Add QgsGeometry method to create wedge shaped buffers

Creates a wedge shaped buffer using circular strings, with
parameters for azimuth, wedge width (in degrees), outer radius
and inner radius.

Author: nyalldawson

python/core/geometry/qgsgeometry.sip.in

@@ -211,6 +211,24 @@ Creates a new geometry from a :py:class:`QgsRectangle`
 Creates a new multipart geometry from a list of QgsGeometry objects
 %End
 
+    static QgsGeometry createWedgeBuffer( const QgsPoint &center, double azimuth, double angularWidth,
+                                          double outerRadius, double innerRadius = 0 );
+%Docstring
+Creates a wedge shaped buffer from a ``center`` point.
+
+The ``azimuth`` gives the angle (in degrees) for the middle of the wedge to point.
+The buffer width (in degrees) is specified by the ``angularWidth`` parameter. Note that the
+wedge will extend to half of the ``angularWidth`` either side of the ``azimuth`` direction.
+
+The outer radius of the buffer is specified via ``outerRadius``, and optionally an
+``innerRadius`` can also be specified.
+
+The returned geometry will be a CurvePolygon geometry containing circular strings. It may
+need to be segmentized to convert to a standard Polygon geometry.
+
+.. versionadded:: 3.2
+%End
+
 
 
     void fromWkb( const QByteArray &wkb );

src/core/geometry/qgsgeometry.cpp

@@ -258,6 +258,39 @@ QgsGeometry QgsGeometry::collectGeometry( const QVector< QgsGeometry > &geometri
   return collected;
 }
 
+QgsGeometry QgsGeometry::createWedgeBuffer( const QgsPoint &center, const double azimuth, const double angularWidth, const double outerRadius, const double innerRadius )
+{
+  std::unique_ptr< QgsCompoundCurve > wedge = qgis::make_unique< QgsCompoundCurve >();
+
+  const double startAngle = azimuth - angularWidth * 0.5;
+  const double endAngle = azimuth + angularWidth * 0.5;
+
+  const QgsPoint outerP1 = center.project( outerRadius, startAngle );
+  const QgsPoint outerP2 = center.project( outerRadius, endAngle );
+
+  const bool useShortestArc = angularWidth <= 180.0;
+
+  wedge->addCurve( new QgsCircularString( QgsCircularString::fromTwoPointsAndCenter( outerP1, outerP2, center, useShortestArc ) ) );
+
+  if ( !qgsDoubleNear( innerRadius, 0.0 ) && innerRadius > 0 )
+  {
+    const QgsPoint innerP1 = center.project( innerRadius, startAngle );
+    const QgsPoint innerP2 = center.project( innerRadius, endAngle );
+    wedge->addCurve( new QgsLineString( outerP2, innerP2 ) );
+    wedge->addCurve( new QgsCircularString( QgsCircularString::fromTwoPointsAndCenter( innerP2, innerP1, center, useShortestArc ) ) );
+    wedge->addCurve( new QgsLineString( innerP1, outerP1 ) );
+  }
+  else
+  {
+    wedge->addCurve( new QgsLineString( outerP2, center ) );
+    wedge->addCurve( new QgsLineString( center, outerP1 ) );
+  }
+
+  std::unique_ptr< QgsCurvePolygon > cp = qgis::make_unique< QgsCurvePolygon >();
+  cp->setExteriorRing( wedge.release() );
+  return QgsGeometry( std::move( cp ) );
+}
+
 void QgsGeometry::fromWkb( unsigned char *wkb, int length )
 {
   QgsConstWkbPtr ptr( wkb, length );

src/core/geometry/qgsgeometry.h

@@ -256,6 +256,24 @@ class CORE_EXPORT QgsGeometry
     //! Creates a new multipart geometry from a list of QgsGeometry objects
     static QgsGeometry collectGeometry( const QVector<QgsGeometry> &geometries );
 
+    /**
+     * Creates a wedge shaped buffer from a \a center point.
+     *
+     * The \a azimuth gives the angle (in degrees) for the middle of the wedge to point.
+     * The buffer width (in degrees) is specified by the \a angularWidth parameter. Note that the
+     * wedge will extend to half of the \a angularWidth either side of the \a azimuth direction.
+     *
+     * The outer radius of the buffer is specified via \a outerRadius, and optionally an
+     * \a innerRadius can also be specified.
+     *
+     * The returned geometry will be a CurvePolygon geometry containing circular strings. It may
+     * need to be segmentized to convert to a standard Polygon geometry.
+     *
+     * \since QGIS 3.2
+     */
+    static QgsGeometry createWedgeBuffer( const QgsPoint &center, double azimuth, double angularWidth,
+                                          double outerRadius, double innerRadius = 0 );
+
     /**
      * Set the geometry, feeding in a geometry in GEOS format.
      * This class will take ownership of the buffer.

