geos::triangulate::polygon::PolygonEarClipper Class Reference

#include <PolygonEarClipper.h>

Public Member Functions
	PolygonEarClipper (std::vector< Coordinate > &polyShell)
void	setSkipFlatCorners (bool p_isFlatCornersSkipped)
void	compute (TriList< Tri > &triList)
std::unique_ptr< Polygon >	toGeometry () const

Static Public Member Functions
static void	triangulate (std::vector< Coordinate > &polyShell, TriList< Tri > &triListResult)

Detailed Description

Triangulates a polygon using the Ear-Clipping technique. The polygon is provided as a closed list of contiguous vertices defining its boundary. The vertices must have clockwise orientation.

The polygon boundary must not self-cross, but may self-touch at points or along an edge. It may contain repeated points, which are treated as a single vertex. By default every vertex is triangulated, including ones which are "flat" (the adjacent segments are collinear). These can be removed by setting setSkipFlatCorners(boolean)

The polygon representation does not allow holes. Polygons with holes can be triangulated by preparing them with PolygonHoleJoiner.

Author

Martin Davis

Constructor & Destructor Documentation

PolygonEarClipper()

geos::triangulate::polygon::PolygonEarClipper::PolygonEarClipper

(

std::vector< Coordinate > &

polyShell

)

Creates a new ear-clipper instance.

Parameters

polyShell

the polygon vertices to process

Member Function Documentation

setSkipFlatCorners()

void geos::triangulate::polygon::PolygonEarClipper::setSkipFlatCorners

(

bool

p_isFlatCornersSkipped

)

Sets whether flat corners formed by collinear adjacent line segments are included in the triangulation. Skipping flat corners reduces the number of triangles in the output. However, it produces a triangulation which does not include all input vertices. This may be undesirable for downstream processes (such as computing a Constrained Delaunay Triangulation for purposes of computing the medial axis).

The default is to include all vertices in the result triangulation. This still produces a valid triangulation, with no zero-area triangles.

Note that repeated vertices are always skipped.

Parameters

p_isFlatCornersSkipped

whether to skip collinear vertices

triangulate()

static void geos::triangulate::polygon::PolygonEarClipper::triangulate ( std::vector< Coordinate > &  polyShell, TriList< Tri > &  triListResult  )

static

Triangulates a polygon via ear-clipping.

Parameters

polyShell	the vertices of the polygon
triListResult	vector to fill in with the resultant Tri s

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

• PolygonEarClipper.h