Bug report #16722: Wrong result for curveToLine with max angle 70 on a semicircle - QGIS Application - QGIS Issue Tracking

Bug report #16722

Wrong result for curveToLine with max angle 70 on a semicircle

Added by Sandro Santilli about 7 years ago. Updated almost 7 years ago.

Status:	Closed
Priority:	Normal
Assignee:	Sandro Santilli
Category:	Geometry
Affected QGIS version:	master	Regression?:	No
Operating System:		Easy fix?:	No
Pull Request or Patch supplied:	Yes	Resolution:
Crashes QGIS or corrupts data:	No	Copied to github as #:	24621

Description

This code snippet shows how a MaxAngle:70-degrees linearization of a curve gives a wrong result:

  wkt = QStringLiteral( "CIRCULARSTRING(0 0,100 100,200 0)" );                  
  circularString.reset( dynamic_cast<QgsCircularString *>( QgsGeometryFactory::geomFromWkt( wkt ) ) );
  QVERIFY( circularString.get() );                                              
  lineString.reset( circularString->curveToLine( 70 * M_PI / 180.0 ) );         
  QVERIFY( lineString.get() );                                                  
  //lineString->asWkt();                                                        
std::cout << "XXX --- " << lineString->asWkt().toStdString() << std::endl;

You can see the resulting line here:

Expected resulting line (obtained via PostGIS ongoing work https://gitlab.com/postgis/postgis/merge_requests/3) is this:

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