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Numerically more robust circle center calculation. Provided by Timo I…

…ipponen
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mhugent committed Dec 22, 2015
1 parent 9d81938 commit 644960e50a1f06849bc6b1a7e878a68b7f36e802
Showing with 26 additions and 19 deletions.
  1. +26 −19 src/core/geometry/qgsgeometryutils.cpp
@@ -280,7 +280,7 @@ double QgsGeometryUtils::ccwAngle( double dy, double dx )

void QgsGeometryUtils::circleCenterRadius( const QgsPointV2& pt1, const QgsPointV2& pt2, const QgsPointV2& pt3, double& radius, double& centerX, double& centerY )
{
double temp, bc, cd, det;
double dx21, dy21, dx31, dy31, h21, h31, d;

//closed circle
if ( qgsDoubleNear( pt1.x(), pt3.x() ) && qgsDoubleNear( pt1.y(), pt3.y() ) )
@@ -291,22 +291,29 @@ void QgsGeometryUtils::circleCenterRadius( const QgsPointV2& pt1, const QgsPoint
return;
}

temp = pt2.x() * pt2.x() + pt2.y() * pt2.y();
bc = ( pt1.x() * pt1.x() + pt1.y() * pt1.y() - temp ) / 2.0;
cd = ( temp - pt3.x() * pt3.x() - pt3.y() * pt3.y() ) / 2.0;
det = ( pt1.x() - pt2.x() ) * ( pt2.y() - pt3.y() ) - ( pt2.x() - pt3.x() ) * ( pt1.y() - pt2.y() );
// Using cartesian circumcenter eguations from page https://en.wikipedia.org/wiki/Circumscribed_circle
dx21 = pt2.x() - pt1.x();
dy21 = pt2.y() - pt1.y();
dx31 = pt3.x() - pt1.x();
dy31 = pt3.y() - pt1.y();

/* Check colinearity */
if ( qgsDoubleNear( fabs( det ), 0.0, 0.00000000001 ) )
h21 = pow( dx21, 2.0 ) + pow( dy21, 2.0 );
h31 = pow( dx31, 2.0 ) + pow( dy31, 2.0 );

// 2*Cross product, d<0 means clockwise and d>0 counterclockwise sweeping angle
d = 2 * ( dx21 * dy31 - dx31 * dy21 );

// Check colinearity, Cross product = 0
if ( qgsDoubleNear( fabs( d ), 0.0, 0.00000000001 ) )
{
radius = -1.0;
return;
}

det = 1.0 / det;
centerX = ( bc * ( pt2.y() - pt3.y() ) - cd * ( pt1.y() - pt2.y() ) ) * det;
centerY = (( pt1.x() - pt2.x() ) * cd - ( pt2.x() - pt3.x() ) * bc ) * det;
radius = sqrt(( centerX - pt1.x() ) * ( centerX - pt1.x() ) + ( centerY - pt1.y() ) * ( centerY - pt1.y() ) );
// Calculate centroid coordinates and radius
centerX = pt1.x() + ( h21 * dy31 - h31 * dy21 ) / d;
centerY = pt1.y() - ( h21 * dx31 - h31 * dx21 ) / d;
radius = sqrt( pow( centerX - pt1.x(), 2.0 ) + pow( centerY - pt1.y(), 2.0 ) );
}

bool QgsGeometryUtils::circleClockwise( double angle1, double angle2, double angle3 )
@@ -481,7 +488,7 @@ QList<QgsPointV2> QgsGeometryUtils::pointsFromWKT( const QString &wktCoordinateL
//first scan through for extra unexpected dimensions
bool foundZ = false;
bool foundM = false;
Q_FOREACH ( const QString& pointCoordinates, coordList )
Q_FOREACH( const QString& pointCoordinates, coordList )
{
QStringList coordinates = pointCoordinates.split( ' ', QString::SkipEmptyParts );
if ( coordinates.size() == 3 && !foundZ && !foundM && !is3D && !isMeasure )
@@ -499,7 +506,7 @@ QList<QgsPointV2> QgsGeometryUtils::pointsFromWKT( const QString &wktCoordinateL
}
}

