#include <OffsetSegmentGenerator.h>

Collaboration diagram for geos::operation::buffer::OffsetSegmentGenerator:

Public Member Functions
	OffsetSegmentGenerator (const geom::PrecisionModel *newPrecisionModel, const BufferParameters &bufParams, double distance)

bool	hasNarrowConcaveAngle () const

void	initSideSegments (const geom::Coordinate &nS1, const geom::Coordinate &nS2, int nSide)

void	getCoordinates (std::vector< geom::CoordinateSequence * > &to)

void	closeRing ()

void	createCircle (const geom::Coordinate &p, double distance)
	Adds a CW circle around a point. More...

void	createSquare (const geom::Coordinate &p, double distance)
	Adds a CW square around a point. More...

void	addFirstSegment ()
	Add first offset point. More...

void	addLastSegment ()
	Add last offset point. More...

void	addNextSegment (const geom::Coordinate &p, bool addStartPoint)

void	addLineEndCap (const geom::Coordinate &p0, const geom::Coordinate &p1)
	Add an end cap around point p1, terminating a line segment coming from p0. More...

void	addSegments (const geom::CoordinateSequence &pts, bool isForward)

Private Member Functions
void	addCollinear (bool addStartPoint)

void	addMitreJoin (const geom::Coordinate &p, const geom::LineSegment &offset0, const geom::LineSegment &offset1, double distance)

void	addLimitedMitreJoin (const geom::LineSegment &offset0, const geom::LineSegment &offset1, double distance, double mitreLimit)

void	addBevelJoin (const geom::LineSegment &offset0, const geom::LineSegment &offset1)
	Adds a bevel join connecting the two offset segments around a reflex corner. More...

void	init (double newDistance)

void	addOutsideTurn (int orientation, bool addStartPoint)

void	addInsideTurn (int orientation, bool addStartPoint)

void	computeOffsetSegment (const geom::LineSegment &seg, int side, double distance, geom::LineSegment &offset)
	Compute an offset segment for an input segment on a given side and at a given distance. More...

void	addDirectedFillet (const geom::Coordinate &p, const geom::Coordinate &p0, const geom::Coordinate &p1, int direction, double radius)

void	addDirectedFillet (const geom::Coordinate &p, double startAngle, double endAngle, int direction, double radius)

	OffsetSegmentGenerator (const OffsetSegmentGenerator &)

void	operator= (const OffsetSegmentGenerator &)

Private Attributes
double	maxCurveSegmentError
	the max error of approximation (distance) between a quad segment and the true fillet curve More...

double	filletAngleQuantum
	The angle quantum with which to approximate a fillet curve (based on the input # of quadrant segments) More...

int	closingSegLengthFactor

OffsetSegmentString	segList

double	distance

const geom::PrecisionModel *	precisionModel

const BufferParameters &	bufParams

algorithm::LineIntersector	li

geom::Coordinate	s0

geom::Coordinate	s1

geom::Coordinate	s2

geom::LineSegment	seg0

geom::LineSegment	seg1

geom::LineSegment	offset0

geom::LineSegment	offset1

int	side

bool	_hasNarrowConcaveAngle

int	endCapIndex

Static Private Attributes
static const double	OFFSET_SEGMENT_SEPARATION_FACTOR

static const double	INSIDE_TURN_VERTEX_SNAP_DISTANCE_FACTOR

static const double	CURVE_VERTEX_SNAP_DISTANCE_FACTOR

static const int	MAX_CLOSING_SEG_LEN_FACTOR = 80

static const double	PI

static const double	SIMPLIFY_FACTOR

Detailed Description

Generates segments which form an offset curve. Supports all end cap and join options provided for buffering. Implements various heuristics to produce smoother, simpler curves which are still within a reasonable tolerance of the true curve.

Author: Martin Davis

Definition at line 61 of file OffsetSegmentGenerator.h.

