CGAL users discussion list

[Hoang Giang Bui <>]

Thanks for the clarification 

Giang

> On 15 Apr 2016, at 10:19, Sebastien Loriot (GeometryFactory) 
> <>
>  wrote:
> 
> IIRC, in order to compute the offset, a large bbox is put around the input 
> model. The extra output polygon is the offset of the bbox.
> 
> Sebastien.
> 
>> On 04/15/2016 09:46 AM, Hoang Giang Bui wrote:
>> Hello
>> 
>> I have a simple question. To create an offset polygon I used the code
>> from examples:
>> 
>>  Polygon_2 poly ;
>>   poly.push_back( Point(0,0) ) ;
>>   poly.push_back( Point(1,0) ) ;
>>   poly.push_back( Point(1,1) ) ;
>>   poly.push_back( Point(0,1) ) ;
>> 
>>   FT lOffset = 0.1 ;
>>   PolygonPtrVector outer_offset_polygons =
>> CGAL::create_exterior_skeleton_and_offset_polygons_2(lOffset,poly);
>>   print_polygons(outer_offset_polygons);
>> 
>> But it produces two polygons:
>> 
>> Polygon list with 2 polygons
>> Polygon with 4 vertices
>> (-0.146421,-0.146421)
>> (1.14642,-0.146421)
>> (1.14642,1.14642)
>> (-0.146421,1.14642)
>> Polygon with 4 vertices
>> (-0.1,1.1)
>> (1.1,1.1)
>> (1.1,-0.1)
>> (-0.1,-0.1)
>> 
>> The second is correct but the first seems hard to understand. Does
>> anyone have idea what it is?
>> 
>> Giang
> 
> 
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