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Segmentize circular strings the same way in both directions, avoiding…

… problems with tiny gaps/overlaps
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mhugent committed Feb 20, 2017
1 parent 7732d73 commit 3da44134d844021924b648403c3888e184eb88fb
Showing with 35 additions and 40 deletions.
  1. +35 −40 src/core/geometry/qgscircularstring.cpp
@@ -487,27 +487,32 @@ void QgsCircularString::setPoints( const QgsPointSequence &points )

void QgsCircularString::segmentize( const QgsPointV2& p1, const QgsPointV2& p2, const QgsPointV2& p3, QgsPointSequence &points, double tolerance, SegmentationToleranceType toleranceType ) const
{
bool clockwise = false;
int segSide = segmentSide( p1, p3, p2 );
if ( segSide == -1 )
{
clockwise = true;
}

QgsPointV2 circlePoint1 = clockwise ? p3 : p1;
QgsPointV2 circlePoint2 = p2;
QgsPointV2 circlePoint3 = clockwise ? p1 : p3 ;

//adapted code from postgis
double radius = 0;
double centerX = 0;
double centerY = 0;
QgsGeometryUtils::circleCenterRadius( p1, p2, p3, radius, centerX, centerY );
int segSide = segmentSide( p1, p3, p2 );
QgsGeometryUtils::circleCenterRadius( circlePoint1, circlePoint2, circlePoint3, radius, centerX, centerY );

if ( p1 != p3 && ( radius < 0 || qgsDoubleNear( segSide, 0.0 ) ) ) //points are colinear

if ( circlePoint1 != circlePoint3 && ( radius < 0 || qgsDoubleNear( segSide, 0.0 ) ) ) //points are colinear
{
points.append( p1 );
points.append( p2 );
points.append( p3 );
return;
}

bool clockwise = false;
if ( segSide == -1 )
{
clockwise = true;
}

double increment = tolerance; //one segment per degree
if ( toleranceType == QgsAbstractGeometry::MaximumDifference )
{
@@ -516,27 +521,15 @@ void QgsCircularString::segmentize( const QgsPointV2& p1, const QgsPointV2& p2,
}

//angles of pt1, pt2, pt3
double a1 = atan2( p1.y() - centerY, p1.x() - centerX );
double a2 = atan2( p2.y() - centerY, p2.x() - centerX );
double a3 = atan2( p3.y() - centerY, p3.x() - centerX );
double a1 = atan2( circlePoint1.y() - centerY, circlePoint1.x() - centerX );
double a2 = atan2( circlePoint2.y() - centerY, circlePoint2.x() - centerX );
double a3 = atan2( circlePoint3.y() - centerY, circlePoint3.x() - centerX );

if ( clockwise )
{
increment *= -1;
/* Adjust a3 down so we can decrement from a1 to a3 cleanly */
if ( a3 >= a1 )
a3 -= 2.0 * M_PI;
if ( a2 > a1 )
a2 -= 2.0 * M_PI;
}
else
{
/* Adjust a3 up so we can increment from a1 to a3 cleanly */
if ( a3 <= a1 )
a3 += 2.0 * M_PI;
if ( a2 < a1 )
a2 += 2.0 * M_PI;
}
/* Adjust a3 up so we can increment from a1 to a3 cleanly */
if ( a3 <= a1 )
a3 += 2.0 * M_PI;
if ( a2 < a1 )
a2 += 2.0 * M_PI;

bool hasZ = is3D();
bool hasM = isMeasure();
@@ -545,8 +538,9 @@ void QgsCircularString::segmentize( const QgsPointV2& p1, const QgsPointV2& p2,
double z = 0;
double m = 0;

points.append( p1 );
if ( p2 != p3 && p1 != p2 ) //draw straight line segment if two points have the same position
QList<QgsPointV2> stringPoints;
stringPoints.insert( clockwise ? 0 : stringPoints.size(), circlePoint1 );
if ( circlePoint2 != circlePoint3 && circlePoint1 != circlePoint2 ) //draw straight line segment if two points have the same position
{
QgsWkbTypes::Type pointWkbType = QgsWkbTypes::Point;
if ( hasZ )
@@ -556,16 +550,16 @@ void QgsCircularString::segmentize( const QgsPointV2& p1, const QgsPointV2& p2,

//make sure the curve point p2 is part of the segmentized vertices. But only if p1 != p3
bool addP2 = true;
if ( qgsDoubleNear( p1.x(), p3.x() ) && qgsDoubleNear( p1.y(), p3.y() ) )
if ( qgsDoubleNear( circlePoint1.x(), circlePoint3.x() ) && qgsDoubleNear( circlePoint1.y(), circlePoint3.y() ) )
{
addP2 = false;
}

for ( double angle = a1 + increment; clockwise ? angle > a3 : angle < a3; angle += increment )
for ( double angle = a1 + increment; angle < a3; angle += increment )
{
if (( addP2 && clockwise && angle < a2 ) || ( addP2 && !clockwise && angle > a2 ) )
if (( addP2 && angle > a2 ) )
{
points.append( p2 );
stringPoints.insert( clockwise ? 0 : stringPoints.size(), circlePoint2 );
addP2 = false;
}

@@ -574,23 +568,24 @@ void QgsCircularString::segmentize( const QgsPointV2& p1, const QgsPointV2& p2,

if ( !hasZ && !hasM )
{
points.append( QgsPointV2( x, y ) );
stringPoints.insert( clockwise ? 0 : stringPoints.size(), QgsPointV2( x, y ) );
continue;
}

if ( hasZ )
{
z = interpolateArc( angle, a1, a2, a3, p1.z(), p2.z(), p3.z() );
z = interpolateArc( angle, a1, a2, a3, circlePoint1.z(), circlePoint2.z(), circlePoint3.z() );
}
if ( hasM )
{
m = interpolateArc( angle, a1, a2, a3, p1.m(), p2.m(), p3.m() );
m = interpolateArc( angle, a1, a2, a3, circlePoint1.m(), circlePoint2.m(), circlePoint3.m() );
}

points.append( QgsPointV2( pointWkbType, x, y, z, m ) );
stringPoints.insert( clockwise ? 0 : stringPoints.size(), QgsPointV2( pointWkbType, x, y, z, m ) );
}
}
points.append( p3 );
stringPoints.insert( clockwise ? 0 : stringPoints.size(), circlePoint3 );
points.append( stringPoints );
}

int QgsCircularString::segmentSide( const QgsPointV2& pt1, const QgsPointV2& pt3, const QgsPointV2& pt2 ) const

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