tests/src/python/test_qgsgeometry.py

@@ -4356,6 +4356,35 @@ def testClipped(self):
             self.assertTrue(compareWkt(result, exp, 0.00001),
                             "clipped: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
 
+    def testCreateWedgeBuffer(self):
+        tests = [[QgsPoint(1, 11), 0, 45, 2, 0, 'CurvePolygon (CompoundCurve (CircularString (0.23463313526982044 12.84775906502257392, 1 13, 1.76536686473017967 12.84775906502257392),(1.76536686473017967 12.84775906502257392, 1 11),(1 11, 0.23463313526982044 12.84775906502257392)))'],
+                 [QgsPoint(1, 11), 90, 45, 2, 0,
+                  'CurvePolygon (CompoundCurve (CircularString (2.84775906502257348 11.76536686473017923, 3 11, 2.84775906502257348 10.23463313526982077),(2.84775906502257348 10.23463313526982077, 1 11),(1 11, 2.84775906502257348 11.76536686473017923)))'],
+                 [QgsPoint(1, 11), 180, 90, 2, 0,
+                  'CurvePolygon (CompoundCurve (CircularString (2.41421356237309492 9.58578643762690419, 1.00000000000000022 9, -0.41421356237309492 9.58578643762690419),(-0.41421356237309492 9.58578643762690419, 1 11),(1 11, 2.41421356237309492 9.58578643762690419)))'],
+                 [QgsPoint(1, 11), 0, 200, 2, 0,
+                  'CurvePolygon (CompoundCurve (CircularString (-0.96961550602441604 10.65270364466613984, 0.99999999999999956 13, 2.96961550602441626 10.65270364466613984),(2.96961550602441626 10.65270364466613984, 1 11),(1 11, -0.96961550602441604 10.65270364466613984)))'],
+                 [QgsPoint(1, 11), 0, 45, 2, 1,
+                  'CurvePolygon (CompoundCurve (CircularString (0.23463313526982044 12.84775906502257392, 1 13, 1.76536686473017967 12.84775906502257392),(1.76536686473017967 12.84775906502257392, 1.38268343236508984 11.92387953251128607),CircularString (1.38268343236508984 11.92387953251128607, 0.99999999999999978 12, 0.61731656763491016 11.92387953251128607),(0.61731656763491016 11.92387953251128607, 0.23463313526982044 12.84775906502257392)))'],
+                 [QgsPoint(1, 11), 0, 200, 2, 1,
+                  'CurvePolygon (CompoundCurve (CircularString (-0.96961550602441604 10.65270364466613984, 0.99999999999999956 13, 2.96961550602441626 10.65270364466613984),(2.96961550602441626 10.65270364466613984, 1.98480775301220813 10.82635182233306992),CircularString (1.98480775301220813 10.82635182233306992, 0.99999999999999978 12, 0.01519224698779198 10.82635182233306992),(0.01519224698779198 10.82635182233306992, -0.96961550602441604 10.65270364466613984)))'],
+                 [QgsPoint(1, 11, 3), 0, 45, 2, 0,
+                  'CurvePolygonZ (CompoundCurveZ (CircularStringZ (0.23463313526982044 12.84775906502257392 3, 1 13 3, 1.76536686473017967 12.84775906502257392 3),(1.76536686473017967 12.84775906502257392 3, 1 11 3),(1 11 3, 0.23463313526982044 12.84775906502257392 3)))'],
+                 [QgsPoint(1, 11, m=3), 0, 45, 2, 0,
+                  'CurvePolygonM (CompoundCurveM (CircularStringM (0.23463313526982044 12.84775906502257392 3, 1 13 3, 1.76536686473017967 12.84775906502257392 3),(1.76536686473017967 12.84775906502257392 3, 1 11 3),(1 11 3, 0.23463313526982044 12.84775906502257392 3)))']
+                 ]
+        for t in tests:
+            input = t[0]
+            azimuth = t[1]
+            width = t[2]
+            outer = t[3]
+            inner = t[4]
+            o = QgsGeometry.createWedgeBuffer(input, azimuth, width, outer, inner)
+            exp = t[5]
+            result = o.asWkt()
+            self.assertTrue(compareWkt(result, exp, 0.01),
+                            "wedge buffer: mismatch Expected:\n{}\nGot:\n{}\n".format(exp, result))
+
     def testHausdorff(self):
         tests = [["POLYGON((0 0, 0 2, 1 2, 2 2, 2 0, 0 0))", "POLYGON((0.5 0.5, 0.5 2.5, 1.5 2.5, 2.5 2.5, 2.5 0.5, 0.5 0.5))", 0.707106781186548],
                  ["LINESTRING (0 0, 2 1)", "LINESTRING (0 0, 2 0)", 1],