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  1. 24th June 2010, 16:13 #1
    lni
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    Default Error in QPolygonF::subtracted

    The following code produces very different result, the only different is the precision (with "f" turn to float), can someone explain please? Many thanks!

    Qt Code: 
    1. #include <QPolygonF>
    2. #include <QDebug>
    3.  
    4. int main()
    5. {
    6.   QPolygonF polygon1;
    7.   polygon1 << QPointF(-49.3670886075949369, 1930.1848049281315980 )
    8.            << QPointF(-34.7848101265822862, 1170.4312114989734255 )
    9.            << QPointF(-13.1139240506329173, 2084.1889117043124315 );
    10.  
    11.   QPolygonF polygon2;
    12.   polygon2 << QPointF(-41.6708860759493689, 1940.4517453798769111 )
    13.            << QPointF(-52.2025316455696142, 431.2114989733059929 )
    14.            << QPointF(-3.3924050632911431, 1509.2402464065710319 )
    15.            << QPointF(-26.8190801175864770, 1506.3079775881415117 )
    16.            << QPointF(-34.7848101265822862, 1170.4312114989734255 )
    17.            << QPointF(-41.1968964968032125, 1504.5083358315471287 );
    18.   qDebug() << "polygon1 - polygon2 = " << polygon1.subtracted( polygon2 );
    19.  
    20.   ////////////////////
    21.   QPolygonF polygon3;
    22.   polygon3 << QPointF(-49.3670886075949369, 1930.1848049281315980 )
    23.            << QPointF(-34.7848101265822862, 1170.4312114989734255 )
    24.            << QPointF(-13.1139240506329173, 2084.1889117043124315 );
    25.  
    26.   QPolygonF polygon4;
    27.   polygon4 << QPointF(-41.6708860759493689f, 1940.4517453798769111f )
    28.            << QPointF(-52.2025316455696142f, 431.2114989733059929f )
    29.            << QPointF(-3.3924050632911431f, 1509.2402464065710319f )
    30.            << QPointF(-26.8190801175864770f, 1506.3079775881415117f )
    31.            << QPointF(-34.7848101265822862f, 1170.4312114989734255f )
    32.            << QPointF(-41.1968964968032125f, 1504.5083358315471287f );
    33.   qDebug() << "polygon3 - polygon4 = " << polygon3.subtracted( polygon4 );
    34.  
    35.   ////////////////////
    36.   QPolygonF polygon5;
    37.   polygon5 << QPointF(-49.3670886075949369f, 1930.1848049281315980 )
    38.            << QPointF(-34.7848101265822862, 1170.4312114989734255 )
    39.            << QPointF(-13.1139240506329173, 2084.1889117043124315 );
    40.  
    41.   QPolygonF polygon6;
    42.   polygon6 << QPointF(-41.6708860759493689, 1940.4517453798769111 )
    43.            << QPointF(-52.2025316455696142, 431.2114989733059929 )
    44.            << QPointF(-3.3924050632911431, 1509.2402464065710319 )
    45.            << QPointF(-26.8190801175864770, 1506.3079775881415117 )
    46.            << QPointF(-34.7848101265822862, 1170.4312114989734255 )
    47.            << QPointF(-41.1968964968032125, 1504.5083358315471287 );
    48.   qDebug() << "polygon5 - polygon6 = " << polygon5.subtracted( polygon6 );
    49.  
    50. }
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    Output is:
    Qt Code: 
    1. polygon1 - polygon2 =  QPolygonF() 
    2. polygon3 - polygon4 =  QPolygonF(QPointF(-49.3671, 1930.18)QPointF(-43.7755, 1638.85)QPointF(-41.6709, 1940.45)QPointF(-41.1969, 1504.51)QPointF(-37.0334, 1287.59)QPointF(-34.7848, 1170.43)QPointF(-27.884, 1461.4)QPointF(-26.8191, 1506.31)QPointF(-26.8191, 1506.31)QPointF(-13.1139, 2084.19)QPointF(-49.3671, 1930.18)) 
    3. polygon5 - polygon6 =  QPolygonF(QPointF(-43.7755, 1638.85)QPointF(-41.1969, 1504.51)QPointF(-41.6709, 1940.45)QPointF(-43.7755, 1638.85))
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  2. 25th June 2010, 01:27 #2
    lni
    lni is offline Advanced user
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    Default Re: Error in QPolygonF::subtracted

    Anyone? Suggestions? Thanks!
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