Counts the number of segments crossed by a horizontal ray extending to the right from a given point, in an incremental fashion. More...

#include <RayCrossingCounter.h>

Public Member Functions
	RayCrossingCounter (const geom::Coordinate &p_point)

void	countSegment (const geom::Coordinate &p1, const geom::Coordinate &p2)
	Counts a segment. More...

bool	isOnSegment () const
	Reports whether the point lies exactly on one of the supplied segments. More...

geom::Location	getLocation () const
	Gets the Location of the point relative to the ring, polygon or multipolygon from which the processed segments were provided. More...

bool	isPointInPolygon () const
	Tests whether the point lies in or on the ring, polygon or multipolygon from which the processed segments were provided. More...

Static Public Member Functions
static geom::Location	locatePointInRing (const geom::Coordinate &p, const geom::CoordinateSequence &ring)
	Determines the Location of a point in a ring. More...

static geom::Location	locatePointInRing (const geom::Coordinate &p, const std::vector< const geom::Coordinate * > &ring)
	Semantically equal to the above, just different args encoding.

Detailed Description

Counts the number of segments crossed by a horizontal ray extending to the right from a given point, in an incremental fashion.

This can be used to determine whether a point lies in a polygonal geometry. The class determines the situation where the point lies exactly on a segment. When being used for Point-In-Polygon determination, this case allows short-circuiting the evaluation.

This class handles polygonal geometries with any number of shells and holes. The orientation of the shell and hole rings is unimportant. In order to compute a correct location for a given polygonal geometry, it is essential that all segments are counted which

touch the ray
lie in in any ring which may contain the point

The only exception is when the point-on-segment situation is detected, in which case no further processing is required. The implication of the above rule is that segments which can be a priori determined to not touch the ray (i.e. by a test of their bounding box or Y-extent) do not need to be counted. This allows for optimization by indexing.

Author: Martin Davis

Member Function Documentation

◆ countSegment()

void geos::algorithm::RayCrossingCounter::countSegment	(	const geom::Coordinate &	p1,
		const geom::Coordinate &	p2
	)

Counts a segment.

Parameters

p1	an endpoint of the segment
p2	another endpoint of the segment

◆ getLocation()

geom::Location geos::algorithm::RayCrossingCounter::getLocation ( ) const

Gets the Location of the point relative to the ring, polygon or multipolygon from which the processed segments were provided.

This method only determines the correct location if all relevant segments must have been processed.

Returns: the Location of the point

◆ isOnSegment()

bool geos::algorithm::RayCrossingCounter::isOnSegment ( ) const

inline

Reports whether the point lies exactly on one of the supplied segments.

This method may be called at any time as segments are processed. If the result of this method is true, no further segments need be supplied, since the result will never change again.

Returns: true if the point lies exactly on a segment

◆ isPointInPolygon()

bool geos::algorithm::RayCrossingCounter::isPointInPolygon ( ) const

Tests whether the point lies in or on the ring, polygon or multipolygon from which the processed segments were provided.

This method only determines the correct location if all relevant segments must have been processed.

Returns: true if the point lies in or on the supplied polygon

◆ locatePointInRing()

static geom::Location geos::algorithm::RayCrossingCounter::locatePointInRing	(	const geom::Coordinate &	p,
		const geom::CoordinateSequence &	ring
	)

static

Determines the Location of a point in a ring.

This method is an exemplar of how to use this class.