Constructor & Destructor Documentation

geos::operation::buffer::OffsetSegmentGenerator::OffsetSegmentGenerator	(	const geom::PrecisionModel *	newPrecisionModel,
		const BufferParameters &	bufParams,
		double	distance
	)

geos::operation::buffer::OffsetSegmentGenerator::OffsetSegmentGenerator ( const OffsetSegmentGenerator & )

private

Member Function Documentation

void geos::operation::buffer::OffsetSegmentGenerator::addBevelJoin	(	const geom::LineSegment &	offset0,
		const geom::LineSegment &	offset1
	)

private

Adds a bevel join connecting the two offset segments around a reflex corner.

Parameters

offset0	the first offset segment
offset1	the second offset segment

void geos::operation::buffer::OffsetSegmentGenerator::addCollinear ( bool addStartPoint )

private

void geos::operation::buffer::OffsetSegmentGenerator::addDirectedFillet	(	const geom::Coordinate &	p,
		const geom::Coordinate &	p0,
		const geom::Coordinate &	p1,
		int	direction,
		double	radius
	)

private

Adds points for a circular fillet around a reflex corner.

Adds the start and end points

Parameters

p	base point of curve
p0	start point of fillet curve
p1	endpoint of fillet curve
direction	the orientation of the fillet
radius	the radius of the fillet

void geos::operation::buffer::OffsetSegmentGenerator::addDirectedFillet	(	const geom::Coordinate &	p,
		double	startAngle,
		double	endAngle,
		int	direction,
		double	radius
	)

private

Adds points for a circular fillet arc between two specified angles.

The start and end point for the fillet are not added - the caller must add them if required.

Parameters

direction	is -1 for a CW angle, 1 for a CCW angle
radius	the radius of the fillet

void geos::operation::buffer::OffsetSegmentGenerator::addFirstSegment ( )

inline

Add first offset point.

Definition at line 124 of file OffsetSegmentGenerator.h.

void geos::operation::buffer::OffsetSegmentGenerator::addInsideTurn	(	int	orientation,
		bool	addStartPoint
	)

private

Adds the offset points for an inside (concave) turn

Parameters

orientation
addStartPoint

void geos::operation::buffer::OffsetSegmentGenerator::addLastSegment ( )

inline

Add last offset point.

Definition at line 131 of file OffsetSegmentGenerator.h.

void geos::operation::buffer::OffsetSegmentGenerator::addLimitedMitreJoin	(	const geom::LineSegment &	offset0,
		const geom::LineSegment &	offset1,
		double	distance,
		double	mitreLimit
	)

private

Adds a limited mitre join connecting the two reflex offset segments.

A limited mitre is a mitre which is beveled at the distance determined by the mitre ratio limit.

Parameters

offset0	the first offset segment
offset1	the second offset segment
distance	the offset distance
mitreLimit	the mitre limit ratio

void geos::operation::buffer::OffsetSegmentGenerator::addLineEndCap	(	const geom::Coordinate &	p0,
		const geom::Coordinate &	p1
	)

Add an end cap around point p1, terminating a line segment coming from p0.

void geos::operation::buffer::OffsetSegmentGenerator::addMitreJoin	(	const geom::Coordinate &	p,
		const geom::LineSegment &	offset0,
		const geom::LineSegment &	offset1,
		double	distance
	)

private

The mitre will be beveled if it exceeds the mitre ratio limit.

Parameters

offset0	the first offset segment
offset1	the second offset segment
distance	the offset distance

void geos::operation::buffer::OffsetSegmentGenerator::addNextSegment	(	const geom::Coordinate &	p,
		bool	addStartPoint
	)

void geos::operation::buffer::OffsetSegmentGenerator::addOutsideTurn	(	int	orientation,
		bool	addStartPoint
	)

private

Adds the offset points for an outside (convex) turn

Parameters

orientation
addStartPoint

void geos::operation::buffer::OffsetSegmentGenerator::addSegments	(	const geom::CoordinateSequence &	pts,
		bool	isForward
	)

inline

Definition at line 145 of file OffsetSegmentGenerator.h.

void geos::operation::buffer::OffsetSegmentGenerator::closeRing ( )

inline

Definition at line 111 of file OffsetSegmentGenerator.h.

void geos::operation::buffer::OffsetSegmentGenerator::computeOffsetSegment	(	const geom::LineSegment &	seg,
		int	side,
		double	distance,
		geom::LineSegment &	offset
	)

private

Compute an offset segment for an input segment on a given side and at a given distance.