Q_FOREACH ( const QString& pointCoordinates, coordList )
Q_FOREACH( const QString& pointCoordinates, coordList )
{
QStringList coordinates = pointCoordinates.split( ' ', QString::SkipEmptyParts );
if ( coordinates.size() < dim )
@@ -542,7 +549,7 @@ QList<QgsPointV2> QgsGeometryUtils::pointsFromWKT( const QString &wktCoordinateL
void QgsGeometryUtils::pointsToWKB( QgsWkbPtr& wkb, const QList<QgsPointV2> &points, bool is3D, bool isMeasure )
{
wkb << static_cast<quint32>( points.size() );
Q_FOREACH ( const QgsPointV2& point, points )
Q_FOREACH( const QgsPointV2& point, points )
{
wkb << point.x() << point.y();
if ( is3D )
@@ -559,7 +566,7 @@ void QgsGeometryUtils::pointsToWKB( QgsWkbPtr& wkb, const QList<QgsPointV2> &poi
QString QgsGeometryUtils::pointsToWKT( const QList<QgsPointV2>& points, int precision, bool is3D, bool isMeasure )
{
QString wkt = "(";
Q_FOREACH ( const QgsPointV2& p, points )
Q_FOREACH( const QgsPointV2& p, points )
{
wkt += qgsDoubleToString( p.x(), precision );
wkt += ' ' + qgsDoubleToString( p.y(), precision );
@@ -581,8 +588,8 @@ QDomElement QgsGeometryUtils::pointsToGML2( const QList<QgsPointV2>& points, QDo

QString strCoordinates;

Q_FOREACH ( const QgsPointV2& p, points )
strCoordinates += qgsDoubleToString( p.x(), precision ) + ',' + qgsDoubleToString( p.y(), precision ) + ' ';
Q_FOREACH( const QgsPointV2& p, points )
strCoordinates += qgsDoubleToString( p.x(), precision ) + ',' + qgsDoubleToString( p.y(), precision ) + ' ';

if ( strCoordinates.endsWith( ' ' ) )
strCoordinates.chop( 1 ); // Remove trailing space
@@ -597,7 +604,7 @@ QDomElement QgsGeometryUtils::pointsToGML3( const QList<QgsPointV2>& points, QDo
elemPosList.setAttribute( "srsDimension", is3D ? 3 : 2 );

QString strCoordinates;
Q_FOREACH ( const QgsPointV2& p, points )
Q_FOREACH( const QgsPointV2& p, points )
{
strCoordinates += qgsDoubleToString( p.x(), precision ) + ' ' + qgsDoubleToString( p.y(), precision ) + ' ';
if ( is3D )
@@ -613,7 +620,7 @@ QDomElement QgsGeometryUtils::pointsToGML3( const QList<QgsPointV2>& points, QDo
QString QgsGeometryUtils::pointsToJSON( const QList<QgsPointV2>& points, int precision )
{
QString json = "[ ";
Q_FOREACH ( const QgsPointV2& p, points )
Q_FOREACH( const QgsPointV2& p, points )
{
json += '[' + qgsDoubleToString( p.x(), precision ) + ", " + qgsDoubleToString( p.y(), precision ) + "], ";
}

4 comments on commit 644960e

@m-kuhn

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@m-kuhn m-kuhn replied Dec 22, 2015

Thank you @mhugent and Timo

Can you run

./scripts/astyle.sh src/core/geometry/qgsgeometryutils.cpp

to fix the indentation and tests.

FYI, there is a simple automated solution to avoid formatting issues

https://github.com/m-kuhn/QGIS-Website/blob/qtcreator.rst/source/site/getinvolved/development/git.rst#setup-pre-commit-hook

@mhugent

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@mhugent mhugent replied Dec 22, 2015

@m-kuhn : I did run prepare-commit. running astyle again consequently says:

./scripts/astyle.sh src/core/geometry/qgsgeometryutils.cpp
flip not found
autopep8 not found
unchanged* src/core/geometry/qgsgeometryutils.cpp

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@m-kuhn m-kuhn replied Dec 22, 2015

hmm... did you enable WITH_ASTYLE in cmake?

@mhugent

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@mhugent mhugent replied Dec 22, 2015

@m-kuhn: it was indeed off

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