Class QuadEdge

A class that represents the edge data structure which implements the quadedge algebra. The quadedge algebra was described in a well-known paper by Guibas and Stolfi, "Primitives for the manipulation of general subdivisions and the computation of Voronoi diagrams", ACM Transactions on Graphics, 4(2), 1985, 75-123.

Each edge object is part of a quartet of 4 edges, linked via their Rot references. Any edge in the group may be accessed using a series of Rot operations. Quadedges in a subdivision are linked together via their Next references. The linkage between the quadedge quartets determines the topology of the subdivision.

The edge class does not contain separate information for vertices or faces; a vertex is implicitly defined as a ring of edges (created using the Next field).

Inheritance

object

QuadEdge

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: NetTopologySuite.Triangulate.QuadEdge

Assembly: NetTopologySuite.dll

Syntax

public class QuadEdge

Properties

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DNext

Gets the next CCW edge around (into) the destination of this edge.

Declaration

public QuadEdge DNext { get; }

Property Value

Type	Description
QuadEdge

Remarks

Get the next destination edge.

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DPrev

Gets the next CW edge around (into) the destination of this edge.

Declaration

public QuadEdge DPrev { get; }

Property Value

Type	Description
QuadEdge

Remarks

Get the previous destination edge.

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Data

Gets or sets the external data value for this edge.

Declaration

public object Data { get; set; }

Property Value

Type	Description
object

Remarks

an object containing external data

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Dest

Gets or sets the vertex for the edge's destination

Declaration

public Vertex Dest { get; }

Property Value

Type	Description
Vertex

Remarks

Gets the destination vertex

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InvRot

Gets the dual of this edge, directed from its left to its right.

Declaration

public QuadEdge InvRot { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the inverse rotated edge.

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IsLive

Tests whether this edge has been deleted.

Declaration

public bool IsLive { get; }

Property Value

Type	Description
bool	true if this edge has not been deleted.

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LNext

Gets the CCW edge around the left face following this edge.

Declaration

public QuadEdge LNext { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the next left face edge.

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LPrev

Gets the CCW edge around the left face before this edge.

Declaration

public QuadEdge LPrev { get; }

Property Value

Type	Description
QuadEdge

Remarks

Get the previous left face edge.

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Length

Gets the length of the geometry of this quadedge.

Declaration

public double Length { get; }

Property Value

Type	Description
double

Remarks

Gets the length of the quadedge

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ONext

Gets the next CCW edge around the origin of this edge.

Declaration

public QuadEdge ONext { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the next linked edge.

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OPrev

Gets the next CW edge around (from) the origin of this edge.

Declaration

public QuadEdge OPrev { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the previous edge.

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Orig

Gets or sets the vertex for the edge's origin

Declaration

public Vertex Orig { get; }

Property Value

Type	Description
Vertex

Remarks

Gets the origin vertex

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RNext

Gets the edge around the right face ccw following this edge.

Declaration

public QuadEdge RNext { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the next right face edge.

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RPrev

Gets the edge around the right face ccw before this edge.

Declaration

public QuadEdge RPrev { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the previous right face edge.

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Rot

Gets the dual of this edge, directed from its right to its left.

Declaration

public QuadEdge Rot { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets or Sets the rotated edge

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Sym

Gets the edge from the destination to the origin of this edge.

Declaration

public QuadEdge Sym { get; }

Property Value

Type	Description
QuadEdge

Remarks

Gets the sym of the edge.

Methods

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Connect(QuadEdge, QuadEdge)

Creates a new QuadEdge connecting the destination of a to the origin of b, in such a way that all three have the same left face after the connection is complete. Additionally, the data pointers of the new edge are set.

Declaration

public static QuadEdge Connect(QuadEdge a, QuadEdge b)

Parameters

Type	Name	Description
QuadEdge	a
QuadEdge	b

Returns

Type	Description
QuadEdge	the connected edge

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Delete()

Marks this quadedge as being deleted. This does not free the memory used by this quadedge quartet, but indicates that this edge no longer participates in a subdivision.

Declaration

public void Delete()

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EqualsNonOriented(QuadEdge)

Tests if this quadedge and another have the same line segment geometry, regardless of orientation.

Declaration

public bool EqualsNonOriented(QuadEdge qe)

Parameters

Type	Name	Description
QuadEdge	qe	a quadedge

Returns

Type	Description
bool	true if the quadedges are based on the same line segment regardless of orientation

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EqualsOriented(QuadEdge)

Tests if this quadedge and another have the same line segment geometry with the same orientation.

Declaration

public bool EqualsOriented(QuadEdge qe)

Parameters

Type	Name	Description
QuadEdge	qe	a quadedge

Returns

Type	Description
bool	true if the quadedges are based on the same line segment

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GetPrimary()

Gets the primary edge of this quadedge and its sym. The primary edge is the one for which the origin and destination coordinates are ordered according to the standard Coordinate ordering

Declaration

public QuadEdge GetPrimary()

Returns

Type	Description
QuadEdge	the primary quadedge

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MakeEdge(Vertex, Vertex)

Creates a new QuadEdge quartet from Vertexo to Vertex d.

Declaration

public static QuadEdge MakeEdge(Vertex o, Vertex d)

Parameters

Type	Name	Description
Vertex	o	the origin Vertex
Vertex	d	the destination Vertex

Returns

Type	Description
QuadEdge	the new QuadEdge quartet

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SetNext(QuadEdge)

Sets the connected edge

Declaration

public void SetNext(QuadEdge next)

Parameters

Type	Name	Description
QuadEdge	next	edge

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Splice(QuadEdge, QuadEdge)

Splices two edges together or apart. Splice affects the two edge rings around the origins of a and b, and, independently, the two edge rings around the left faces of a and b. In each case, (i) if the two rings are distinct, Splice will combine them into one, or (ii) if the two are the same ring, Splice will break it into two separate pieces. Thus, Splice can be used both to attach the two edges together, and to break them apart.

Declaration

public static void Splice(QuadEdge a, QuadEdge b)

Parameters

Type	Name	Description
QuadEdge	a	an edge to splice
QuadEdge	b	an edge to splice

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Swap(QuadEdge)

Turns an edge counterclockwise inside its enclosing quadrilateral.

Declaration

public static void Swap(QuadEdge e)

Parameters

Type	Name	Description
QuadEdge	e	the quadedge to turn

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ToLineSegment()

Creates a LineSegment representing the geometry of this edge.

Declaration

public LineSegment ToLineSegment()

Returns

Type	Description
LineSegment	a LineSegment

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ToString()

Converts this edge to a WKT two-point LINESTRING indicating the geometry of this edge.

Declaration

public override string ToString()

Returns

Type	Description
string	a String representing this edge's geometry

Overrides

object.ToString()