The offset points are computed in full double precision, for accuracy.

Parameters

seg	the segment to offset
side	the side of the segment the offset lies on
distance	the offset distance
offset	the points computed for the offset segment

void geos::operation::buffer::OffsetSegmentGenerator::createCircle	(	const geom::Coordinate &	p,
		double	distance
	)

Adds a CW circle around a point.

void geos::operation::buffer::OffsetSegmentGenerator::createSquare	(	const geom::Coordinate &	p,
		double	distance
	)

Adds a CW square around a point.

void geos::operation::buffer::OffsetSegmentGenerator::getCoordinates ( std::vector< geom::CoordinateSequence * > & to )

inline

Get coordinates by taking ownership of them

After this call, the coordinates reference in this object are dropped. Calling twice will segfault...

FIXME: refactor memory management of this

Definition at line 105 of file OffsetSegmentGenerator.h.

bool geos::operation::buffer::OffsetSegmentGenerator::hasNarrowConcaveAngle ( ) const

inline

Tests whether the input has a narrow concave angle (relative to the offset distance). In this case the generated offset curve will contain self-intersections and heuristic closing segments. This is expected behaviour in the case of buffer curves. For pure offset curves, the output needs to be further treated before it can be used.

Returns: true if the input has a narrow concave angle

Definition at line 88 of file OffsetSegmentGenerator.h.

void geos::operation::buffer::OffsetSegmentGenerator::init ( double newDistance )

private

void geos::operation::buffer::OffsetSegmentGenerator::initSideSegments	(	const geom::Coordinate &	nS1,
		const geom::Coordinate &	nS2,
		int	nSide
	)

void geos::operation::buffer::OffsetSegmentGenerator::operator= ( const OffsetSegmentGenerator & )

private

Member Data Documentation

bool geos::operation::buffer::OffsetSegmentGenerator::_hasNarrowConcaveAngle

private

Definition at line 235 of file OffsetSegmentGenerator.h.

const BufferParameters& geos::operation::buffer::OffsetSegmentGenerator::bufParams

private

Definition at line 219 of file OffsetSegmentGenerator.h.

int geos::operation::buffer::OffsetSegmentGenerator::closingSegLengthFactor

private

The Closing Segment Factor controls how long "closing segments" are. Closing segments are added at the middle of inside corners to ensure a smoother boundary for the buffer offset curve. In some cases (particularly for round joins with default-or-better quantization) the closing segments can be made quite short. This substantially improves performance (due to fewer intersections being created).

A closingSegFactor of 0 results in lines to the corner vertex. A closingSegFactor of 1 results in lines halfway to the corner vertex. A closingSegFactor of 80 results in lines 1/81 of the way to the corner vertex (this option is reasonable for the very common default situation of round joins and quadrantSegs >= 8).

The default is 1.

