geos::geomgraph::EdgeEnd Class Reference

Models the end of an edge incident on a node. More...

#include <EdgeEnd.h>

Inheritance diagram for geos::geomgraph::EdgeEnd:

Public Member Functions
	EdgeEnd (Edge *newEdge, const geom::Coordinate &newP0, const geom::Coordinate &newP1, const Label &newLabel)
	EdgeEnd (Edge *newEdge, const geom::Coordinate &newP0, const geom::Coordinate &newP1)
Edge *	getEdge ()
Label &	getLabel ()
const Label &	getLabel () const
geom::Coordinate &	getCoordinate ()
const geom::Coordinate &	getCoordinate () const
geom::Coordinate &	getDirectedCoordinate ()
int	getQuadrant ()
double	getDx ()
double	getDy ()
void	setNode (Node *newNode)
Node *	getNode ()
int	compareTo (const EdgeEnd *e) const
int	compareDirection (const EdgeEnd *e) const
virtual void	computeLabel (const algorithm::BoundaryNodeRule &bnr)
virtual std::string	print () const

Protected Member Functions
	EdgeEnd (Edge *newEdge)
void	init (const geom::Coordinate &newP0, const geom::Coordinate &newP1)

Protected Attributes
Edge *	edge
Label	label

Friends
std::ostream &	operator<< (std::ostream &, const EdgeEnd &)

Detailed Description

Models the end of an edge incident on a node.

EdgeEnds have a direction determined by the direction of the ray from the initial point to the next point. EdgeEnds are comparable under the ordering "a has a greater angle with the x-axis than b". This ordering is used to sort EdgeEnds around a node.

Constructor & Destructor Documentation

EdgeEnd() [1/2]

geos::geomgraph::EdgeEnd::EdgeEnd	(	Edge *	newEdge,
		const geom::Coordinate &	newP0,
		const geom::Coordinate &	newP1,
		const Label &	newLabel
	)

NOTES:

• Copies the given Label
• keeps a pointer to given Edge, make sure it's not deleted before the EdgeEnd.
• copies given Coordinates (maybe we should avoid that)

EdgeEnd() [2/2]

geos::geomgraph::EdgeEnd::EdgeEnd	(	Edge *	newEdge,
		const geom::Coordinate &	newP0,
		const geom::Coordinate &	newP1
	)

NOTES:

• keeps a pointer to given Edge, make sure it's not deleted before the EdgeEnd.
• copies given Coordinates (maybe we should avoid that)

Member Function Documentation

compareDirection()

int geos::geomgraph::EdgeEnd::compareDirection

(

const EdgeEnd *

e

)

const

Implements the total order relation:

a has a greater angle with the positive x-axis than b

Using the obvious algorithm of simply computing the angle is not robust, since the angle calculation is obviously susceptible to roundoff. A robust algorithm is:

• first compare the quadrant. If the quadrants are different, it it trivial to determine which vector is "greater".
• if the vectors lie in the same quadrant, the computeOrientation function can be used to decide the relative orientation of the vectors.

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The documentation for this class was generated from the following file:

• EdgeEnd.h