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Better way to seek value of t.

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--HG--
branch : develop
This commit is contained in:
Roman Telezhynskyi 2016-03-15 17:31:58 +02:00
parent a91112faee
commit a56c3354e1
1 changed files with 15 additions and 19 deletions
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32
src/libs/vgeometry/vabstractcubicbezier.cpp
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@ -83,45 +83,41 @@ QPointF VAbstractCubicBezier::CutSpline(qreal length, QPointF &spl1p2, QPointF &
length = GetLength()*0.98; length = GetLength()*0.98;
} }
// Very stupid way find correct value of t. const qreal eps = 0.001 * qAbs(length);
// Better first compare with t = 0.5. Find length of spline. qreal parT = 0.5;
// If length larger, take t = 0.75 and so on. qreal step = parT;
// If length less, take t = 0.25 and so on.
qreal parT = 0;
qreal step = 0.001;
while (1)
{
parT = parT + step;
qreal splLength = LengthT(parT); qreal splLength = LengthT(parT);
if (splLength >= length || parT > 1)
while (qAbs(splLength - length) > eps)
{ {
break; step = step/2.0;
} splLength > length ? parT -= step : parT += step;
splLength = LengthT(parT);
} }
QLineF seg1_2 ( GetP1 ().toQPointF(), GetControlPoint1 () ); QLineF seg1_2 ( GetP1 ().toQPointF(), GetControlPoint1 () );
seg1_2.setLength(seg1_2.length () * parT); seg1_2.setLength(seg1_2.length () * parT);
QPointF p12 = seg1_2.p2(); const QPointF p12 = seg1_2.p2();
QLineF seg2_3 ( GetControlPoint1(), GetControlPoint2 () ); QLineF seg2_3 ( GetControlPoint1(), GetControlPoint2 () );
seg2_3.setLength(seg2_3.length () * parT); seg2_3.setLength(seg2_3.length () * parT);
QPointF p23 = seg2_3.p2(); const QPointF p23 = seg2_3.p2();
QLineF seg12_23 ( p12, p23 ); QLineF seg12_23 ( p12, p23 );
seg12_23.setLength(seg12_23.length () * parT); seg12_23.setLength(seg12_23.length () * parT);
QPointF p123 = seg12_23.p2(); const QPointF p123 = seg12_23.p2();
QLineF seg3_4 ( GetControlPoint2 (), GetP4 ().toQPointF() ); QLineF seg3_4 ( GetControlPoint2 (), GetP4 ().toQPointF() );
seg3_4.setLength(seg3_4.length () * parT); seg3_4.setLength(seg3_4.length () * parT);
QPointF p34 = seg3_4.p2(); const QPointF p34 = seg3_4.p2();
QLineF seg23_34 ( p23, p34 ); QLineF seg23_34 ( p23, p34 );
seg23_34.setLength(seg23_34.length () * parT); seg23_34.setLength(seg23_34.length () * parT);
QPointF p234 = seg23_34.p2(); const QPointF p234 = seg23_34.p2();
QLineF seg123_234 ( p123, p234 ); QLineF seg123_234 ( p123, p234 );
seg123_234.setLength(seg123_234.length () * parT); seg123_234.setLength(seg123_234.length () * parT);
QPointF p1234 = seg123_234.p2(); const QPointF p1234 = seg123_234.p2();
spl1p2 = p12; spl1p2 = p12;
spl1p3 = p123; spl1p3 = p123;