geos::noding::snapround::SnapRoundingNoder Class Reference

#include <SnapRoundingNoder.h>

Inheritance diagram for geos::noding::snapround::SnapRoundingNoder:

Collaboration diagram for geos::noding::snapround::SnapRoundingNoder:

Public Member Functions
	SnapRoundingNoder (const geom::PrecisionModel *p_pm)
std::vector< SegmentString * > *	getNodedSubstrings () const override
void	computeNodes (std::vector< SegmentString * > *inputSegStrings) override
Public Member Functions inherited from geos::noding::Noder
virtual	~Noder ()

Private Member Functions
void	snapRound (std::vector< SegmentString * > &inputSegStrings, std::vector< SegmentString * > &resultNodedSegments)
void	addVertexPixels (std::vector< SegmentString * > &segStrings)
void	addIntersectionPixels (std::vector< SegmentString * > &segStrings)
void	round (const geom::Coordinate &pt, geom::Coordinate &ptOut)
std::unique_ptr< std::vector< geom::Coordinate > >	round (const std::vector< geom::Coordinate > &pts)
void	computeSnaps (const std::vector< SegmentString * > &segStrings, std::vector< SegmentString * > &snapped)
NodedSegmentString *	computeSegmentSnaps (NodedSegmentString *ss)
void	snapSegment (geom::Coordinate &p0, geom::Coordinate &p1, NodedSegmentString *ss, size_t segIndex)
void	addVertexNodeSnaps (NodedSegmentString *ss)
void	snapVertexNode (const geom::Coordinate &p0, NodedSegmentString *ss, size_t segIndex)

Private Attributes
const geom::PrecisionModel *	pm
noding::snapround::HotPixelIndex	pixelIndex
std::vector< SegmentString * >	snappedResult

Additional Inherited Members
Protected Member Functions inherited from geos::noding::Noder
	Noder ()

Detailed Description

Uses Snap Rounding to compute a rounded, fully noded arrangement from a set of noding::SegmentStrings, in a performant way, and avoiding unnecessary noding.

Implements the Snap Rounding technique described in the papers by Hobby, Guibas & Marimont, and Goodrich et al. Snap Rounding enforces that all output vertices lie on a uniform grid, which is determined by the provided geom::PrecisionModel.

Input vertices do not have to be rounded to the grid beforehand; this is done during the snap-rounding process. In fact, rounding cannot be done a priori, since rounding vertices by themselves can distort the rounded topology of the arrangement (i.e. by moving segments away from hot pixels that would otherwise intersect them, or by moving vertices across segments).

To minimize the number of introduced nodes, the Snap-Rounding Noder avoids creating nodes at edge vertices if there is no intersection or snap at that location. However, if two different input edges contain identical segments, each of the segment vertices will be noded. This still provides fully-noded output. This is the same behaviour provided by other noders, such as noding::MCIndexNoder and noding::snap::SnappingNoder.

Definition at line 71 of file SnapRoundingNoder.h.

Constructor & Destructor Documentation

geos::noding::snapround::SnapRoundingNoder::SnapRoundingNoder ( const geom::PrecisionModel *  p_pm )

inline

Definition at line 140 of file SnapRoundingNoder.h.

Member Function Documentation

void geos::noding::snapround::SnapRoundingNoder::addIntersectionPixels ( std::vector< SegmentString * > &  segStrings )

private

Detects interior intersections in the collection of SegmentStrings, and adds nodes for them to the segment strings. Also creates HotPixel nodes for the intersection points.

void geos::noding::snapround::SnapRoundingNoder::addVertexNodeSnaps ( NodedSegmentString *  ss )

private

Add nodes for any vertices in hot pixels that were added as nodes during segment noding.

void geos::noding::snapround::SnapRoundingNoder::addVertexPixels ( std::vector< SegmentString * > &  segStrings )

private

Creates HotPixels for each vertex in the input segStrings. The HotPixels are not marked as nodes, since they will only be nodes in the final line arrangement if they interact with other segments (or they are already created as intersection nodes).

void geos::noding::snapround::SnapRoundingNoder::computeNodes ( std::vector< SegmentString * > *  inputSegStrings )

overridevirtual

Computes the nodes in the snap-rounding line arrangement. The nodes are added to the NodedSegmentStrings provided as the input.

Implements geos::noding::Noder.

NodedSegmentString* geos::noding::snapround::SnapRoundingNoder::computeSegmentSnaps ( NodedSegmentString *  ss )

private

void geos::noding::snapround::SnapRoundingNoder::computeSnaps ( const std::vector< SegmentString * > &  segStrings, std::vector< SegmentString * > &  snapped  )

private

Computes new segment strings which are rounded and contain intersections added as a result of snapping segments to snap points (hot pixels).

Parameters

segStrings

segments to snap

Returns

the snapped segment strings

std::vector<SegmentString*>* geos::noding::snapround::SnapRoundingNoder::getNodedSubstrings ( ) const

overridevirtual

Returns

a Collection of NodedSegmentStrings representing the substrings

Implements geos::noding::Noder.

void geos::noding::snapround::SnapRoundingNoder::round ( const geom::Coordinate &  pt, geom::Coordinate &  ptOut  )

private

std::unique_ptr<std::vector<geom::Coordinate> > geos::noding::snapround::SnapRoundingNoder::round ( const std::vector< geom::Coordinate > &  pts )

private

Gets a list of the rounded coordinates. Duplicate (collapsed) coordinates are removed.

Parameters

pts	the coordinates to round

Returns

array of rounded coordinates

void geos::noding::snapround::SnapRoundingNoder::snapRound ( std::vector< SegmentString * > &  inputSegStrings, std::vector< SegmentString * > &  resultNodedSegments  )

private

void geos::noding::snapround::SnapRoundingNoder::snapSegment ( geom::Coordinate &  p0, geom::Coordinate &  p1, NodedSegmentString *  ss, size_t  segIndex  )

private

Snaps a segment in a segmentString to HotPixels that it intersects.

Parameters

p0	the segment start coordinate
p1	the segment end coordinate
ss	the segment string to add intersections to
segIndex	the index of the segment

void geos::noding::snapround::SnapRoundingNoder::snapVertexNode ( const geom::Coordinate &  p0, NodedSegmentString *  ss, size_t  segIndex  )

private

Member Data Documentation

noding::snapround::HotPixelIndex geos::noding::snapround::SnapRoundingNoder::pixelIndex

private

Definition at line 77 of file SnapRoundingNoder.h.

const geom::PrecisionModel* geos::noding::snapround::SnapRoundingNoder::pm

private

Definition at line 76 of file SnapRoundingNoder.h.

std::vector<SegmentString*> geos::noding::snapround::SnapRoundingNoder::snappedResult

private

Definition at line 78 of file SnapRoundingNoder.h.

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

• SnapRoundingNoder.h