Definition at line 203 of file OffsetSegmentGenerator.h.

const double geos::operation::buffer::OffsetSegmentGenerator::CURVE_VERTEX_SNAP_DISTANCE_FACTOR

staticprivate

Factor which controls how close curve vertices can be to be snapped

Definition at line 167 of file OffsetSegmentGenerator.h.

double geos::operation::buffer::OffsetSegmentGenerator::distance

private

Definition at line 215 of file OffsetSegmentGenerator.h.

int geos::operation::buffer::OffsetSegmentGenerator::endCapIndex

private

Definition at line 278 of file OffsetSegmentGenerator.h.

double geos::operation::buffer::OffsetSegmentGenerator::filletAngleQuantum

private

The angle quantum with which to approximate a fillet curve (based on the input # of quadrant segments)

Definition at line 184 of file OffsetSegmentGenerator.h.

const double geos::operation::buffer::OffsetSegmentGenerator::INSIDE_TURN_VERTEX_SNAP_DISTANCE_FACTOR

staticprivate

Factor which controls how close curve vertices on inside turns can be to be snapped

Definition at line 162 of file OffsetSegmentGenerator.h.

algorithm::LineIntersector geos::operation::buffer::OffsetSegmentGenerator::li

private

Definition at line 221 of file OffsetSegmentGenerator.h.

const int geos::operation::buffer::OffsetSegmentGenerator::MAX_CLOSING_SEG_LEN_FACTOR = 80

staticprivate

Factor which determines how short closing segs can be for round buffers

Definition at line 172 of file OffsetSegmentGenerator.h.

double geos::operation::buffer::OffsetSegmentGenerator::maxCurveSegmentError

private

the max error of approximation (distance) between a quad segment and the true fillet curve

Definition at line 178 of file OffsetSegmentGenerator.h.

geom::LineSegment geos::operation::buffer::OffsetSegmentGenerator::offset0

private

Definition at line 229 of file OffsetSegmentGenerator.h.

geom::LineSegment geos::operation::buffer::OffsetSegmentGenerator::offset1

private

Definition at line 231 of file OffsetSegmentGenerator.h.

const double geos::operation::buffer::OffsetSegmentGenerator::OFFSET_SEGMENT_SEPARATION_FACTOR

staticprivate

Factor which controls how close offset segments can be to skip adding a filler or mitre.

Definition at line 156 of file OffsetSegmentGenerator.h.

const double geos::operation::buffer::OffsetSegmentGenerator::PI

staticprivate

Definition at line 275 of file OffsetSegmentGenerator.h.

const geom::PrecisionModel* geos::operation::buffer::OffsetSegmentGenerator::precisionModel

private

Definition at line 217 of file OffsetSegmentGenerator.h.

geom::Coordinate geos::operation::buffer::OffsetSegmentGenerator::s0

private

Definition at line 223 of file OffsetSegmentGenerator.h.

geom::Coordinate geos::operation::buffer::OffsetSegmentGenerator::s1

private

Definition at line 223 of file OffsetSegmentGenerator.h.

geom::Coordinate geos::operation::buffer::OffsetSegmentGenerator::s2

private

Definition at line 223 of file OffsetSegmentGenerator.h.

geom::LineSegment geos::operation::buffer::OffsetSegmentGenerator::seg0

private

Definition at line 225 of file OffsetSegmentGenerator.h.

geom::LineSegment geos::operation::buffer::OffsetSegmentGenerator::seg1

private

Definition at line 227 of file OffsetSegmentGenerator.h.

OffsetSegmentString geos::operation::buffer::OffsetSegmentGenerator::segList

private

Owned by this object, destroyed by dtor

This actually gets created multiple times and each of the old versions is pushed to the ptLists std::vector to ensure all created CoordinateSequences are properly destroyed.

Definition at line 213 of file OffsetSegmentGenerator.h.

int geos::operation::buffer::OffsetSegmentGenerator::side

private

Definition at line 233 of file OffsetSegmentGenerator.h.

const double geos::operation::buffer::OffsetSegmentGenerator::SIMPLIFY_FACTOR

staticprivate

Use a value which results in a potential distance error which is significantly less than the error due to the quadrant segment discretization. For QS = 8 a value of 100 is reasonable. This should produce a maximum of 1% distance error.

Definition at line 289 of file OffsetSegmentGenerator.h.

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

OffsetSegmentGenerator.h

Public Member Functions

Private Member Functions

Private Attributes

Static Private Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation