bool QgsTransectSample::closestSegmentPoints( const QgsGeometry& g1, const QgsGeometry& g2, double& dist, QgsPoint& pt1, QgsPoint& pt2 )
{
QgsWkbTypes::Type t1 = g1.wkbType();
if ( t1 != QgsWkbTypes::LineString && t1 != QgsWkbTypes::LineString25D )
{
return false;
}
QgsWkbTypes::Type t2 = g2.wkbType();
if ( t2 != QgsWkbTypes::LineString && t2 != QgsWkbTypes::LineString25D )
{
return false;
}
QgsPolyline pl1 = g1.asPolyline();
QgsPolyline pl2 = g2.asPolyline();
if ( pl1.size() < 2 || pl2.size() < 2 )
{
return false;
}
QgsPoint p11 = pl1.at( 0 );
QgsPoint p12 = pl1.at( 1 );
QgsPoint p21 = pl2.at( 0 );
QgsPoint p22 = pl2.at( 1 );
double p1x = p11.x();
double p1y = p11.y();
double v1x = p12.x() - p11.x();
double v1y = p12.y() - p11.y();
double p2x = p21.x();
double p2y = p21.y();
double v2x = p22.x() - p21.x();
double v2y = p22.y() - p21.y();
double denominatorU = v2x * v1y - v2y * v1x;
double denominatorT = v1x * v2y - v1y * v2x;
if ( qgsDoubleNear( denominatorU, 0 ) || qgsDoubleNear( denominatorT, 0 ) )
{
//lines are parallel
//project all points on the other segment and take the one with the smallest distance
QgsPoint minDistPoint1;
double d1 = p11.sqrDistToSegment( p21.x(), p21.y(), p22.x(), p22.y(), minDistPoint1 );
QgsPoint minDistPoint2;
double d2 = p12.sqrDistToSegment( p21.x(), p21.y(), p22.x(), p22.y(), minDistPoint2 );
QgsPoint minDistPoint3;
double d3 = p21.sqrDistToSegment( p11.x(), p11.y(), p12.x(), p12.y(), minDistPoint3 );
QgsPoint minDistPoint4;
double d4 = p22.sqrDistToSegment( p11.x(), p11.y(), p12.x(), p12.y(), minDistPoint4 );
if ( d1 <= d2 && d1 <= d3 && d1 <= d4 )
{
dist = sqrt( d1 );
pt1 = p11;
pt2 = minDistPoint1;
return true;
}
else if ( d2 <= d1 && d2 <= d3 && d2 <= d4 )
{
dist = sqrt( d2 );
pt1 = p12;
pt2 = minDistPoint2;
return true;
}
else if ( d3 <= d1 && d3 <= d2 && d3 <= d4 )
{
dist = sqrt( d3 );
pt1 = p21;
pt2 = minDistPoint3;
return true;
}
else
{
dist = sqrt( d4 );
pt1 = p21;
pt2 = minDistPoint4;
return true;
}
}
double u = ( p1x * v1y - p1y * v1x - p2x * v1y + p2y * v1x ) / denominatorU;
double t = ( p2x * v2y - p2y * v2x - p1x * v2y + p1y * v2x ) / denominatorT;
if ( u >= 0 && u <= 1.0 && t >= 0 && t <= 1.0 )
{
dist = 0;
pt1.setX( p2x + u * v2x );
pt1.setY( p2y + u * v2y );
pt2 = pt1;
dist = 0;
return true;
}
if ( t > 1.0 )
{
pt1.setX( p12.x() );
pt1.setY( p12.y() );
}
else if ( t < 0.0 )
{
pt1.setX( p11.x() );
pt1.setY( p11.y() );
}
if ( u > 1.0 )
{
pt2.setX( p22.x() );
pt2.setY( p22.y() );
}
if ( u < 0.0 )
{
pt2.setX( p21.x() );
pt2.setY( p21.y() );
}
if ( t >= 0.0 && t <= 1.0 )
{
//project pt2 onto g1
pt2.sqrDistToSegment( p11.x(), p11.y(), p12.x(), p12.y(), pt1 );
}
if ( u >= 0.0 && u <= 1.0 )
{
//project pt1 onto g2
pt1.sqrDistToSegment( p21.x(), p21.y(), p22.x(), p22.y(), pt2 );
}
dist = sqrt( pt1.sqrDist( pt2 ) );
return true;
}
