)) [1.74066e+006 44602 --> 1.74193e+006
>> >>> 43332]
>> >>> )
>> >>> CGAL error: precondition violation!
>> >>> _expression_ : cv1.point_position (p) == EQUAL && cv2.point_position (p)
>> >>> ==
>> >>> EQUAL
>> >>> File       :
>> >>> c:\cgal\cgal-3.4\include\cgal\arr_circle_segment_traits_2.h
>> >>> Line       : 249
>> >>> Explanation:
>> >>> Refer to the bug-reporting instructions at
>> >>> http://www.cgal.org/bug_report.html
>> >>>
>> >>> I did use this way to calc the  the curves:
>> >>>
>> >>> Point_2 ps = Point_2(sx,sy);  //start
>> >>> Point_2 pm = Point_2(mx,my);  //midpoint
>> >>> Point_2 pe = Point_2(ex,ey);  //endpoint
>> >>> Curve c =Curve( ps,pm,pe);
>> >>> curve =
>> >>> XCurve(c.supporting_circle(),c.source(),c.target(),c.orientation(),0);
>> >>>
>> >>> TIA
>> >>> Kim
>> >>> --
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>> >>
>> >>
>> >
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>
>

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